How to fix P2138 Reduced Power on GM vehicles
GM has issued a technical service bulletin # 07-06-04-019D to address a P2138 Reduced Power issue. The P2138 trouble code may be stored in the computer along with a check engine light. The P2138 Reduced Power bulletin applies to the following vehicles:
# 07-06-04-019D has been updated to #07-06-04-019E and includes more vehicles and more troubleshooting, Find the updated bulletin here
2005-2011 GM Passenger Cars and Light Duty Trucks (Including Saturn)
2005-2009 HUMMER H2
2006-2010 HUMMER H3
2005-2009 Saab 9-7X
The P2128 trouble code refers to Accelerator Pedal Position (APP) Sensor 1-2 Correlation.
Do NOT assume you have a bad accelerator pedal sensor. GM says the condition is caused by water leaking into the body harness connector that carries the APP signal to the PCM. The water changes the voltage readings from the APP.
However, this code can also be generated by the installation of aftermarket equipment that is tapped into the wrong wire (radio, remote starter, radar detector, etc).
Locate the body harness connector, located in and around the left hand kick panel area or inside the IP (consult a shop manual for location). Water can leak into the connector from clogged sunroof drains, A-pillar leaks, or windshield or cowling leaks. If you find water in the connector, locate the source of the leak. Then dry out the connector, apply dielectric grease and reseat the connector.
Then clear the trouble codes and check for proper operation.
©, 2015 Rick Muscoplat
Posted on by Rick Muscoplat
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