Reductant Metering Unit Temperature Sensor Circuit Low
The P20AE code indicates that the reductant metering unit temperature sensor circuit is reporting a voltage lower than the expected range. 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 low circuit signal can be caused by a faulty sensor, wiring issues, or a problem with the DEF heater. This 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
- Short to ground in the sensor circuit wiring
- Corroded or damaged connector at the sensor
- Failed DEF heater causing sensor misreading
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Possible failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes (e.g., P20AF).
Step 2: Visually inspect the sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor resistance with a multimeter; compare to manufacturer specifications.
Step 4: Check for shorts to ground in the circuit by disconnecting the sensor and measuring continuity.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can lead to reduced performance, increased emissions, and potential damage to the DEF system. Limp mode may activate.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the sensor or wiring needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.