Reductant Quality Sensor Circuit High
The P206D code indicates that the reductant quality sensor, which monitors the quality of diesel exhaust fluid (DEF) in the selective catalytic reduction (SCR) system, is reporting a voltage signal that is higher than the expected range. This sensor is typically a two-wire or three-wire sensor that measures the concentration of urea in the DEF. A high circuit voltage can be caused by a faulty sensor, wiring issues, or a problem with the DEF itself. The SCR system relies on proper DEF quality to reduce NOx emissions, so this code can lead to reduced engine performance and increased emissions.
01. Most Common Causes
- Faulty reductant quality sensor
- Short to voltage in the sensor circuit
- Open or high resistance in the sensor ground circuit
- Corroded or damaged wiring/connectors
- Contaminated or incorrect DEF fluid
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Increased diesel exhaust fluid consumption
- Poor fuel economy
- Failed emissions test
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the reductant quality sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage reference and ground circuits using a multimeter; compare to manufacturer specifications.
Step 4: If circuits are okay, test the sensor's output voltage while varying DEF quality (if possible) or replace the sensor.
Step 5: Clear the code and test drive to see if it returns.
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 reduced engine performance and potential damage to the SCR system. The vehicle may enter limp mode to protect the emissions system.
How much does it cost to fix?▼
The cost to fix P206D typically ranges from $50 to $150 for diagnosis and sensor replacement, but can be higher if wiring repairs are needed or if the DEF fluid needs to be replaced.