Throttle/Pedal Position Sensor Circuit High Input
The P2123 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the throttle position sensor (TPS) or accelerator pedal position sensor (APP) that is higher than the expected range. This typically means the signal voltage is above the normal operating range (e.g., >4.5V). The sensor is a potentiometer that provides a variable voltage based on pedal or throttle position. A high input can be caused by a short to voltage in the wiring, a faulty sensor, or an ECM issue. This code often triggers the check engine light and may cause reduced engine power or limp mode.
1. Most Common Causes
- Faulty throttle position sensor (TPS) or accelerator pedal position sensor (APP)
- Short to voltage in the sensor signal circuit
- Corroded or damaged wiring/connectors
- Failed ECM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Poor acceleration or hesitation
- Erratic idle or stalling
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the TPS/APP sensor wiring and connectors for damage, corrosion, or loose connections.
Step 3: With the key on, engine off, measure the signal voltage at the sensor connector. Compare to manufacturer specs (typically 0.5-4.5V).
Step 4: If voltage is high (>4.5V), check for a short to 5V reference or battery voltage in the signal wire.
Step 5: If wiring is okay, replace the sensor and clear the code. Re-test to see if code returns.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with P2123 as it can cause sudden loss of throttle response or unintended acceleration. The vehicle may enter limp mode, limiting speed. Have it diagnosed promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a DIY sensor replacement. At a shop, expect $100-$250 including labor and parts.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.