Technical Service Bulletins

Identifying non-GM engine and transmission calibrations

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Identifying non-GM engine and transmission calibrations

This GM TSB relates to 2006-2009 GM passenger cars and light trucks and 2006-2009 Hummer H2 & H3 (excluding Saab 9-7X). General Motors is identifying an increasing number of engine, transmission and catalytic converter part failures that are the result of non-GM (aftermarket) engine and transmission control calibrations being used.

When alteration to the GM-released engine or transmission control calibrations occurs, it subjects powertrain and driveline components (engine, transmission, transfer case, driveshaft and rear axle) to stresses that were not tested by General Motors. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy to cancel any remaining warranty coverage to the powertrain and driveline components whenever the presence of a non-GM calibration is confirmed, even if the non-GM control module calibration is subsequently removed.

Warranty coverage is based on the equipment and calibrations that were released on the vehicle at time of sale, or subsequently updated by GM.  That’s because GM testing and validation matches the calibration to a host of criteria that is essential to assure reliability, durability and emissions performance over the life of the warranty coverage and beyond. Stresses resulting from calibrations different than those tested and released by GM can damage or weaken components, leading to poor performance and or shortened life.

Additionally, non-GM issued engine control modifications often do not meet the same emissions performance standards as GM issued calibrations. Depending on state statutes, individuals who install engine control module calibrations that put the vehicle outside the parameters of emissions certification standards may be subject to fines and/or penalties.

This GM bulletin outlines a procedure to identify the presence of non-GM calibrations. GM recommends performing this check whenever a hard part failure is seen on internal engine or transmission components, or before and engine assembly or transmission assembly is being replaced under warranty. It is also recommended that the engine calibration verification procedure be performed whenever diagnostics indicate that catalytic converter replacement is indicated.

Beginning on May 18, 2009, the PQC requires a picture of the engine calibration verification screen before authorizing any V8 gas powered engine replacement.

If a non-GM calibration is found and verification has taken place through GM, the remaining powertrain and driveline warranty will be cancelled and notated in GMVIS and the dealership will be notified.

1. Plug in the Tech 2.

2. Go to diagnostics and build the vehicle.

3. Select “Powertrain.”

4. Select “Engine.”

5. Select “Engine Control Module” or “PCM.”

6. Select “Module ID information” or “I/M Information System” if module ID information selection is not available.

17. If “I/M Information System” was selected, it may be necessary to select “Vehicle Information” in order to display the calibration information.

8. Take a CLEAR digital picture of the Tech 2 screen showing the engine calibration verification information as shown in the above example.

9. E-mail the snapshot picture to In the subject line of the e-mail, include the phrase “V8 Cal” as well as the complete VIN and Dealer BAC. In the body of the e-mail, include the VIN, mileage, R.O. number and BAC.

10. Allow two hours for the PQC to verify the calibrations and set up the case details.

11. You may call the PQC two hours after submitting the e-mail for authorization to replace the assembly. This will provide them time to receive, review and set up a case on the request. Please be prepared to provide all the usual documentation that is normally required when requesting an assembly authorization from the PQC.

If the CVN information is displayed as “N/A,” it will be necessary to contact the TCSC (1-800-828-6860) to obtain the CVN information.

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