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 measures the angle of the throttle plate and sends a voltage signal to the ECM to determine driver demand. A high input can be caused by a faulty sensor, wiring issues, or a problem with the ECM itself. This code often triggers the check engine light and may affect vehicle performance.
1. Most Common Causes
- Faulty throttle position sensor
- Short to voltage in TPS signal circuit
- Open or shorted TPS ground circuit
- Corroded or damaged TPS connector
- Failed ECM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor acceleration or hesitation
- Engine stalling or rough idle
- Reduced fuel economy
- Vehicle may enter limp mode
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for additional codes.
Step 2: Visually inspect the TPS connector and wiring for damage, corrosion, or loose connections.
Step 3: With key on engine off, measure TPS signal voltage at the sensor connector; should be 0.5-1.0V at closed throttle and 4.5-5.0V at wide open throttle.
Step 4: Check for a short to voltage by disconnecting the sensor and checking if signal wire voltage drops to 0V.
Step 5: If voltage is normal, replace the TPS sensor; if not, repair wiring or replace ECM.
4. 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 limp mode, which may lead to unsafe driving conditions.
How much does it cost to fix?▼
The cost to fix P0123 typically ranges from $50 to $150 for a new TPS sensor plus labor, but could be higher if wiring repairs or ECM replacement is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.