P0120Powertrain
Powertrain · SAE
TPS/Accelerator Pedal Sensor A — Circuit Fault
Meaning
The ECU has detected a general fault in the throttle position or accelerator pedal position sensor circuit, track A: the signal voltage is out of range, absent, or implausible relative to operating conditions.
Common causes
- Faulty TPS/APP sensor (internal track A failure)
- Damaged wiring: short circuit or open circuit on signal A
- Corroded, loose, or deformed connector
- Degraded or lost 5 V reference supply from the ECU
- Sensor ground fault
Symptoms
- Check-engine light (MIL) on
- Fail-safe mode with throttle limitation
- Abnormal or absent accelerator response
- Unable to exceed a certain engine speed
- Possible stall on deceleration
Severity
High: an invalid TPS signal activates limp-home mode; drivability is severely compromised.
What to do
- Measure TPS track A signal voltage at the ECU connector (0.5–4.5 V with pedal released/fully depressed)
- Verify the 5 V reference supply at the sensor
- Check wiring and connectors for shorts, open circuits, and corrosion
- Test the TPS/APP sensor with a multimeter and compare with specifications
- Replace the sensor if out of specification