Rick's Free Auto Repair Advice

Reduced Engine Power Message

Diagnose and fix a Reduced Engine Power message on a GM vehicle

GM has issued multiple services bulletins to address a Reduced Engine Power message with trouble codes on the vehicles listed below. The most common trouble codes that show up are P0106, P0651, and P2135, but the bulletin also lists these possible trouble codes
P0326 P0335 P0341 P060E P0561 P0651 P2120 P2122 P2123 P2125 P2127 P2128
P2135 P2138 U1863 U1886 U1899 U2105 U2106 U2107 U2143

Vehicles affected by the PIP4549B bulletin

2005-2010 Chevrolet Cobalt SS
2005-2010 Chevrolet Cobalt
2006-2010 Chevrolet HHR
2008-2010 Chevrolet HHR SS
2008-2010 Chevrolet Malibu
2007-2009 Pontiac G5
2008-2009 Pontiac G6
2005-2009 Pontiac Pursuit (Canada Only)
2007-2009 Saturn Aura
2005-2007 Saturn Ion
2004-2007 Saturn Ion Redline
2002-2009 Saturn Vue
With any of the following ECOTEC engines
2.0L Engine
2.2L Engine
2.4L Engine

Causes of reduced engine power message

P0106: Manifold Absolute Pressure (MAP) Sensor Performance
P0651: 5-Volt Reference 2 Circuit
DTC P2135: Throttle Position (TP) Sensor 1-2 Correlation
These codes may trick you into replacing the MAP or Accelerator pedal position sensor. Do NOT do that until you have read the rest of this bulletin. A common cause of the reduced power message and trouble codes P0106, P0651, and P2135 is a wire chaffing issue that shorts the reference voltage to ground and prevents the PCM from getting accurate sensor data from the MAP and accelerator pedal positon sensor.

Check for a wire rub through condition at the oil filter housing. Also, check for a wire rub through condition in the area of the canister purge solenoid attachment bracket. The routing forces the harness into the sharp edge of the bracket. GM also reports shorting to ground issues at the EVAP purge valve bracket on the side of the cylinder head as well.

GM Service bulletin 07-06-04-019E

GM has also issued this bulletin for ALL 2005-2015 GM passenger and light duty trucks for intermittent check engine light issues and a message that says REDUCED ENGINE POWER. You may also see a P2138 Accelerator pedal position (APP) Sensor 1-2 correlation trouble code.

GM says this issue can be caused by water leaking into the instrument panel body harness connector. This connector is located in or near the left hand kick panel or inside the instrument panel, depending on the year and model. If you find water, check for the source of the leak. That can be A-pillar seals, sunroof drain lines, or windshield cowling leaks.

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Posted on by Rick Muscoplat

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