ECM Commanded Reduced Engine Power

Under certain conditions the ECM 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 ECM will illuminate the reduced engine power lamp on the instrument panel cluster, however 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 to determine the reason for the reduced engine power.

Verify or inspect for the following:

• Vehicle being driven inappropriately. Towing heavy loads up an incline for an extended period of time or operating the vehicle at sustained, excessively high engine speeds 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.
• If the vehicle is 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.
• A cooling system condition which may cause the engine coolant to overheat. Refer to Hybrid/EV Cooling System Description and Operation to verify correct operation of the cooling system.
• High pressure fuel system condition. Refer to Fuel System Diagnosis and Fuel System Description to verify high pressure fuel system operation.
• Intake air temperature too high. Engine running, observe the scan tool IAT Sensor parameter. The readings should be between -40°C and +149°C (-40°F and +300°F). Refer to DTC P0112, P0113 or P0114 for additional information
• Fuel temperature too high.
• A hybrid/EV propulsion system malfunction. Inspect for the following conditions:
  • Hybrid/EV battery pack charge too low. Review the scan tool Hybrid/EV Battery Pack Charge Remaining parameter for a Battery Power Low condition.
  • Drive motor or inverter temperature too high.
  • Engine powered Hybrid/EV battery charging unavailable. The Internal combustion engine (ICE) may be unable to charge the Hybrid/EV battery. Refer to the conditions listed below for a possible cause:
    • ICE has been run out of fuel. Review the scan tool Remaining Fuel in Tank parameter to verify that the engine has an adequate supply of fuel in the fuel tank.
    • Any ICE performance malfunction, such as an incorrectly operating ignition or fuel system. Review the appropriate scan tool parameters to help diagnose the condition.
    • A Hybrid/EV drive motor 1 (A) or 2 (B) malfunction.
    • An incorrectly operating transmission clutch.
  • An incorrectly operating transmission fluid pump. Inspect for the following conditions:
    • Incorrect transmission fluid level
    • Plugged or restricted transmission fluid coolers or pipes
  • For additional information, refer to Hybrid Modes of Operation Description .