Reductant Metering Unit Temperature Sensor Circuit Range/Performance
The P20AD code indicates that the reductant metering unit temperature sensor circuit is out of expected range or has a performance issue. This sensor monitors the temperature of the diesel exhaust fluid (DEF) in the metering unit, which is critical for proper injection into the exhaust stream. A faulty sensor or circuit can lead to incorrect DEF dosing, potentially causing increased emissions and triggering the check engine light.
1. 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
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Connect a scan tool and verify the P20AD code. Check for additional related codes.
Step 2: Visually inspect the reductant metering unit temperature sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Use a multimeter to test the sensor's resistance and compare to manufacturer specifications. Also check for continuity and shorts in the wiring.
Step 4: If the sensor and wiring are okay, test the ECM output signals to the sensor circuit. Replace the sensor if it fails the resistance test.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally 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. Limp mode may also be activated, reducing vehicle performance.
How much does it cost to fix?▼
The cost to fix P20AD typically ranges from $50 to $150, including parts and labor. The sensor itself is relatively inexpensive, but diagnostic time and labor can add to the cost.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.