Reductant Metering Unit Temperature Sensor Circuit Malfunction
The P20AC code indicates a problem in the reductant metering unit temperature sensor circuit, which is part of the Selective Catalytic Reduction (SCR) system. This sensor monitors the temperature of the diesel exhaust fluid (DEF) or reductant to ensure proper injection into the exhaust stream. A fault in this circuit can lead to incorrect DEF dosing, potentially causing increased emissions, reduced fuel economy, and possible damage to the SCR system.
01. Most Common Causes
- Faulty reductant metering unit temperature sensor
- Open or shorted wiring in the sensor circuit
- Poor electrical connection at the sensor or ECM
- Corroded or damaged connector pins
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power
- Increased exhaust emissions
- Possible DEF system warnings or messages
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the P20AC code and check for any related codes.
Step 2: Visually inspect the reductant metering unit temperature sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's resistance and compare with manufacturer specifications; replace if out of range.
Step 4: Check the circuit for continuity and shorts using a multimeter; repair any wiring issues found.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can lead to improper DEF dosing, increased emissions, and potential damage to the SCR system. You may experience reduced performance and fuel economy.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the sensor needs replacement or just a wiring repair.