jmalto

This is scary because I just bought a used 08 Z and the dealer I bought it from (non-chevy) said it was stock with the remainder warranty based on their inspection. My car just had the check engine light and flash update for the cat issue that the OP did. While it was there I asked them to verify the tune was stock and told it was.

Do dealers offer a GM certification inspection check on used cars that I could pay for to verify the car truly is "stock" so I have something documented?

3LZZ06

This would have never crossed my mind for such a low mileage Z (1500 miles)

Word to the wise for potetial used Z buyers "Check the PCM for a stock tune before you buy it"

Man...what's next? ....

mirage2991

The thing is, if the ECM was reflashed for an update by GM, then the none stock program has been over-written and no trace of it is left!
I'm thinking they just don't know how to check it correctly, despite the clear instructions stating that if it doesn't match they have to call GM to find out what the preceding, pre GM reflash CVN number was. and I believe it state only the last 3 digit have to match isn't it?

RichieRichZ06

WOW, just like Jason said this has been discussed, but I never thought it would actually come up. I agree with the rest that you need to go after the dealer that sold it. Although they probably had no way to know it was tuned at some point. After the person flashed it back to stock, the CVN's would match still, but the programming history would be off.

We just ran into this with a Duramax in our shop. It appeared to us to have all the correct matching CVN's, but when we sent the Tech II screen shot off to GM for verification, the programming history did not match. All of the CVN info was correct, but there was obviously over written tunes that were flashed back to stock. We as the dealer had no way to verify, but GM did.

This should at least put to rest the theory that a tuned PCM can be flashed back to stock and not be detectable to GM. If anything, it proves that is a load of crap, just like many of us have been sayng for months.

jmalto

Richie - What was the end result, was the warranty denied?

RichieRichZ06

Due to the PCM being "heavily modified", the Powertrain Quality Center denied the claim and stated "the repair is now the customers responsibility." It is now at the machine shop repairing the damaged cylinder and replacing the broken parts. It popped a 1/2" hole in #5 piston and was about to do the same on #2. Unfortunately a new Duramax motor is about $9,500 so repairing it was much more feasable.

jmalto

Wow, I hate to say it but I am regretting buying my Z now. I understand if you modify it and it blows you have nothing to complain about, but the fact I can't even find out if my Z has a stock tune from a dealer has me

RichieRichZ06

We could tell you if it had been programmed, but it would take us sending the screen shot to GM..........Do you really want to do that or just cross that bridge when the need arises.

There are obviously ways around it and they are discussed on here. I can not or will not validate those methods of cheating GM though.

RICH

Joe_Planet

The dealer doesnt want to do the work. Plain and simple.

You had the car in there in Dec for a software update which would have overwritten a non stock tune even if it was present. So GMs claim is null and void. Get the proper documentation proving that your computer was reflashed with a stock tune and the failure happening after that time and quit taking **** from these idiots!

jmalto

Actually yes, I would like to know because I am keeping the car stock to preserve the warranty. If the warranty is shot, then I would just go ahead and mod the car and roll the dice or sell the car for a loss (as stupid as this may sound.)

Painrace

GREAT comment! An HONEST man! We need more of them in this world!

Jim

RichieRichZ06

Any dealer should be able to email the screen shot to GM and get an answer for you. It does not sound stupid to me at all. I guess I would also want to know if the car had a tune and what I would be responsible for in the future.

jmalto

Richie - You have been very helpful with your responses and with all the Z's blowing up this week it has me a little worried since I just got the car last week.

Can you tell me exactly what I would need to ask my dealership to do in order to get verification from GM that the tune has not been altered? I do not want to go down the avenue of trying to fool GM, I just want clarification that my warranty is good which is why I paid more for an 08 vs an 06.

mirage2991

I'm not so sure about the programing history deal. I know the Duramax ECM have alot more feature that protects or record the integrity but, I've not heard this on other ECM...I'll do some research. I know our ECM have no re-flash counters, so my guess is that your ECM was reflashed with a stock GM tune that was not the one out of the car, hence the number no lining up -a speculation for now-

KMK454

Great. Sorry to hear your troubles

I'm a day or two away from getting a GM certified w/ extended warranty and now this pops up on a used car... a mystery tune from before. I've been down the road before with a European car that lost its motor and had an aftermarket tune on it.

How can the dealership verify a stock, never-been-flashed tune?

EDIT - If you bought it with 1500 miles on it at a GM DEALERSHIP, shouldn't their 117 point inspection figure this out? Otherwise they gave you a false certification, especially if you can prove the tune happened PRIOR to your purchase of the car!

RichieRichZ06

Thanks.

You would simply have to go to the dealer and let them take the screen shot from the module ID info in the PCM. They can at least pull up the correct CVN lists for your VIN online and see if they match. If they do, that is a good sign, but it should be verified with GM Technical Assist Center or PQC.

Luweegy

I would contact the original owner and find out what if anything he had done to the car to verify that it was altered before you bought it. We had a 07 Duramax at the dealer for a trans problem.They said it had been tuned.I've serviced this truck since new for a friend of mine. It is bone stock.Come to find out it had been recalibrated in Denver for a DPF problem by a GM dealer.They took care of it under warrenty finally.

VetteVinnie

Just curious, but what is the build date on your car? Was it prior to 8/07?

LFZ

good point. Wow, I can't believe these stories...amazing. Sorry to hear about your troubles. I still can't believe these motors aren't holding up, even with a tune....did GM make these engines to be built to the very limit from the factory and any power adders after that are set up for catastrophic failure?

RichieRichZ06

The D-max really has a lot of records built into its PCM and TCM. I learned the TCM (trans control module) will store a calculated torque value based on what TQ it sees from the engine. It is stored not only as current info, but also the highest recorded reading. Since then I have checked a couple trucks I know to be tuned and have seen readings up to 968 LBFT through the Allison trans.

The PCM in the truck will also store history of emission re-generations, module programming history and a list of CVN's. There is even more it can do, but I can't get into it on here.

Just for fun, I went and checked my tune compared to he factory list of CVN's for my VIN and it does not match. I re-flashed mine to stock with HP tuners and it still showed a difference from what is online. After flashing it using a Tech II, the CVN's finally matched up, but the order they're listed in changed, probably showing big brother that at some point the programming had been re-written.

Of course none of this matters for me because my car is out of warranty and the repair would be on me if it blew up.

RICH