Parts
$20–90
P0122 — Throttle Position Sensor Circuit Low Voltage
CAUTIONIs it safe to drive? Driveable at low speeds but the ECU cannot read throttle input accurately — avoid highway driving until repaired.
What P0122 means
The TPS signal wire reads below 0.2–0.3V, which falls outside the valid range. At idle the TPS should read roughly 0.5V and should never drop below that threshold in normal operation.
Most likely causes (in order)
- Shorted signal wire — most common wiring fault
- Failed TPS sensor (internal short, $20–90)
- Poor ground connection at the TPS
- Damaged wiring harness near the throttle body (heat/abrasion zone)
Symptoms you might notice
- Rough or unstable idle
- Hesitation from a stop
- Engine may stall when throttle is applied
- Poor acceleration
- Transmission may default to limp mode on automatics
What to check first
Backprobe the TPS signal wire at the connector with the key on — you should read ~0.5V at closed throttle. If it reads 0V, disconnect the sensor; if voltage rises to ~5V with the sensor unplugged, the sensor itself is shorted internally. If it stays at 0V, the signal wire is shorted to ground.
Repair cost & difficulty
Labor
0.3–0.7 hr
Difficulty
DIY-friendly