Brangeta

Update: 6/17/21... I made a website where I wrote a guide to "how to install a transmission cooler on a Grand Prix GXP". Keeping the temperature low on your transmission fluid will prevent a lot of damage to your wallet and transmission. https://sites.google.com/view/grand-...grand-prix-gxp

I have a 2006 GXP I've had since January 2009 and have a ton of tips. I bought it at 26,000 miles and it currently has almost 77,000 miles.

The fuel filter isn't an inline one, it's in the fuel tank on the fuel pump, so it isn't something you can really swap out all that easily if at all w/o changing the fuel pump.

There's a little tiny Displacement on Demand filter underneath the oil pressure sensor you can replace for about $3 if I remember right (yeah, you can buy it from a GM dealership for about $3). If you decide to check it, you might as well have a new one on hand as well as a replacement oil pressure sensor in case you screw up the old one removing it. You can get both parts for under $70 from NAPA. Make sure not to overtighten the oil pressure sensor.

If it still has 4 cylinder mode (DoD or AFM) enabled, I would recommend disabling it via a tuner. There are many ways to do this, some are very cheap, but I use Diablosport InTune which I bought new several years ago for about $300. If you get that one, it makes you select a transmission tune, but after installing the engine tune (91 octane no DoD) you can click the X on the transmission tune to cancel the installation of it. I drive exclusively in manual/tapshift mode so I definitely don't benefit from their transmission tune. The Diabloesport InTune will also let you read "check engine" codes, which is handy.

Learn to drive in manual mode. Maybe it's just luck, but at nearly 77,000 miles I don't have any transmission issues. I did a poll one time in a different GXP group (that only got around 15 votes though...) and everybody who voted who has had to replace their transmission drives exclusively in Drive. I like manual mode because I can downshift to slow down and I don't have to suffer through the awkward, sloppy shifts that Drive gives. Since we only have 4 gears it's a real pleasure to use... it's not a chore like some of the modern 7 speed and 6 speed automatics.

Always carry a quart of 5w30 oil in your trunk in that little cargo net area. You'll want to keep an eye on your oil level when your DIC says it is below 70% oil life remaining. Even with DoD disabled, I still keep an eye on it. With it enabled, some people go through several quarts of oil between oil and filter changes. Our cars consume oil. I do almost entirely city driving and I go through at least 1 quart or more of oil every 3000 miles between oil changes (usually once a year for me).

I use Lucas Synthetic Oil Stabilizer in my oil. When I get an oil change, I wait until about 80% oil life remaining, I check the dipstick, and if the level is low enough, I add half a quart of that to my oil. It keeps the rockers quiet, which can chatter a bit, particularly in cold weather. It's around $17 a bottle.

Occasionally I use Lucas Complete Engine Treatment in my oil and gas, usually only if I find it on sale, and only in my oil if I haven't already used Lucas Synthetic Oil Stabilizer. It's around $10 a bottle. You can only add a few ounces to your oil, and only a little under a full bottle to your gas tank. It's supposed to clean and lubricate things. I only drive a few thousand miles a year and DoD was enabled until around 2014, so I like to try to make and keep everything clean inside.

Tell oil change (and other places) not to check your air filter if you have the factory OEM air box. It's basically impossible to correctly close it without removing it from the car. So you'll end up spending 30 minutes removing the entire thing from the car if someone decides to open it and try to look at the filter. I have a sticker on the black bar over it that says not to check it, that I maintain the air filter myself.

For transmission fluid changes, don't ever let anyone flush your fluids. The transmission pan needs to be removed, the filter needs to be changed, and I always pay the extra ~$60 for a new pan gasket. Never let anyone flush your transmission fluid! Change the fluid and filter every 15k to 20k miles if you regularly hit 200+ degrees.

Get a transmission fluid cooler that you zip tie to the front of the radiator if you regularly go on road trips or long commutes in your car. You need to prevent 210+ transmission fluid temperatures for prolonged time periods. I only have a 3 mile commute to work, so I don't have one. When I was working 16 miles from home though, I was heavily considering it, because the 45 minute drive was enough to get me to 190+ every time. 180 is considered operating temperature if I remember right, but 200+ is bad.

Coolant has to be changed every few years. DEXCOOL (orange coolant) lasts 5 years so get it changed every 4 or 5 years. If you or someone has converted to green coolant, you are going to have to monitor it more heavily. It has to be changed every 2 or 3 years. Green and orange do not mix. A little orange added to green coolant will produce what looks like peanut butter (after an unknown amount of time). I had to have the radiator in our '95 Z28 removed and replaced and all the hoses flushed with water because an oil change place (or dealership or other shop) must have topped up my green antifreeze with DEXCOOL, because it fowled and became peanut butter. It wouldn't go away and kept coming back. Personally, I recommend sticking with DEXCOOL forever and just make sure you get it changed every few years. It is easy to monitor on our GXPs since the overflow reservoir is so easy to open the cap on and look at.

I have some other good preventive tips as well.

The spring in the Head Up Display can break, so don't play with moving it up and down a lot. Find a setting you like and stay with it. I posted below how to fix the issue if you have it.

The front speaker in the dash has a habit of going bad. Someone told me about that in 2009, and so it's really easy to keep safe. You just slightly put your stereo's balance to the rear of the car. I don't remember the setting, but it's just barely off the center, balanced setting. It'll still sound good too.

I don't know about other owners, but when my wheels are dirty, my car drives crappy. I'm sensitive to differences, and everything just seems wrong about the way it drives when the wheels and struts are dirty. Ironically, I was complaining about my GXP feeling unstable and unsettling when cornering a month or so ago, and washing the car got rid of that. I'd love to be able to tell you what the problem is or how cleaning helps it, but I actually don't know.

Are there any parts that seem to break constantly on these cars?

Yeah, in my case, I've been through a few tie-rod ends and a couple motor mounts. At this point, I've had quite a lot of things replaced with new OEM parts up front. I can't think of a single problem with anything in the rear of the car so far. Everything has been up front and mostly related to steering.

Are there any common problems with hard to figure out solutions?

If your keyless entry remote has a button that stops working, it might be a combination of two things.
1. You need to solder the battery clip on better, because these were barely attached when brand new.
2. You need to replace the button pad, because your OEM original one has had the graphite wear down on the back of the button(s) and now it barely works. You'll find that the aftermarket bootleg/knock off remotes mostly suck and the OEM ones are EXPENSIVE and just going to have this same problem again. All you need to replace is the button pad, and if you want to replace the case too, you can.

Most of the aftermarket ones have buttons that stick out and are easy to accidentally press when your keys are in your pocket and you're walking. I found that the aftermarket bootleg that autodayplus sells on ebay
have button pads that are so similar to OEM that you can transfer them over to your OEM case. I highly recommend them.


OEM on the left, bootleg from ebay on the right

OEM on the left, bootleg from ebay on the right

OEM case with OEM buttons on the left, OEM case with bootleg buttons on the right

OEM case with OEM buttons on the left, OEM case with bootleg buttons on the right. This button pad I ordered without a case on ebay. The buttons fit terribly and stuck out so I couldn't keep my car from popping the trunk, setting off the alarm, locking, or unlocking when I'd walk away from it. These aftermarket button pads are common... much more common than ones that actually fit properly.

The70judge

Thanks for the tips... Just picked up a one owner 06 GXP and after I get rid of a couple codes and throw on an external tranny cooler I will have her out..

Retired -
1970 Orbit Orange GTO Judge
07 Antique Beige Grand Prix 3.8
06 Stealth Gray Grand Prix GXP

Brangeta

I forgot I made this thread. Glad to finally see a reply to it

Here's an update:

Head Up Display spring fix - this isn't preventive maintenance and can't be prevented. But it can be fixed pretty easily with a LOT of time and minimal tools.

The spring in my always garaged, 72,000 mile 2006 GXP's HUD finally broke off the plastic it was attached to. Diagnosing this is super easy. If you know your HUD was working the last time you drove, pretend you're as tall as an 8 year old and try to look at the windshield through the steering wheel--in other words: get low and look straight up. You'll see that your HUD didn't burn out, it is just displaying straight up. Your spring broke off. I used these directions, even though they weren't perfect: http://www.atthetipwebs.com/technolo...ctions/hud.htm

I literally fixed this last weekend, so it's very fresh in my mind. I ended up printing the website after modifying the code of it so the images would print big. I've attached a PDF of that to this post. Here's the list of my comments about what was wrong or what I experienced:

• Overall, the biggest problem is it says it takes like 3 hours. Including fixing the HUD and putting everything back together, I spent 12 hours or more over a Saturday and Sunday.
• Step 4 mentions you need to disconnect 1 wire. You have to disconnect 2 wires. 1 goes to your passenger airbag light, the other goes to your DIC.
• There's no reason whatsoever to do Step 6, just unscrew the screw in front of it.
• I don't understand why step 7 was listed, I don't think it was necessary but I did it anyway.
• Step 11 is horribly difficult. I used a Lowe's plastic card and Autozone plastic reward card to help lift the dash. Those clips are no joke. They are the same type as on the side dash panel in step 5. I've seen the official GM service manual for removing the HUD and it says not to pry with a screwdriver or anything else metal. It says to undo the 2 clips on the right and left of the HUD portion of the dash first and then the one in the middle of the HUD (closest to your face) which is total BS. I think you're going to want to go left to right a little at a time. Pertaining to the HUD portion, start on the left, move to the middle, and then the right. Or vice-versa. I cracked my dash popping the clips out, so that sucked. But to complete step 12, I had to get my fiance to come over and help me. I struggled with it by myself for almost 2 hours. You need someone with very small hands to turn the security light and light sensor a 1/4 turn. And you need someone with very small hands to push down on the plastic that is under the dash while they pull the dash upward and out. In my case, the foam rubber was stuck underneath the windshield and a part of it had to be torn off to get the dash out. It took over an hour, maybe 2 hours to try to get this out together. I ended up with 1 large crack in my dash, 2 small cracks, and 2 broken pegs. The dash is made of ABS plastic, so you can repair it with a chemical weld. This product isn't made anymore, but it's called Ambroid ProWeld. I used it to nearly flawlessly repair the cracks. You cannot glue ABS unless your glue is specifically made for ABS and you shouldn't try to Fiberglass it or anything like that. Ambroid ProWeld isn't made for using as a glue, it's made for causing ABS cracks to chemically seal themselves, so the pegs didn't get glued on well. I should have gotten some ABS glue for plumbing or something... but I didn't want to go to Lowe's to see if they had ABS plumbing glue. Also, FYI, Ambroid ProWeld is a liquid that you brush on like nailpolish, except it is as thin as brushing water and very toxic. You have to be well ventilated outside to use it.
• Step 12 is simple. So are steps 13 through 16.
• Step 17 is tricky only because of how tiny this plastic piece is. Your margin for error is very small. This piece is made of POM, which is a type of high tech plastic that (based on what I read) is basically very difficult to repair. It reminds me of Lego plastic. So anyway, repairing the plastic in a reliable way is impossible. You can't super glue it or necessarily have faith in epoxy. It may not stick, because this plastic is meant to be hard to stick to. So you're going to have to drill a tiny 1/16" hole next to the broken part, but there's a bar behind it, so you have to get it placed exactly so or you're going to drill through a structural part of the piece. I put the piece in my vice with rubber grips on it and drilled it after etching a tiny dent in the piece with a sharp nail so the drill bit wouldn't slip. And because the worn/broken area was so large and it made me so nervous, I went ahead and repaired the original area with epoxy just to put my nerves at ease and maybe provide some structural strength. It was too small for me to epoxy a small metal washer (which I didn't have) around the hole, and I didn't have faith epoxy would hold it, so this ended up being a repair that I hope I get another 12 years out of before the spring eats through the hole I just made too.
  
• Steps 18 through 20 are super easy.
• Putting everything back together took 4 hours for my fiance and me to do. About an hour was spent trying to get the light sensor back in the dash though. The red security light was bad enough, but my God, what a horrible experience. I'd recommend a long pair of needle-nose vice-grips for holding the sensor and trying to turn it. I didn't have a pair that was long enough, so it was difficult. I can't tell you how hard this was to do. We finally resorted to what I hoped to avoid and I pushed up on the dash toward the windshield while my fiance used her small hands to get the sensor into the hole and turn it. We ended up breaking the 2 pegs off I attempted to glue on and recracked the big crack I fixed earlier. And after that was done, the act of snapping the dash back down into place reopened that large crack a lot more. And the gap is large enough that it can't be pushed back together for another dose of Ambroid. But at this point, I don't care. I'm glad my HUD works again. The rest of the reassembly is pretty simple.

BlackApex

I wonder if the oil consumption was an issue depending no how the engine was used/abused from day one? I have an '07 with 68k on it and uses no oil whatsoever. Even with DoD enabled. Car came from Victoria, British Columbia, which has a lot of retired folks, so car didn't seem to have been abused at all. I know a lot of people on this forum have oil issues, and some were recalled depending on usage, so who knows. Luckily, mine seems good...so far.

I also have a Diablo InTune3 Platinum to disable the DoD, and I'm currently running the 94 tune with hard shift transmission programming. I seem to think the shift change also changes the shift when using TapShift, but I could be wrong in that...I've only tried it a couple times, and never really used it much before.

Thanks for the 'heads-up' on the HUD!

Brangeta

Writing this quickly before I leave work... Is it possible that your GXP had the TSB (technical service bulletin) taken care of for the oil consumption? There wasn't technically a "recall" I don't think. GM just created a new part... like an oil pan... (or something), but if you wanted it, you had to pay to have it done. I never paid to have it done, so I don't have it. My GXP has gotten bad gas mileage the entire time I've owned it since January 2009. Both with DoD enabled and without. Without I average 12.8 mpg. With it, I don't remember, as it has been many years since I have used it. I'm currently at 72,000 miles. I've consumed oil the entire time, but back in the day, I didn't know it, until I got my first "low oil" light on a road trip.

I love Tap Shift. It's one of my favorite things about the car. And unlike all of the GM cars from the last 10 years, our steering wheel buttons actually make sense. I hate all the GM steering wheels from the last 10 years with their horrible "seek" up/down switch on the right-hand side of the steering wheel. Garbage.

BlackApex

It's possible the bulletin was done, but I wasn't told about it, so I assume not. I'm about to change the oil before storing the car for winter. In 5000 miles, the oil hasn't dropped at all on the dipstick.
I'm also averaging 20.9MPG right now with city and highway driving, and tuned to 94 octane. And with the tune, I tend to accelerate faster now just for the fun of it. I don't floor it, but driver it quicker than before I tuned it for sure. Odd you're getting such bad mileage...unless you're all city driving.
And...I'm actually running 255/35ZR20 Continental ExtremeContact Sport tires all-round, so that would probably not help my mileage any being a sticky tire...obviously I'm not hard enough on the throttle...

higsy

Nice to see people taking meticulous care of there car. I'm an original 06 owner and don't ever see getting rid of the car.im only at about 70000k and only drive in the summer.

Brangeta

I'm pretty heavy on the throttle and almost exclusively city driving in Dallas, so my gas mileage is partially my fault. Most people in Dallas drive aggressively. Moreover, in manual mode (tapshift), in order to get a smooth upshift from 1st to 2nd, you need to be over half throttle, or you'll get that forward motion (with your body) that driving in drive will give you on that upshift. You know... where your head nods forward as the acceleration briefly turns to deceleration. I don't really pay attention anymore; shifting into 2nd is like second nature, but I suppose it's a little over halfway to the floor to get a nice shift. I've been driving my GXP since I got it in January 2009, nearly the entire time in only manual mode. The 2nd to 3rd and 3rd to 4th upshifts don't care as much about how hard you're pushing the gas, they are pretty smooth no matter what. If I remember correctly, the gear ratios for 3rd and 4th are barely any different from each other. But 4th is only for shifting into over 50 mph unless you're just throwing it into 4th and coasting to a far off red light or stop sign. If that's the case, I'll do that anywhere over I guess 40 mph and just let off the gas completely as long as I'm not going uphill. And, of course, 2nd gear doesn't come close to redlining until around 90 mph, so if I'm getting on the highway from a red light, I just stay in 2nd until after I've hit 60 or 70 mph. By no means do I downshift to 2nd from a speed of like 70 to accelerate. I'll go down to 3rd if I really need to pass someone or drive defensively, but it would be unsafe to drop to 2nd gear from that speed in my opinion.

The owners manual is surprisingly helpful in teaching a person how to shift in manual mode, but it really comes down to practice and experience. It's not difficult by any means, but shifting smoothly will take at least a few months of experimentation.

Gee... I got off on a tangent. Oh well, I had fun typing it.

Red_Zone

From a dead stop in tap shift, you can start in 2nd gear.

And once the 5.3 receives a tune, a better transmission cooler, a deeper transmission pan, an electric exhaust cutout, a turbo, an intercooler and preferably also more or less a meth injection, you find you gain access to a much safer and broader range of available power and control when compared to the stock car. 2nd gear becomes more or less home, if you want it to be.

Ultimately you end up with a decent street car. One that can use just one gear, second gear, to consistently run 5 second 0-60 times and reach 90 MPH top speeds.

These transmissions suck? So why shift? Turbos solve the worlds problems.

Brangeta

I updated my first post with some more info, but it said it was too long, so here's some more:

If your Drivers Information Center (DIC) says

Service Brake System... Service ABS System... Service Traction System... Service Stability System... Service Variable Effort Steering... and then repeats, your EBCM has gone bad. Also known as the ABS module. You can either pay a dealership to replace it for you, for the mighty sum of $1200+ like I did, or, remove it yourself and mail it to a place like https://modulemaster.com/rebuilds/sh.../abs-bosch-53/ to get repaired for under $200.

If your DIC says

Service ABS System... Service Traction System... Service Stability System... and then repeats, it can be one of your hubs... the bearings... or the wire that goes to the brakes. Supposedly a code will show up that will point you to the issue, however, but you'll need a more expensive scan tool that will display ABS codes than the typical $50 one. A Blue Driver will scan codes like this. I've only had this message come up one time and never again.

DropDeadRed

Finally getting around to reading this thread after you linked it on a post I had about rust. At least it's giving me a little hope... I'm the one who overpaid and then had to put in the brand new tranny? Basketball goal fell over on it during a windstorm and I had just gotten it back from the collision shop when tadaaaa - low oil level light! Had kiddo pull over and check the oil after a few minutes, and I thought it was reading fine. It's been parked for the past two weeks while we were making sure the paint dried and we had time to get it to the shop. Mechanic said the oil isn't even touching the dipstick, but it's bone dry underneath and he doesn't see any leaks.

Cue my showing him a picture of the spark plug a friend and I changed a few weeks ago after the check engine light came on and diagnosed a cylinder 4 misfire. It was as black as my heart. Mechanic looked like I just told him death was coming for him, and after he walked my phone/picture back to the other mechanic, the "HOLY CRAP!!!" that followed was unmistakable. Now they're saying oil consumption, and that the engine is doomed. They mentioned a possible TSB that involves engine cleaner, but said it might not work and would cost $700-800. Currently they have us on a SeaFoam routine and documenting the oil level at each gas fill up. I did contact a shop that does tuning and am looking into having the DoD delete done... Just hoping it's not too late.

By my guess, kiddo has put nearly 1800 miles on it since the tranny/oil pan gasket replacement on October 1st. That's when it had its last oil change. I think the mechanic said he only had to add a quart of oil to get it back where it should be, but I'm assuming it's missing more than 1 quart to not be touching dipstick?

I need a little hope if anyone has any lying around. I assume if the engine really is doomed, then keeping an eye on the oil level and adding as needed will only work for so long? I just need it to last until it gets paid off... And that tranny too! Ugh.

Denis123

Cool!

Brangeta

Oops, I haven't been on here in a couple months. I edited your post above to trim it down to what I wanted to comment on...

Low oil will certainly damage your piston rings, but I don't know if you could say your engine is shot.

I only drive my GXP around 4,000 miles a year, so I get an oil change around 1 time a year and I add oil to the engine at least 3 times before I'm ready for my annual oil change at around 30 to 40% oil life remaining. These days I typically add it before the "low oil level" message/symbol comes on*. It took me a few years to learn when it usually starts running low, and these days I can actually hear/feel that the car probably needs more oil just when I'm driving the car slowly over a speed bump. I don't have my maintenance booklet on me, but I think I check the oil at "oil life remaining" 77% and typically add at least half a quart of oil. The netted cargo area in the trunk holds a bottle of oil pretty well FYI. Honestly, I add Lucas Synthetic Oil Stabilizer instead of oil if I'm at about 80% oil life remaining and I'm at home, because it helps ensure the rockers stay quiet. I don't carry the Lucas in my trunk.

*Note: the low oil level message on our GXPs comes on when you still have SOME oil on the dipstick. It's typically barely in the cross hatched area, but it's still in the area. If the oil level is BELOW the cross hatched area, you need to add at least 1 quart of oil. This is open to discussion, but I would say that if "low oil level" comes up, it is ideal that you pull over within a mile and top it up... and certainly keep the RPMs low until you do fill it up.

The original owner of my car did rely on the oil life monitor to tell them to change the oil. I know this, because they actually wrote their oil changes down in the owner's manual. I don't know if they had to add oil back then, but I assume they did. But they did wait until 0% oil life a few times. The oil life monitor is a terrible thing to rely on for our cars, because (1) you'll certainly have had to have added oil a few times, (2) the color of your oil would be really black by 0% (probably not when the first owner of my car was at like 10,000 miles though...), (3) oil changes aren't THAT expensive. The problems from dirty oil, burnt oil, or low oil are a lot more expensive than an oil change. Like I said, I get it changed at around 40% life typically.

I've copy and pasted this from the owner's manual:

I personally believe those are good instructions.

Obviously, I ignore and disagree with this:

The Lucas Synthetic Oil Stabilizer really quiets down the rockers a lot, and makes the engine run really smooth. People who run synthetic oil might already have plenty of protection, but I just pay for the cheapest dinosaur oil changes I can get, and refill with Castrol 5w30.

The 5.3L LS4 engine holds 6 qts of oil according to the owner's manual. I believe slightly under that, however. More like 5.5 qts...? So if you are a quart low, you're almost 20% low on oil.

AndrewGXP

Im a tech and pretty OCD about our car because its our only one and its a 2006 that is a daily driver at 201,000+ miles now.
About the oil consumption, I now believe it is the PCV system allowing the intake to suck oil out of the air in the valve covers or the oil level sensor.
The LS4 has 2 of these pcv systems, front valve cover to center top of intake mani, rear valve cover to throttle body area, post throttle/pre intake mani.
I installed a catch can between the front valve cover and the pcv connector on top of the intake. After 2 weeks of daily driving, about 200-300 miles, the catch can has a cup(kitchen measuring cup) or so of oil inside.
I plan to install a second catch can on the rear cover piping.
Im also suspicious of the oil level sensor on bottom of pan, when I installed our transmission I replaced oil pan gasket with the TSB gasket, hardly a difference in oil consumption,
anyways, the level sensor float was dark like oil and I suspect it does not float as well as it should. Will be changing soon and posting about it, PM if I havent or if you need any info.

I recommend Amsoil OE 5w30 or better, our 06 GP GXP loves the stuff.
At 200,000+ miles Ive only heard lifter tick on 2 different really cold starts, below 35f, and it lasted for not even 2 seconds each time.
More consistent cold pressure, oil runs cooler, and its American synthetic.
Get the preferred membership and OE is only $5.45 from their website.
Change the filter under oil pressure sensor at least every 3 oil changes. Theyre cheap, you'll just need a 1-1/16" deep socket for the oil sensor.

Id also recommend Amsoil transmission fluid, I may be a fanatic but at 35,000 miles on our TEP HPS1 the fluid was still ruby red and smelled barely used, unfortunately the cooler clogged and torque converter blew a seal.
If you use an external cooler I would recommend back-flushing it every 10-15k miles, or run 2 cooler in parallel, which is my plan if shop tells me its just an external seal.

Brangeta

Interesting. I probably wrote this in a post above, but even with DoD tuned out I still consume oil. Perhaps not as much as I used to with DoD active, but even though I write down when, at what mileage, and approximately how much oil I add, I don't do the math to calculate anything with what I write down. There was a TSB #11-06-01-007 meant to correct "Engine Oil Consumption with Active Fuel Management" from Nov 22, 2011, but the labor time for "warranty" purposes was 6.5 hours, but off warranty, my dealer quoted me 11.5 hours, so I certainly never paid for it to be done. It wasn't a recall in case anyone is wondering. The oil pan gasket is part # 12643081 and GM will use part # 88861802 (in Canada, 88861804) to clean the upper engine and fuel injectors. Just giving that info, since I have it in front of me right now...

I don't know if I said this anywhere here before, but I use a DiabloSport InTune to turn off DoD. For the past 2 (maybe more) years, I remove my tune (and thus turn DoD back on) the month before I need to get a state inspection, because my O2 Sensor and Evap System have both displayed as Not Ready and caused me to fail my state inspection. When this first happened in 2019, I hadn't changed the battery, undid a battery cable recently, or done any work to my car for several months, so I came to the assumption that the tune was the culprit. So I uninstalled the tune, drove a few weeks, came back for another inspection, and my O2 was Ready. You're allowed 1 Not Ready in Texas to still pass inspection. Just an interesting tidbit that might help someone someday.

Since I have a Blue Driver these days, I should have just checked in November 2020 to see if my O2 was Ready myself, before removing the tune, but I didn't think of that. I removed the tune out of superstition/conclusion from the previous year.

I have my maintenance binder in front of me right now as well as my notebook from the car. I'm curious if there's a pattern... this is going to get scientific, so bear with me if anybody reading this cares to actually read this... I'd just skip to the end if I was reading this...

2020: O2 Ready, Evap Not Ready. Tune was not installed at this time and I had driven 315 miles with DoD on before I went for my inspection.

2019b: O2 Ready, Evap Not Ready. Tune was not installed at this time and I had driven 138 miles with DoD on before getting this second inspection.
2019a: O2 Not Ready, Evap Not Ready. I know for a fact the tune was installed at the time. I had 2 Not Readies, so I failed my inspection. I uninstalled the tune, did the ridiculous driving pattern I read about online, and (read line above). I don't know why this happened. It had been 1209 miles since I had my water pump and power steering pump replaced before they failed (and the battery was possibly undone during that). The only thing between that and an inspection was an oil change 844 miles before the inspection. This was a true mystery. I had a Facebook post about this, and I said I didn't believe I had ever removed my tune for an inspection before, but was going to try it.

2018: O2 Not Ready, Evap Ready. Don't know if tune was installed, but I didn't make a note about removing it. I would assume it was installed based on other maintenance notes that year. The O2 not being ready might be due to having the battery undone for several days as I fixed my HUD spring in October, and I put only 903 miles on the car from then till my inspection, and I think they were likely almost all short drives. With that many miles... I think the battery being unhooked is irrelevant though. No clue why EVAP was ready, but it was. That's a bigger mystery.

2017b: O2 Ready, Evap Not Ready. Passed inspection this time after putting 188 miles on the car. I didn't make a note about removing my tune, so it was probably installed, even though this one matches the pattern (above) of times I had the tune turned off and got an inspection.
2017a: O2 Not Ready, Evap Not Ready. This was possibly because I had changed my battery 531 miles previous to my inspection, and possibly none of that driving was on the highway. My notes don't say I removed the tune, so it might have been installed or might not have been. I had a lot of work done in 2017 (alternator changed twice, for example) by the dealer before I changed my battery, and I'd always uninstall the tune before taking it to them since they'd hook up to the ODBII port every time. Regardless, the battery change was the most recent thing I did before my inspection, and I had driven 531 miles in the city since then.

2016: O2 Not Ready, Evap Ready. The tune was likely installed.

2015: O2 Not Ready, Evap Ready. My tune was definitely installed at the time, so DoD was turned off.
********In November 2015 I ordered a DiabloSport InTune and turned off DoD to prevent issues DoD causes.********

2014: O2 Ready, Evap Ready. I didn't have a tuner yet.

2013: O2 Ready, Evap Ready. I didn't have a tuner yet.

2012: O2 Ready, Evap Ready. I didn't have a tuner yet. Failed my inspection due to window tint laws in Texas becoming stricter though lol. Had to remove my front window tint to pass.

2011: O2 Ready, Evap Ready. I didn't have a tuner yet.

2010: O2 Ready, Evap Ready. I didn't have a tuner yet.

2009: O2 Ready, Evap Ready. I didn't have a tuner yet.

So... my results aren't statistically significant since this is a sample size of just 1 person.. and there's a disagreement in the pattern. The age and mileage of my car may have more to do with the Not Ready stuff, so I don't think correlation = causation. If you remove the times I failed my inspection and only look at the others... the times when I had the tune installed (or likely had it installed), O2 would be Not Ready and Evap would be Ready. The times when I had removed the tune, it would display O2 Ready, Evap Not Ready. The exact opposite. If all things were equal, the O2 and Evap should both be ready when the tune isn't installed and I'd test just like I did from 2009 to 2014. If I assume the tune is 100% responsible for O2 Not Ready (which 2015 and 2016 support), then that would suggest that I did have my tune installed in 2018.

Overall, I think this analysis was a waste of time. I'm best off just plugging in my Blue Driver the month before my inspection and make sure at least O2 or Evap is ready.

AndrewGXP

I take it you have no stored or pending OBD codes, so that narrows it down to whether or not the ecm has been able to complete its "Drive cycle tests".
I have no experience with tuners, but know a little.
Does the tune/tuner interfere with or disable certain "checks" or "cycle tests"?
My advice is to contact someone that creates/sells tunes for the car and ask them if the tune you have could be interfering or "not allowing" the ecm to complete its drive cycle tests.

I believe some chips can "intercept" EVAP or Emissions/O2 system communication to enable/allow the ecm to run correctly with the tune in place without setting off the MIL.
Seeing as you dont need a chip, the ecm being configured directly,
I would say the tune has disabled some check or has "locked in"/programmed some configuration number or table to hold at a static number.
And I think when the ecm initiates these tests it may try to do some fuel trimming to determine O2 functionality.
I do know the EVAP and O2 drive cycle tests depend on certain engine conditions, temperature, speed, and load, over different mph drives, example being like 20-30minutes at sustained over 55mph but below 75mph. Not exact numbers there but there are multiples of those maybe one like 10-15minutes sustained driving at 25+mph but below 40mph, I hope someone corrects me here but I believe there are 4 different speed ranges it tests at, each needing the engine to be at operating temp, which who knows if thats a programmed 190 or higher, but seeing as stock thermostat 187 maybe your engine isnt getting hot enough to trigger a proper drive cycle?
Gotta love and hate GM for these cars.

Brangeta

It's been a few weeks, but I did all of the scans a Blue Driver allows (which includes ABS codes--which I'm mentioning not in regard to this, but in regard to why I used my Blue Driver), and I don't have any codes, errors, or problems for anything stored in my car. Zero. I didn't scan for inspection stuff though, because I was trying to determine if I just hit a bump in the road funny, or if I had an issue. I had the Service ABS System... Service Traction System... Service Stability System... and then repeats message come up, which "can be one of your hubs... the bearings... or the wire that goes to the brakes." according to what I wrote above. It hasn't returned, so it might have been a glitch from hitting a dip in the road funny. That's off-topic info though... so let's get back on topic...

I don't know if the tuner interferes with anything beyond cruise control. For whatever reason, if you have your GXP tuned by a DiabloSport InTune, you will not have cruise control without turning off traction control. Don't know why. If I remove the tune, I have cruise control with traction control, so no lingering oddity. In regard to everything you mentioned about everything else... that's honestly beyond my knowledge. I don't know. I just bought the $330 tuner in 2015 to simply turn off DoD and do nothing else with. I was having noisy rockers and dirty, burnt oil at I think around 53,000 miles and I started believing the legends I'd read concerning "DoD and AFM will destroy your engine," so I decided to believe it. I don't want to type forever today, so I'll keep this short. I don't have that dirty oil or chattering rockers issue anymore, probably, in part or entirely, due to some other things I already mentioned in this thread concerning Lucas products, turning off DoD, and having my engine flushed with transmission fluid right after I had an oil change, and right before I had another oil change 5 minutes later. The flush didn't get rid of the chatter from my rockers, but I have had much cleaner oil the past 5 years since doing that. The chatter has gone away due... I imagine... mostly in part to the Lucas Synthetic Oil Stabilizer and maybe partly due to the upper cylinder and fuel injector cleaner removing some gunk so the Lucas could get up there better. None of this stuff I just said is scientific, but in my case, it seems to have worked. I use regular Castrol 5w30... and once that burns off a bit, I add some Lucas.... I use fuel injector and upper cylinder cleaner with pretty much every other tank of 93 octane I get the past 2 or 3 years. Without taking the engine apart, I am simply shooting in the dark, but the expense is pretty low of getting these products and it seems to help the car run a bit cleaner and probably/hopefully extends the life of the engine. I'm at around 78,000 miles these days. Not exactly pushing the limits of the engine, but that's my story.

Part of the reason my engine has always had a little dirtier oil than others is the fact that most of my drives are short (I have lived 2 miles from work the past 5 years, for example) and so the car doesn't get very hot or run for very long. It gets driven around 30 minutes max, but more commonly, 8 minutes twice a day. We don't use it for road trips since I never installed a transmission cooler, so the furthest it gets driven in a single drive is around 40 miles. Anybody who commutes 15 miles or more definitely needs a transmission cooler of some type. They just do.