Throttle Position Sensor Circuit High Input
The P0123 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the throttle position sensor (TPS) that is higher than the expected range (typically above 4.5 volts). This sensor monitors the throttle plate angle and sends a voltage signal to the ECM to adjust fuel injection and ignition timing. A high input can be caused by a faulty sensor, wiring issues, or a short to voltage. This condition can lead to poor engine performance, reduced fuel economy, and potential safety concerns if the throttle response is erratic.
01. Most Common Causes
- Faulty throttle position sensor
- Short to voltage in the TPS signal circuit
- Damaged wiring or connector at TPS
- Corroded or loose electrical connections
- ECM failure (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor acceleration or hesitation
- Engine stalling or rough idle
- Reduced fuel economy
- Throttle response erratic or unresponsive
03. Step-by-Step Diagnosis
Step 1: Connect an OBD2 scanner and verify the code P0123. Check for additional codes.
Step 2: Visually inspect the TPS wiring and connector for damage, corrosion, or loose pins.
Step 3: Using a multimeter, check the TPS signal voltage at the sensor connector (should be 0.5-4.5V depending on throttle position).
Step 4: If voltage is high (e.g., 5V constant), disconnect the TPS and check if voltage drops; if not, there is a short to voltage in the wiring.
Step 5: Test the TPS resistance across its terminals; replace if out of spec.
Step 6: Clear the code and test drive to see if it returns. If it does, replace the TPS.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with P0123 as it can cause unpredictable throttle response, stalling, or loss of power, which may lead to accidents. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor. A new throttle position sensor costs around $20-$60, and labor is about $30-$90 depending on the vehicle.