VerdeZ28

I have been struggling with this issue for a while now. My 2002 Z06 starts up fine and runs for a while. When temps get around 150 or so it will suddenly stop running. Particularly it will read 0 rpm and stop running even if the car is rolling in gear with the key in the ON position. Sometimes it takes a few seconds or a minute after this happens till I can crank it up again. Once I do it will run fine pretty much indefinitely until I let it sit again, completely cool down and it will happen again the next time I start it.

I thought it has to do something with it transitioning from open loop to close loop, but I am not sure how to verify this. Also I replaced the crank positioning sensor since I got a code saying that it was having slow response. While I was in there I noticed that the wires going to the crank shaft sensor were in bad shape because of my long tubes so I repaired that too. I thought all of that would do the trick but it did not. I will add though to prevent future damage to these wires i zip tied them to a ground that goes to the block. Not sure if there is enough "noise" there to mess with the Crank position sensor signal but I would think if it were an issue, it wouldn't run at all. Anyways When it shuts off suddenly like that, if i run the codes right after it happens I get P1637H.

I'd appreciate any help with this. Car is starting to feel dangerous to take out because having it suddenly shut off in traffic is not fun.

Also I haven't done a crank relearn with the new sensor so Ill do that and see if it helps. Also not sure if it matters but when the car is off, the DIC reads around 11.7V but when its running it reads 13.8-14.1V. Also my horn does not work.

bwolfZ28

iTrader: (40)

Are the wires chewed up or melted in any way that they can maybe arc on each other?

ChopperDoc

From what I found on another forum, it says a 1637 is Generator L-Terminal Circuit.

I would check all of your main power wires, especially the one from the battery to the starter. Mine rubbed just a little on my A/C pulley and shut the car down instantly. It didn't start again until I had moved the wire away from the pulley. I would also check your alternator power wire, since it could also cause this (same circuit).

There was a link in the other forum that according to the poster they recommend changing the PCM before the alternator. Here's the link I found, but for some reason the actual link with the info won't open on this computer (big brother) so... Here's something at least.

https://www.corvetteforum.com/forums...ode-p1637.html

VerdeZ28

I covered them as best I could with electrical tape. I feel that if it were an issue with this wiring it would be more intermittent and random. This thing shuts off like clockwork around 120-160 and if i could get it started again it will run fine until it cools down again and i start it again.

VerdeZ28

Yeah I saw this too but I wanted to look into it a bit further before throwing a new PCM at it. Alternator circuit looks good with some simple resistance testing.

Old Geezer

iTrader: (3)

Bout time to data log it, and capture the event....

ChopperDoc

Any progress on this? Do you have a log of this happening? That would be very helpful. I'm looking at the stock tune for my 98 Camaro right now, and LTFT enable is set at 149*. However, CL enable is set at 93*, so this is probably not the issue. You should already be in CL by the time you hit 150. Could be something going on with your LTFT's, which leads back to the PCM issue.

PCM's aren't too expensive for our cars these days though. I picked my 0411 up for $250 iirc from MRK motorsprots. He works pretty slow though, just so you know. But, in his defense, the PCM came with all the segments I needed to run my 4l80, and the one to make my fuel gauge work. Mine was a swap though, and required repining the entire harness, well, except 4 wires. 1 on the red connector, and 3 on the blue. The rest moved somewhere else. So that was fun. And good for the old back.

Also keep in mind the temp on the gauge and the temp the PCM and scanner sees are off fairly often. The gauge seems less accurate in most of these cases.

VerdeZ28

So I was able to datalog the event. I started with the car completely cold and in total it shut off 4 times, hence the separate datalogs. After restarting it for the 5th time it seemed to have normalized and it ran fine. Each datalog is titled for the corresponding shut off time it recorded. I personally cannot see anything that stands out. Also I should add the car is not stock, it has an aftermarket cam and heads(installed in 2014) but it was professionally tuned and it has run perfectly until recently so I don't think its the tune but I could upload that as well.

VerdeZ28

Is it possible to tell if the PCM is going bad from the datalogs?

ChopperDoc

I'm trying to figure that out right now. So far the only odd things I see in the logs are, at least on the last one, your O2's stop switching for extended periods with no real changes on your TPS. Not a big deal, might even be normal for your car, but I am used to seeing them constantly switch until you mash the gas.

The really weird thing I see, but it could also be your update rate as it's not capturing the data fast enough (which is probably the case) is the firing order. It is very strange. Normal LS firing order is 18726543. For some reason I focused on that probably longer than I should have, wrote some things down... This is what I found: 472514 72614 727261 etc. It seems completely random. Again, it's probably just the update rate and not seeing the actual firing happen fast enough in the scanner. But if we are considering a bad PCM here, then maybe it is missing a cylinder here or there. That might be tough to notice if the PCM is still firing at the right time, and just neglecting a cylinder here or there.

This is a very interesting problem though. I can almost see your frustration in the log. The last one I saw some throttle. This is a weird one. It actually goes into CL and then it still dies anyway. So I do not think it's your tune, or the CL transition. In either case, I would think PCM though. Are you getting any other codes now?

The only other thing I can think of here that would cause it to just die would be the crank position sensor. If I am right about the firing order being all crazy (I don't usually log it honestly, so I can't verify), then the CKP sensor could be an issue. Maybe it's getting hot or something, or a wire is rubbing somewhere. I'm just thinking out loud though. If it was my car (which I couldn't start at first because of said sensor) then I'd be hoping it was that too.

Unfortunately, my gut is leaning towards it being the PCM.

ChopperDoc

I just thought of something else. I'm really rooting for you not to have to change the PCM. Try logging the voltage to the PCM and see what happens to it when it dies. With the ignition on, you should have a constant 12v power source to the PCM (something like that), and if for some reason the power suddenly gets cut off, perhaps it is a relay going bad, or something simple like that. Or a wire, or a lot of things.

Add some more info to your logs. Try logging PCM voltage, fuel pump voltage, and anything else you can think of on that. There may be a way to at least confirm with the scanner if you have a separate electrical problem. The scanner can be a wonderful tool for troubleshooting electrical.

And by the way, another vote for the CKP sensor is that when my car refused to start (fired only on cylinders 1,3,5, and 2) I never once got a code for it. And I ripped that car apart trying to figure that one out, building new ignition harnesses and everything. What a simple fix that was in the end. I had used a cheaper knock-off ICT billet sensor. Should have spent the extra three bucks for the AC Delco in the first place. But hey, you live and you learn.

VerdeZ28

I don't think its the Crank position sensor since I just replaced it hoping it would fix this. It didn't make any difference. I think if it were the crank sensor or wiring to it it would not run at all.

Ill try data logging PCM voltage and Fuel Voltage too and anything else i can think of. I wanna add that I got code P0335 while doing all of this but that could be caused by the cranking trying to get it to start, or so I understand that to be the case. Also I never did do a crank relearn when i put in the new sensor, can hptuners do this or do I need the tech2.

Thanks again

VerdeZ28

I wanted to add that the firing order thing is due to the logger not being fast enough to explicitly get the correct order. Not sure why this parameter exists at all. I added it to see if it would reveal anything having to do with the crank sensor, but it was kinda pointless since it isnt fast enough.

ChopperDoc

I figured that was the case with the firing order. Yes you can do a crank relearn with the scanner. It's under the special functions tab. I doubt it will do much, since this really seems like a power issue. It's like you're tuning the key off. It's either the PCM is losing power, or it's getting power and then suddenly cuts it to the ignition, internally. The fuel pump could cause it too, in a similar way. It just suddenly dies. I'm just trying to think of the cheaper things first. A relay can also behave like this, all it needs is a momentary interruption to kill the ignition. I'd try swapping them around to check them. It's quick and free to try.

And if you have a multimeter I'd be shooting wires related to the ignition and checking for issues there, all the way to the key. This really seems like a electrical problem, or the PCM. I would rule out the wiring before dropping in a new pcm though.

ChopperDoc

With that code it might actually need a crank relearn. Forgot to add that. I would still be checking all associated wires. Those ones are down by the exhaust and can heat up pretty good. Heat can cause electrical problems on old wires if it gets hot enough. I should also add, that I had a brand new sensor down there that was bad out of the box. Try the crank relearn and see if the code comes back. If it does, check the wires to the sensor. That code shouldn't come on because of cranking. Open up the harness, or just splice in new wires straight from the PCM to the sensor. That could definitely be your problem. The sensor is probably good since the car starts and runs. But when it gets hot, as in heat soaks that harness down there, or plug, it suddenly dies. Seems logical to me.

VerdeZ28

I datalogged again and tried to add the parameters you said before. I couldn't add fuel voltage but I was able to add control module voltage. It only died once and like before would not start again until a minute passed. But after it started it ran fine for the most part. This is the most frustrating part. It only happens as the car is warming up, but once its fully hot its fine. I would be able to take it out and drive anywhere and not have an issue until i shut it off and let it cool down. Weird.

Also I have seen some videos on doing the crank relearn and when I try it it seems to fail the relearn. I am going to try it again though but I am concerned that only the Tech2 can do it for this car. Also I have a much older version of hptuners so I am going to try to update it and see if there are more parameters i can add and ill actually take it out for a drive and see if anything pops up. I uploaded the tune itself this time, not sure if you could take a look at that and see anything that pops out but like you said I don't think the problem is there.

thanks again for your help.

VerdeZ28

I wanted to add that I put a fuel pressure gauge on the rail and it was at 58psi the whole time while running as far as i can tell.

ChopperDoc

It's not letting me download the files... This site messes up sometimes. This is the second time in the last few weeks this has happened.

I'm not sure if you need the tech2 to do a relearn on your car or not. I don't see why hp tuners would not be able to do it. If that is the case, then perhaps it's once again leaning towards the PCM being bad. Did the voltage do anything out of the ordinary? It should have remained stable, running or not. This is a very strange problem. I am hoping to prove one way or the other. I still think something might be up with the wiring, since when that code comes up, it is usually a wire. I just don't want to outright say it's the PCM and have it be something simple like a bad relay or wire.

ChopperDoc

Well then it's not the fuel pump...

VerdeZ28

So I logged it again today and this time i saw some interesting behavior. ultimately the pcm is somehow losing communication with the crank position sensor somehow. I logged it for a long time and did not reset the logging between the times it shut off while warming up. You can see around the 6:30 mark that I am giving throttle input while the engine was off. I did this to verify that it was still logging and communicating with the pcm even though it shut off. The interesting thing is that when i first cranked it you see rpm read out even while its cranking. But after the first shut off I cranked it for a while and you dont see any rpm. Hence why i think somehow its loosing the crank signal. I marked every time I cranked by pressing the throttle a bit before just to have some marker on the log.

Anyway it shut off 2 times and on the last restart i decided to take it out. You will see like I said before, once its fully warmed up it runs fine. I don't think it would run as well as it does if the wiring of the crank sensor was bad or if the sensor is bad itself, so what would cause the PCM to loose signal?