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GM blames after-market software for Duramax problems

General Motors is telling dealerships how to look for after-market modifications to control software that voids warranties and can cause damage to Duramax diesel engine components.

In a Technical Service Bulletin (TSB), General Motors sent updated information to dealership service departments on identifying non-GM engine control module (ECM) calibrations. The TSB also extends the procedures to cover any Duramax-equipped vehicles built for model year 2013.

The bulletin outlines software identification and hardware detection procedures during power-up. It recommends that any "hard part failure" that is observed on internal engine, transmission, transfer case, rear axle assembly, or exhaust after-treatment system (currently under warranty) be subject to the procedures to find after-market, non-GM modifications to the Duramax vehicle. Any such after-market changes automatically void the GM warranty on the Duramax powertrain.

GM is reporting an increasing number of engine, transmission, diesel oxidation catalyst, and exhaust particulate filter failures in vehicles that have been retrofitted with unauthorized engine and/or transmission software calibration. These software changes are often a likely culprit in failures, but many GM service departments do not actively search for them or do not have proper procedures in place for doing so. Hence TSB 08-06-04-006J.

Several after-market suppliers offer kits to modify the software calibrations in the powertrains of several production vehicles, including the Duramax. Normally, these kits are sold with disclaimers that they may void manufacturer's warranties or are for off-highway use only, the market for the kits is generally assumed to be vehicles used on public highways.