Accelerator pedal position sensor codes

How its codes differ

• P2122 is a circuit-low code on one pedal signal: the voltage is lower than the sensor should ever produce, which points to a wire shorted to ground, a poor connection or the sensor itself.
• P2138 means two pedal signals no longer agree with each other. A worn sensor track or a poor connection anywhere between the pedal and the computer can cause it.
• Throttle body codes (P2111, P2112, P2119, P2135) also cause reduced power, but the fault is at the throttle, not the pedal. P2135 can involve either sensor set, so check which signals the code names for your vehicle.
• On some FCA vehicles, P2122 can be set just by unplugging the pedal during an earlier diagnosis, so confirm the code comes back before replacing anything.

Codes

• P2122

  The signal from accelerator pedal position sensor D (usually the first pedal sensor) is lower than its normal range

  Severity: Inspect soon

• P2138

  Two accelerator pedal position sensor signals (D and E) that should agree with each other don't

  Severity: Inspect soon

Signs it's failing

• Check engine light with a reduced-power message
• Limp mode with poor or no response to the pedal
• Engine idling higher than normal
• Hesitation or surging that comes and goes

How to test it

1. Read all stored codes with a scan tool, clear them once, and see whether the pedal code returns. A code that does not come back may be left over from earlier work. (Low risk)

2. With the ignition off, look at the pedal connector and the harness you can see under the dash for a loose plug, stretched terminals or damaged wires. (Low risk)

3. Measuring the pedal signals and testing the wiring back to the engine computer are jobs for a shop with a scan tool and meter or scope. (Best left to a shop)

   Warning: Back-probing connectors with the wrong tools can damage terminals and create a new fault. Never test the pedal by pressing it with the engine running and the car in gear.

After the repair

• Check whether your vehicle has a special coverage or bulletin for the pedal or its connection before paying for a pedal assembly.
• Clear codes only after the repair, then test drive and confirm the reduced-power warning does not return.