ECM Commanded Reduced Engine Power

Under certain conditions the engine control module may limit engine power by reducing engine torque and, for some vehicles, fuel pressure as well. For most, but not all of the conditions, the engine control module will illuminate the reduced engine power lamp on the instrument cluster. If equipped with the driver information center feature, a reduced engine power message may be displayed as well. A DTC may not be set.

A repair may not be necessary. Observe the scan tool Reduced Engine Power History parameter or refer to K20 Engine Control Module: Scan Tool Information (LUV, LUW or LWE) to determine the reason for the reduced engine power event.

Verify or inspect for the following:

• Vehicle being operated at sustained high engine speeds or towing heavy loads up an incline for an extended period of time, which may cause the engine oil or coolant to overheat. Inspect the airflow passageways in front of the engine for obstructions and clear away any debris or foreign material that is found. If no obstructions are found, review approved driving habits with the customer. The customer may need to operate the vehicle at a higher engine speed to improve cooling system performance or, at a slower engine speed to reduce engine load.
• A cooling fan condition which may cause the ECM to reduce engine power. Refer to Cooling Fan Description and Operation (Diesel)Cooling Fan Description and Operation (Gas) and Cooling System Description and Operation (1.4L LUV) to verify correct operation of the cooling fan.
• If equipped with the OnStar® feature, reduced engine power may be due to OnStar® remote command. Verify the vehicle is not in the OnStar® initiated Stolen Vehicle Slowdown mode.
• High pressure fuel system condition. Refer to Fuel System Description and Fuel System Diagnosis  to verify high pressure fuel system operation.
• Turbocharger boost pressure out of range. Refer to DTC P0234 or P0299 .
• Intake air temperature out of range too high. Observe the scan tool IAT Sensor 1 and IAT Sensor 2 parameters. The readings should be within 9°C (16°F) of a each other. Refer to DTC P0096 or P0111 for more information.
• If equipped with automatic transmission, an incorrect learned brake pedal position (BPP) sensor. Verify the following actions have not occurred:
  • An engine control module (ECM) has been replaced
  • A BPP sensor has been replaced
  • A BPP sensor is misaligned or incorrectly installed

    If any of the above actions have occurred, the Brake Pedal Position Sensor Learn procedure must be performed.