Throttle/Pedal Position Sensor/Switch "F" Circuit Low
The engine computer detected an unusually low voltage signal from the throttle position sensor (TPS) circuit, indicating either a wiring problem or sensor failure. This prevents the engine from accurately reading throttle position, affecting fuel delivery and idle control.
What You Might Notice
- Rough or unstable idle
- Engine stalling at stops
- Engine surging or hesitation
- Reduced or no acceleration response
- Check engine light illumination
Most Common Causes
- 1
Faulty Throttle Position Sensor
The TPS has failed internally or developed a short circuit, causing it to send an abnormally low voltage signal to the PCM.
- 2
Wiring Short to Ground
The TPS circuit wiring is shorted to ground or another wire, creating a low-voltage condition that the computer interprets as a sensor fault.
- 3
Loose or Damaged TPS Connector
Poor electrical connection at the TPS connector or corroded terminals can cause intermittent or continuous low-voltage signals.
- 4
PCM or Wiring Harness Damage
Damaged engine control module circuitry or corroded wiring harness connectors can prevent proper voltage signals from reaching the computer.
How to Diagnose It
- 1
Check Faulty Throttle Position Sensor — The TPS has failed internally or developed a short circuit, causing it to send an abnormally low voltage signal to the PCM.
- 2
Check Wiring Short to Ground — The TPS circuit wiring is shorted to ground or another wire, creating a low-voltage condition that the computer interprets as a sensor fault.
- 3
Check Loose or Damaged TPS Connector — Poor electrical connection at the TPS connector or corroded terminals can cause intermittent or continuous low-voltage signals.
- 4
Check PCM or Wiring Harness Damage — Damaged engine control module circuitry or corroded wiring harness connectors can prevent proper voltage signals from reaching the computer.
How to Fix It
- 1
Inspect and Secure TPS Connector
Check the throttle position sensor connector for corrosion, loose pins, or damage. Clean with electrical contact cleaner and reseat firmly. Verify all connector contacts are properly crimped.
- 2
Test and Replace TPS if Faulty
Use a multimeter to measure TPS voltage output at idle and full throttle. If voltage does not increase smoothly from approximately 0.5V to 4.5V, replace the throttle position sensor.
- 3
Inspect TPS Wiring for Shorts
Visually inspect the TPS wiring harness from the sensor to the PCM for cuts, abrasions, or pinched areas. Use a multimeter in ohms mode to check for continuity faults or shorts to ground. Repair or replace damaged wiring.
- 4
Scan for Additional Codes and Verify PCM
Clear the code and perform a full system scan to check for related DTCs that might indicate PCM failure. If code returns and wiring/sensor are confirmed good, have the PCM tested or replaced by a specialist.
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