Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to 2005-2015 GM passenger cars and light duty trucks.

  the passage

  2005-2015 GM Passenger Cars and Light Duty Trucks

• The malfunction indicator lamp comes on intermittently, with a message or indicator that displays Reduced Engine Power.

  the passage

  Some customers may comment on an intermittent malfunction indicator lamp (MIL) being Illuminated with a message or an indicator that displays Reduced Engine Power.

• A scan tool shows DTC P2138 (Accelerator Pedal Position (APP) Sensor 1-2 Correlation) set as current or in history.

  the passage

  The technician may observe on a scan tool DTC P2138 – Accelerator Pedal Position (APP) Sensor 1-2 Correlation set as Current or in History.

Possible causes

• Water may be getting into the instrument panel (IP) to body harness connector, which carries the APP sensor signals to the ECM/PCM.

  the passage

  This condition may be caused by water intrusion into the instrument panel (IP) to body harness connector, which carries the APP sensor signals to the ECM/PCM.

• The water causes a voltage difference between APP Sensor 1 and APP Sensor 2 that exceeds a predetermined value for longer than a calibrated time, which sets P2138.

  the passage

  This water intrusion results in a voltage difference between APP Sensor 1 and APP Sensor 2 that exceeds a predetermined value for more than a calibrated period of time, setting P2138.

Steps to confirm (in the document’s order)

1. Verify that aftermarket equipment is not electrically connected to the APP sensor signal or low reference circuits, or to any other ECM/PCM 5V reference or low reference circuit.

   the passage

   Verify that aftermarket equipment is not electrically connected to any of the APP sensor signal or low reference circuits or to any other ECM/PCM 5V reference or low reference circuits.

2. Locate the IP to body harness connector; it may be in and around the left hand kick panel area or inside the IP.

   the passage

   Locate the IP to body harness connector, which may be located in and around the left hand kick panel area or inside the IP.

3. Examples of potential water leak points are the A-pillar seals, the sunroof drain lines (if equipped) and the windshield/cowl sealing.

   the passage

   Some examples of potential water leaks are: A-pillar seals, sunroof drain lines (if equipped) and windshield/cowl sealing.

4. Inspect for a water leak in the area, using a water hose if necessary to find the source of the leak.

   the passage

   Inspect for a water leak in the area. If necessary use a water hose to determine the source of the leak.

5. Inspect the terminals of the IP to body harness connector for corrosion and debris.

   the passage

   Inspect the IP to body harness connector terminals for corrosion and debris.

Repair

1. If a water leak is observed, repair it as necessary and verify that the repair is effective.

   the passage

   If a water leak is observed, repair as necessary. Verify the effectiveness of the repair.

2. If any corrosion and/or debris is observed, repair as necessary.

   the passage

   If any corrosion and/or debris is observed, repair as necessary.