Throttle/Pedal Position Sensor/Switch C Circuit Low Input
The engine control module detected that Throttle Position Sensor C circuit voltage is abnormally low, indicating a short to ground or sensor failure. This prevents the PCM from accurately measuring throttle position, affecting fuel delivery and engine timing.
What You Might Notice
- Rough or unstable idle
- Engine stalling at stops
- Surging or hesitation during acceleration
- Reduced or no acceleration response
- Check Engine Light illuminated
Most Common Causes
- 1
Faulty Throttle Position Sensor
The TPS potentiometer internally fails or develops a short to ground, causing the circuit voltage to drop below the normal operating range.
- 2
TPS circuit short to ground or crossed wire
A wiring harness defect, pinched wire, or loose connector causes the TPS signal line to short to ground or another vehicle circuit, pulling voltage below acceptable levels.
- 3
TPS not mounted securely
Loose mounting of the throttle position sensor allows intermittent connection or changes the sensor's internal resistance, creating low voltage signals.
- 4
Damaged PCM or defective wiring connections
Corroded battery terminals, loose grounds, or internal PCM damage can cause improper voltage regulation to the TPS circuit.
How to Diagnose It
- 1
Check Faulty Throttle Position Sensor — The TPS potentiometer internally fails or develops a short to ground, causing the circuit voltage to drop below the normal operating range.
- 2
Check TPS circuit short to ground or crossed wire — A wiring harness defect, pinched wire, or loose connector causes the TPS signal line to short to ground or another vehicle circuit, pulling voltage below acceptable levels.
- 3
Check TPS not mounted securely — Loose mounting of the throttle position sensor allows intermittent connection or changes the sensor's internal resistance, creating low voltage signals.
- 4
Check Damaged PCM or defective wiring connections — Corroded battery terminals, loose grounds, or internal PCM damage can cause improper voltage regulation to the TPS circuit.
How to Fix It
- 1
Inspect and test Throttle Position Sensor
Use a multimeter to measure TPS voltage at idle and full throttle. If voltage stays below 0.5V or fails to sweep smoothly, replace the sensor.
- 2
Check TPS wiring harness and connectors
Visually inspect the TPS circuit wiring for pinches, cuts, or corrosion. Disconnect and reconnect the TPS connector firmly. Check for moisture or corrosion at the connector terminals and clean if necessary.
- 3
Verify TPS mounting and alignment
Remove the TPS and inspect mounting holes for damage. Reinstall securely with correct alignment to the throttle shaft. Ensure all fasteners are tight and the sensor rotates smoothly without binding.
- 4
Test PCM power and grounds
Check battery voltage and main ground connections. Measure voltage supply to TPS circuit at the PCM connector. If voltage is low, repair battery terminals and grounds; if still faulty, PCM replacement may be necessary.
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