GMC Sierra owners have reported 3 problems related to automatic transmission control module (under the power train category). The most recently reported issues are listed below.
On July 29, 2015, while driving at approximately 45 mph, the vehicle suddenly downshifted itself into first gear causing the vehicle to slow down suddenly with no notice. I was able to get the vehicle off the road and into a gas station. After the fact the check engine light was illuminated. The vehicle was towed to the dealership. I was told the tcm (transmission control module) needed replacing and that there is a known issue with this year truck. This is a very dangerous situation to have your vehicle suddenly slow down while driving at speed. If gm knows that the part is faulty why is there not a recall? will it take multiple deaths before gm takes responsibility?.
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all problems of the 2011 GMC Sierra
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Intermittent surges, loss of power while in motion, transmission, lack of acceleration. At purchase, the check engine light came on three times before leaving the dealership lot. Dealer advised that the dealer installed remote starter or alarm system was interfering with fault sensor and was not a problem. However the lost power while driving, intermittent surges and stall outs at freeway speed/85 mph still existed. On one occasion consumer was almost in an accident when the transmission clanged between gears and there was poor acceleration. Consumer had to shift into 4 wheel drive or manually downshift, or turn the engine off then on again. Dealer replaced pcm module, fuel pressure regulator and gaskets, fuel pump assembly. However problem still exist. Dealership agreed to hold the vehicle for further investigation. Further investigation revealed that the wires from the dealer installed accessories such as the alarm system and remote starter or anti-thief system, and factory wire from pcm/vcm to the transmission be replaced. Dealer replaced all ignition wiring, wiring from the pcm/vcm to the transmission and replaced the control valve body that regulates the cruise control. Consumer has been without vehicle for more than 21 days and will seek a replacement vehicle if wiring repairs does not remedy the problem(s).
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all problems of the 2002 GMC Sierra
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The vehicle surged, the remote starter interfered with the fault sensor which caused the engine light to illuminate. The vehicle lost power while driving, and stalled, the fuel pump was replaced, however the problems continued. . The transmission changed between gears, and the dealer changed the pcm. The problem was discovered to be incorrect wiring which was routed wrong within the ignition which caused the problems.