Throttle/Pedal Position Sensor/Switch B Circuit Low Input
The engine computer detected that Throttle Position Sensor B is sending a voltage signal that is lower than the expected minimum threshold. This sensor monitors throttle blade position to tell the engine how much fuel and air to inject, so a faulty signal disrupts engine control and drivability.
What You Might Notice
- Rough or unstable idle
- Engine stalling at stops
- Surging or hesitation during acceleration
- Little to no acceleration response
- Check Engine Light illuminated
Most Common Causes
- 1
Faulty Throttle Position Sensor B
The TPS B sensor itself has failed or is outputting an incorrect low voltage signal. This is the most common cause and requires sensor replacement.
- 2
TPS Circuit Short to Ground
A wiring harness connected to the TPS has a short circuit, pulling the voltage signal down to ground level. This creates an artificially low reading at the PCM.
- 3
Loose or Improperly Mounted TPS
The throttle position sensor is not securely fastened to the throttle body, causing poor electrical contact or intermittent signal loss.
- 4
Engine Control Module (PCM) Failure
Rarely, the PCM itself may have a fault in the circuit that reads the TPS signal, though this is uncommon compared to sensor and wiring issues.
How to Diagnose It
- 1
Check Faulty Throttle Position Sensor B — The TPS B sensor itself has failed or is outputting an incorrect low voltage signal. This is the most common cause and requires sensor replacement.
- 2
Check TPS Circuit Short to Ground — A wiring harness connected to the TPS has a short circuit, pulling the voltage signal down to ground level. This creates an artificially low reading at the PCM.
- 3
Check Loose or Improperly Mounted TPS — The throttle position sensor is not securely fastened to the throttle body, causing poor electrical contact or intermittent signal loss.
- 4
Check Engine Control Module (PCM) Failure — Rarely, the PCM itself may have a fault in the circuit that reads the TPS signal, though this is uncommon compared to sensor and wiring issues.
How to Fix It
- 1
Replace Throttle Position Sensor B
Remove the old TPS from the throttle body and install a new sensor, ensuring proper seating and secure fastening. Reconnect the electrical connector and clear the code to verify the repair.
- 2
Inspect and Repair TPS Wiring Harness
Check the TPS electrical connector and wiring for damage, corrosion, or shorts to ground. Repair or replace damaged wiring segments and ensure all connections are clean and tight.
- 3
Secure or Reseat the TPS
Remove the sensor, inspect the mounting surface for debris or damage, then reinstall the TPS with proper fastener torque. Verify the connector is fully seated before testing.
- 4
Test and Replace Engine Control Module
If all other repairs fail, have the PCM tested by a professional diagnostician. If faulty, reprogram or replace the module and recalibrate throttle settings.
Need a deeper diagnosis?
Search for related repair guides or browse by system.