Throttle/Pedal Pos Sensor/Switch D / E Voltage Correlation
P2138 indicates a voltage correlation mismatch between two throttle or pedal position sensors (typically sensors D and E). The engine control module detects that these redundant sensors are not reading consistently, which compromises the vehicle's ability to accurately determine driver intent and throttle position.
What You Might Notice
- Check engine light illuminated
- Stalling at stops or idle
- Loss of power or no acceleration response
- Sudden power loss during cruise
- Stuck throttle at fixed RPM
Most Common Causes
- 1
Throttle position sensor failure
One or both throttle position sensors (TPS) have failed, drifted out of calibration, or are producing inconsistent voltage signals. This is the most common cause of P2138.
- 2
Accelerator pedal position sensor malfunction
The electronic accelerator pedal contains dual sensors that may be failing, corroded, or losing calibration, causing voltage mismatch between sensor D and E.
- 3
Wiring or connector issues
Corroded, damaged, or loose connectors and wiring harnesses between the sensors and ECM can cause signal degradation or intermittent voltage correlation problems.
- 4
Engine control module (ECM) fault
Rarely, a faulty ECM or PCM may incorrectly interpret valid sensor signals or have internal processing errors, though sensor failure is far more common.
How to Diagnose It
- 1
Check Throttle position sensor failure — One or both throttle position sensors (TPS) have failed, drifted out of calibration, or are producing inconsistent voltage signals. This is the most common cause of P2138.
- 2
Check Accelerator pedal position sensor malfunction — The electronic accelerator pedal contains dual sensors that may be failing, corroded, or losing calibration, causing voltage mismatch between sensor D and E.
- 3
Check Wiring or connector issues — Corroded, damaged, or loose connectors and wiring harnesses between the sensors and ECM can cause signal degradation or intermittent voltage correlation problems.
- 4
Check Engine control module (ECM) fault — Rarely, a faulty ECM or PCM may incorrectly interpret valid sensor signals or have internal processing errors, though sensor failure is far more common.
How to Fix It
- 1
Inspect and test throttle/pedal position sensors
Use a multimeter to measure voltage output from both sensor D and E across their full operating range. Compare readings to manufacturer specifications. Replace any sensor that reads outside acceptable range or does not respond smoothly to pedal movement.
- 2
Check sensor connectors and wiring
Visually inspect all connectors between sensors and ECM for corrosion, loose pins, or damaged terminals. Clean connectors with electrical contact cleaner and ensure snug connections. Replace any damaged wiring harness sections.
- 3
Perform throttle relearn procedure
After sensor replacement or repair, many vehicles require a throttle relearn or calibration procedure where the ECM resets sensor baseline values. Consult your vehicle's service manual for the specific procedure, which may involve key cycling, idle adjustments, or scan tool commands.
- 4
Replace engine control module if sensors are good
If both sensors test within specifications and wiring is intact but the code persists, the ECM may be faulty. This is uncommon but can occur. Replacement ECM may require reprogramming.
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