Start Up Cooling Fan Noise - Updated EV Cooling Fan and PCM Calibration - keywords accelerate cold delay engine flare intermittent low power roar shift slip

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

On rare occasions, a roar noise, lack of power, and/or delayed transmission shifts may be experienced on acceleration, shortly after cold starting the engine. Some customers may mistake this as a transmission slip concern. Upon inspection, no DTCs will be stored in the PCM.

If the SI diagnosis do not isolate a cause for this concern, determine if bulletin 04-01-38-019A was ever performed on the vehicle to address an AC performance issue. If this bulletin has not been performed, recalibrate the PCM with the latest TIS calibrations and replace the EV cooling fan clutch using the part number listed in the GMSPO parts catalog. At this time, all available PCM calibrations and EV cooling fan clutches may improve this concern on the models above.

If this concern still exists after installing the updated EV fan clutch and PCM calibrations described above and in 04-01-38-019A, test drive the vehicle for at least 4 minutes with the engine RPM at 1,800 RPM or greater to determine if a P0495 sets. If no DTCs set, this is most likely a characteristic of the vehicle as described in Section 5 of the Owner's Manual and bulletin 06-06-02-003.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.