Throttle/Pedal Position Sensor/Switch E Circuit High
What does P2128 mean?
The P2128 code means the vehicle's onboard diagnostic system has detected: Throttle/Pedal Position Sensor/Switch E Circuit High. This is a critical severity code.
Common Symptoms
- Reduced power mode
- Engine may idle high
- Potential unintended acceleration concern
- Throttle/pedal warning light on
- Check engine light on
Probable Causes (Ranked by Likelihood)
- APP sensor E signal wire open or shorted to reference voltage Very High
- Disconnected APP sensor connector High
- Faulty APP sensor E track (stuck high) Moderate
- Wiring damage causing signal-to-reference short Moderate
- PCM input circuit issue Low
Step-by-Step Diagnostic Procedure
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Verify APP sensor connector is fully plugged in
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Check APP sensor E voltage at rest -- should be within spec, not at or near 5V
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Disconnect sensor and verify voltage on E signal wire drops -- if still at 5V, check for wire-to-wire shorts
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Inspect wiring harness where signal and reference wires run parallel for chafing damage
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Replace APP sensor assembly if sensor is confirmed faulty with good wiring
Frequently Asked Questions
Can I drive with code P2128?
No. A high signal on the E circuit could indicate the PCM is reading full throttle when the pedal is not pressed. The PCM enters reduced power mode as a safety measure. Have the vehicle towed for diagnosis.
Is this code related to unintended acceleration recalls?
This type of code was involved in some manufacturer investigations of unintended acceleration. However, modern PCMs have multiple safety checks to prevent unintended acceleration even when one sensor fails. The reduced power mode is one of these safeguards.
Why does a disconnected connector cause a high reading?
The PCM supplies a 5V reference to the APP sensor. When the sensor is disconnected, the signal wire floats to the reference voltage because there is no sensor to pull it to the correct level. The PCM reads this 5V as a high circuit condition.