Reductant Quality Sensor Circuit High
The P206D code indicates that the reductant quality sensor circuit in the selective catalytic reduction (SCR) system has detected a voltage higher than the expected range. This sensor monitors the quality of diesel exhaust fluid (DEF) to ensure proper NOx reduction. A high circuit signal can be caused by a faulty sensor, wiring issues, or contamination in the DEF system.
1. Most Common Causes
- Faulty DEF quality sensor (internal failure)
- Signal wire shorted to battery voltage or reference voltage
- Open circuit in sensor ground or 5V reference wire
- Corroded, loose, or damaged pins/connectors in SCR sensor harness
- Internal failure of SCR control module or ECM
- Severe DEF fluid contamination causing incorrect sensor readings
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power
- Increased emissions
- Possible limp mode activation
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all codes and freeze frame data.
Step 2: Inspect the reductant quality sensor connector and wiring for damage, corrosion, or shorts.
Step 3: Test the sensor's voltage and resistance per manufacturer specifications.
Step 4: Check DEF fluid quality and level; replace if contaminated.
Step 5: If sensor and wiring are okay, replace the reductant quality sensor.
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 engine performance and increased emissions. The vehicle may enter limp mode to protect the SCR system.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the sensor price and shop rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.