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. This typically means the sensor output is below the expected range (usually below 0.2-0.5 volts at idle). The TPS is a potentiometer that tells the ECM the position of the throttle plate. A low input can be caused by a faulty sensor, wiring issues (short to ground, open circuit), poor connections, or a problem with the ECM itself. This code often leads to poor engine performance, reduced power, and may trigger limp mode.
01. Most Common Causes
- Faulty throttle position sensor
- Open or shorted wiring in the TPS circuit
- Poor electrical connection at the TPS connector
- Corroded or damaged terminals
- Failed ECM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor acceleration or hesitation
- Engine stalling or rough idle
- Reduced power or limp mode
- Increased fuel consumption
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect TPS connector and wiring for damage, corrosion, or loose connections.
Step 3: Using a multimeter, check TPS reference voltage (typically 5V) and ground at the connector.
Step 4: With the connector attached, backprobe the signal wire and measure voltage at idle (should be ~0.5-1.0V) and at wide open throttle (should be ~4.5V).
Step 5: If voltage is low, disconnect the TPS and check resistance across the sensor terminals; replace if out of spec.
Step 6: If sensor is good, check for shorts to ground or opens in the wiring between TPS and ECM.
04. Commonly Affected Makes
05. 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. Additionally, poor engine performance could lead to stalling.
How much does it cost to fix?▼
Typically between $50 and $150 for parts and labor. A new TPS sensor costs around $20-$60, and labor is about $30-$90 depending on the vehicle.