Aftermarket Modifications and Your GM Warranty

Volume 2 Issue 4 - Extra

Follow Up

Last issue, Joel Paynton wrote about aftermarket power modifications on the Duramax diesel and their potential affects on your GM warranty. Shortly after, on August 4, 2009, GM posted Bulletin #08-06-04-006D which contained this statement:

Important: In order to process ANY driveability/engine/transmission/drivetrain WARRANTY CLAIM, you MUST photograph the required Tech 2® screen information BEFORE servicing or removing any engine/transmission/drivetrain components from the vehicle.

Duramax modifications and GM warranty follow up

This had broad implications, requiring a technician to do all the groundwork to ensure there is no power program in the truck before doing any powertrain warranty work. It could be interpreted to mean that even minor and completely unrelated powertrain issues, for example, leaky seals, an electrical failure, a failed sensor and so on, would obligate the technician to investigate and document if there is a power program in the ECM. GM seemed to be launching an all-out campaign to find and stamp out anyone running aftermarket calibrations in their ECM.


The documentation procedure includes getting a photograph of the CVNs as listed by the Tech II scan tool, printing them out and stapling them to the hard copy of the work order. It also includes comparing all CVNs with the GM listing to determine if there is an aftermarket program in the ECM. GM also had to be informed by email whenever an aftermarket calibration was discovered. This whole process seemed like an extensive paper chase to endure for minor and typical repairs. It also takes time – who would pay the technician and the dealer to get this done with every Duramax that came into the shop? A good question. Even more confusing, several important steps referred to in the bulletin were completely missing. What prompted GM to attempt this kind of logistical nightmare – confusing to technicians and dealers, with the apparent idea to clamp down on any owners with power programs?

We can only speculate. Note this excerpt from my article:

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Comments (2)add comment

campbelltm said:

2003 6.6 tapping/clicking noise
Hi Joel, i am a gm gas drivability tech, now instructor, i wanted a diesle really bad, i was able to purchase a high mileage, 300.000 for a price i could afford, even if i had to repair an engine, vehicle performs great, 24 mpg, no oil consuption, and a very smooth ride. Not being a diesle tech, i hear a noise that i would describe as an upper end tapping/ clicking, louder on acceleration, and louder colder. Should i be concerned, Vehicle had regular service, every 4000 miles, and just had new injectors.
April 11, 2011
Votes: +0

jpaynton said:

Hi, what you are describing is sounds quite typical for an early Duramax. If you don't have smoke, you should be just fine. If it's the same noise I'm thinking of, you could describe it as a loud "pinging" noise if it were a gasoline engine. This noise is diesel combustion 'knock' which is typical.
April 15, 2011
Votes: +0

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Joel Paynton is an award-winning GM technician who specializes in Duramax fuel systems. He also does custom programming for any GM powertrain. Visit him on the web at


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