P2209Powertrain
Powertrain · SAE
NOx Reductant Temperature Sensor — Circuit
Meaning
The reductant (AdBlue/DEF) temperature sensor in the SCR system has a circuit fault. The sensor monitors the temperature of the AdBlue fluid in the tank or dosing line to manage heating and prevent freezing or overheating of the reductant.
Common causes
- Damaged or oxidised connector or wiring on the AdBlue temperature sensor
- Internally failed reductant temperature sensor
- Short circuit or open circuit in the signal line
- Missing supply voltage or ground at the sensor
- Sensor contaminated by AdBlue crystals blocking electrical contact
Symptoms
- Check engine or AdBlue warning light on
- AdBlue temperature data absent or fixed on scan tool
- AdBlue heating system not correctly managed (risk of freezing)
- Possible damage to AdBlue tank or pump from uncontrolled temperature
- Related SCR codes possible
Severity
Moderate: a non-functioning temperature sensor compromises AdBlue system management, especially in cold climates where the fluid can freeze (AdBlue freezing point: -11 °C).
What to do
- Inspect the sensor connector and wiring for oxidation or damage
- Check supply voltage and ground at the sensor
- Measure NTC sensor resistance as a function of temperature and compare with manufacturer table
- Clean any AdBlue crystal deposits around the sensor
- Replace the sensor if defective, after ruling out the wiring as the cause