P2122Powertrain
Powertrain · SAE
Accelerator Pedal Position Sensor D — Low Signal
Meaning
The signal voltage of the accelerator pedal position (APP) sensor track D is below the minimum acceptable threshold (typically < 0.2 V). A low signal indicates a short to ground, an open circuit, or an internally failed sensor on track D of the pedal sensor.
Common causes
- Short to ground on the APP track D signal wire
- Open circuit in the track D wiring
- Internal short to ground in the APP sensor on track D
- Corroded or loose pedal sensor connector
- Failed 5 V reference supply for the D circuit
Symptoms
- Check-engine light (MIL) on
- Limp-home mode with throttle limitation
- Absent or severely reduced pedal response
- Often associated code P2138 (D/E correlation fault)
- Engine speed locked at idle in some cases
Severity
High: loss of APP D signal activates limp-home mode; the vehicle is barely drivable.
What to do
- Measure APP D signal voltage at the connector (0.5–4.5 V with pedal released/fully depressed)
- Disconnect the sensor and measure voltage on signal wire D: if still low, short to ground in the wiring
- Check the 5 V reference supply at the sensor
- Inspect the pedal sensor connector for corrosion and intermittent contacts
- Replace the APP sensor if the short is internal