Throttle/Pedal Position Sensor Circuit Malfunction
Code P2120 indicates a problem in the throttle/pedal position sensor/switch circuit, specifically the 'D' circuit. This sensor is critical for determining driver demand and throttle position. When the PCM detects a voltage or signal outside the expected range, it sets this code. Common causes include a faulty sensor, wiring issues, or a defective accelerator pedal assembly.
1. Most Common Causes
- Faulty accelerator pedal position (APP) sensor
- Faulty throttle position sensor (TPS)
- Short to ground or voltage in circuit D wiring
- Open circuit or high resistance in sensor wiring or connectors
- Loose connection, corroded terminals, or bent pins in the harness
- Internal engine control module (ECM/PCM) failure
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Poor acceleration or hesitation
- Erratic throttle response or surging
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm code P2120 and check for additional codes.
Step 2: Visually inspect the wiring and connectors for damage, corrosion, or loose connections.
Step 3: Test the sensor voltage and resistance with a multimeter per manufacturer specifications.
Step 4: If sensor tests faulty, replace the throttle position sensor or accelerator pedal assembly as needed.
Step 5: Clear codes and test drive to verify repair.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The vehicle may enter limp mode, limiting speed and acceleration, which can be dangerous in traffic.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, but costs can vary depending on the vehicle and whether the sensor or pedal assembly needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.