tached_out

Here is a picture of my 2008 GMC W3500 just after I finished building the deck and got it on the road. It was sold by GM but it's the exact same as an Isuzu NPR. It has a Chevrolet 6.0L gas engine and 4L80E automatic transmission.



I have absolutely loved this truck, until now.

It started last spring when the transmission control module failed. DTC U0101 (lost communication with TCM). I borrowed a friend's scan tool and learned this.

Isuzu sent a tech to my place as it was cheaper than the hundred mile tow and ferry fare to the closest dealer. The guy was very pleasant. I'm sure he liked getting out of the shop for a day. I gave him coffee and we actually worked on the truck together. We installed a new TCM and flashed it to the truck. This was a ten minute job. While he had the Isuzu diagnostic tool and laptop connected to my truck he also "updated" my ECM. We went for a quick test drive to ensure the problem was fixed and that was that. Or so I thought.

Since then I have experienced a tremendous loss of power and fuel economy. I have spent the entire summer getting no better than 9 mpg when I used to get almost 15. I have to use a lower gear on every hill that I used to be able to fly over. I have complained to Isuzu until I'm blue in the face and they keep telling me there is nothing wrong with my truck. They sent the guy back two times and verified that the computer was working perfectly. Apparently I'm imagining things or I must be driving differently. I should also mention that my exhaust pipe is now black and wet inside and the entire exhaust system has turned multiple shades of purple.

So I borrowed my friend's scan tool again. Here are two observations I made while viewing the live data during my test drive.

First, I'm getting no more than 70% throttle position, even with my foot to the floor. (It's drive by wire)
Second, At all cruising rpms I have very low spark advance values all the way down to 0 spark advance under full throttle. I think I found my problem.

I have since discovered that Isuzu had a problem with these trucks eating transmissions so they developed an ECM "update" that reduces engine torque. They accomplish this by limiting the throttle opening and retarding the spark.

I couldn't care less about the problems they have had with the tucks eating transmissions. Mine is fine and my truck is off warranty. I don't think they had any right to change anything.

Isuzu will no longer talk to me and here is the ripper. There is no way the ECM can be re-flashed to it's original state.

I have looked into aftermarket programing products but my truck is not supported by any of their software. I really like the looks of HP Tuner's VCM suite. I emailed them and they say that I, "SHOULD" be able to tune right away. I have to look into this with them a little further.

Until then, I'm screwed and I'm not very happy about it. Any advice at his point will be greatly appreciated.

By the way I'm not a dummy when it comes to mechanicals, I have just never gotten into an ECM before.

Thanks guys. Let me have it.

turboal1

find a tuner in your area and have him do a street tune on your truck

Kevin Blown 95 TA

I didn't even have to read half of your post before I figured out what they did to your truck (de-tuned it). I think that is pathetic on their part.

CattleAc

iTrader: (7)

It will cost you a little bit...but I'd get in touch with any number of tuners that are out there, and have them send you a "reflashed" ecm. You can send yours back for the core whenever you get it swapped out...that way your truck will never be down...


(I've used Jess at Wait4Me before with good luck)

tfi racing

iTrader: (2)

If it were only that easy,as the crow flies only a few hours out of Seattle(and not far from where I am),but several expensive ferry rides away...To the OP,post some pics and part numbers of the PCM,I'm sure someone here has some good advice,you likely have to buck up for HP Tuners or EfiLive and take matters into your own hands.There should be a competent tuner or two in the lower mainland,if there are any I would like to know who they are as well.

ctd

iTrader: (1)

If you go with HP Tuners it is pretty straight forward to upload & download tune files. It will most likely run better than it ever did. I'm taking a few days off around Ucluelet next week & I will have my laptop with me, where is Half Moon Bay?

ctd

iTrader: (1)

Just mapped your location, long ways away. None the less if you decide to go with HP Tuners I would be more than happy to help you get it sorted out.

ramairetransam

iTrader: (18)

get in touch with frost or another person that will do a mail order tune .

Mike@Diablosport

iTrader: (2)

Just be glad it is a 6.0 GM motor and not the junk 4 cyl diesel

Carnutsx2

Can you just copy a old stock tune or a mail order tune with a HP tuner?

murphinator

iTrader: (2)

how about a pcm out of a wrecked one ? hoping of course it didn't get that great update...

Rise of the Phoenix

iTrader: (27)

At least the problem is fixable with a new tune. Could be a hell of a lot worse.

Big Al

iTrader: (1)

Some of the 8.1L pickups won't go full throttle unless you press the tow/haul button. They are limited to about 75% throttle.

From what you said about the exhaust system turning purple, I'd look for something plugged up. CAT or muffler? You can pull an O2 sensor and see what kind of back pressure there is.

Al

y2k_ta

iTrader: (80)

As someone else mentioned, maybe you could get a used ecm?

Sorry about your circumstances, but I must say I do like your wood bed!

tached_out

Guys, I'm sorry I started this thread and then disappeared. I decided to ignore my truck problems for a while and just concentrate on by business and some other things going on in my life. I'm happy that's going fine but now I really have to turn my attention to this truck, otherwise I'm going to end up slashing my wrists.

Thank you for your advice so far and especially ctd for your offer to help.

Right now I've got both time and some money. I'm ready to pull the pin on something I just have to figure out what. Armed with what I know up to now, it looks like I have four options.

1- Buy HP Tuners VCM Suite and take on a (steep for me) learning curve. I'm not afraid of this, but their answer to my original question, "is my truck supported?'' worries me. They say I "SHOULD be able to tune right away".

2- Buy an MSD 6012 controller and a 88862 EFI harness so I can retain everything else that's factory. I know this won't fix my throttle position issue, but I'll get a spark curve that burns the mixture in the engine instead of in the exhaust system. I can initially use one of their chips to get going, then learn how to create a custom curve of my own.

3- Send my ECU away to get a tune put on it. I like this idea. I actually have the original ECU that the truck came with. I'm hoping I can send it away and avoid any down time. This is the one that got Isuzu's "torque limiting update". They replaced it with a brand new one, but it ended up with the same crap program on it. So I have the original one sitting here on my desk.

4- Lastly I can drive anywhere in the lower mainland of BC and get someone to give me a new tune. Isuzu can't or won't do this. I already asked, but they want to spend a ton of my money trying to diagnose the problem. I already know the problem, they gave me a crap tune. Plus I don't think their IDSS (same as a GM Tech-2) even has the factory tune on it.

I'm really motivated to get going on this. I'm really worried that I'm shortening the service life of this engine by driving with such low spark values. I'm getting red hot exhaust. It's a good thing GM put inconel valves in this thing.

Please give me your best advice. Thanks again.

scout2000

Glad to see you are back.

Although I have no directed experience with your vehicle type, I though you have a very interesting thread, at least from my perspective. I am sure all of this is a PITA from yours.

I wanted to throw a couple of additional options to your above post, specifically on your item #3.

Two more additional items you might consider along this theme, is to:

* go grab a non-modified ECU from a junk yard truck that still has the old setup on it.

* Acquire another ECU (either new or used), and send that one off for a tune. Worse case, you would have a spare to send back and forth to the tuners, and you would still have your original. What ever happens with the new one, at least things won't get any worse.

I did an LS swap into an old International Harvester that I have plans of turning into a daily driver. As such, I have a spare put aside for any mechanical issue that might hit me, where the spare part isn't something I could get off the shelf at O'Reilly/NAPA/misc auto parts store.

I acquired a 2nd, identical PCM for my truck from the junk yard, and then sent them both off to the tuner during the time my drive-train swap was in progress.

Or, you could keep your current ECU in its current configuration for any time you might need to have your truck serviced by Isuzu, and run a new/tuned ECU the rest of the time.

Food for though. Always have a plan B readily available.

LSX Power Tuning

iTrader: (4)

Can you post a picture of the pcm where I can see the hardware and service numbers? If you can get me a pic I can tell you if can tune it on my bench harness.

tached_out

I hope you can help. Thank you.

tached_out

I'm sorry. I have no idea why my pictures keep ending up upside-down. Here's another try.

tached_out

I rotated it and sent it again and it's still upside-down. I'll quit now.

I hope you don't think I totally useless. I've been having this problem with pictures since I installed Yosemite on my Mac.