Throttle Position Sensor Circuit Low Input
The P0122 code indicates that the Engine Control Module (ECM) has detected a low voltage signal from the throttle position sensor (TPS) circuit A. The TPS is a potentiometer that tells the ECM how far the throttle plate is open. A low input means the voltage is below the expected range (typically below 0.2-0.5 volts at idle). This can cause incorrect air-fuel mixture, poor acceleration, and limp mode.
1. Most Common Causes
- Faulty throttle position sensor
- Open or shorted wiring in TPS circuit
- Poor electrical connection at TPS connector
- Failed ECM (rare)
2. Symptoms You Will Notice
- Check Engine Light on
- Poor acceleration or hesitation
- Engine stalling or rough idle
- Reduced power or limp mode
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify P0122 and check live TPS voltage at idle (should be ~0.5V).
Step 2: Inspect TPS connector for corrosion, bent pins, or loose wires.
Step 3: Test TPS signal voltage while manually opening throttle (should rise smoothly to ~4.5V).
Step 4: Check for open/short in wiring between TPS and ECM using a multimeter.
Step 5: If all checks pass, replace TPS and clear code.
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, depending on vehicle and shop rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.