Uneven or Fluctuating Engine Idle (Reprogram PCM) - keywords 3.8 intermittent L26 rough RPM surge

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

Some customers may comment about an uneven engine idle or an idle speed that fluctuates up and down slightly. This idle condition does not result in a stall.

Reprogram the Powertrain Control Module (PCM) with a new calibration.

The new calibrations will be available with TIS version 3.5 which is scheduled for release to dealers on 3/19/05. As always, make sure your Tech 2® is updated with the latest software version

Important: The calibrations listed below only contain the changes necessary to correct the described condition. They do NOT contain changes or "fixes" for any other condition.

Important: There are two new calibrations to choose from. The calibrations are based on the type of fuel tank installed in the vehicle. Vehicles that have had Technical Service Bulletin # 04-06-04-066 performed, require a calibration for a "baffled" fuel tank. In addition some late production 2004 models may have been built with the "baffled" tank. All others should have a "non-baffled" tank.

To determine which calibration is correct for the vehicle, obtain the Part Number of the calibration currently in the PCM using a Tech 2®. Compare that Part Number to that listed below and reprogram the PCM with the corresponding new calibration.

Current PCM Calibration 12592106

New PCM Calibration 12600366 (for vehicles with BAFFLED fuel tank)

Calibrations other than Current PCM Calibration that listed above use new calibration 12600365 (for vehicles with NON-baffled fuel tank)

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation / Description

Labor Time

J6354 - PCM Reprogramming

Use Published Labor Time

Please follow this diagnosis 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.

(2004 Pontiac Grand Prix)