Throttle Position Sensor Circuit Malfunction
The P0120 code indicates a malfunction in the throttle position sensor (TPS) circuit A. The TPS is a potentiometer that sends the throttle plate position to the engine control module (ECM). When the ECM detects an abnormal voltage signal from the TPS, it sets this code. This can cause poor engine performance, stalling, and reduced fuel economy.
01. Most Common Causes
- Faulty throttle position sensor
- Wiring or connector issues in the TPS circuit
- Carbon buildup on throttle body affecting sensor operation
- ECM failure (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor acceleration or hesitation
- Engine stalling or rough idle
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect TPS wiring and connector for damage or corrosion.
Step 3: Test TPS voltage signal with a multimeter; should vary smoothly from ~0.5V at closed throttle to ~4.5V at wide open throttle.
Step 4: Check throttle body for carbon buildup and clean if necessary.
Step 5: If sensor fails voltage test, replace TPS and clear codes.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the vehicle may stall or have reduced power, posing a safety risk.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the vehicle and shop rates.