P2205

What the Code Means

P2205 — NOx sensor heater circuit malfunction, bank 1 sensor 1. The code means the engine control unit (DME) has detected a deviation in the sensor heater: circuit resistance or current draw is outside the allowed range, or the heater doesn't reach the required temperature within the allotted time.

The NOx sensor sits in the exhaust system and monitors nitrogen oxide concentration upstream and downstream of the SCR catalyst. To reach operating temperature quickly after a cold start, the sensor has a built-in heater. The DME controls the heater via pulse-width modulation and monitors the circuit by current and voltage. When it detects a mismatch, it sets P2205.

Possible causes:

• faulty NOx sensor heater element;
• wiring problems (open circuit, short circuit, corroded contacts);
• faulty control unit (DME).

Symptoms

• Increased fuel consumption.
• Problems with the SCR (selective catalytic reduction) system.
• Check Engine light comes on.

Diagnosis and Repair

1. Read the fault codes with diagnostic equipment (ISTA, INPA) and check for related errors in the SCR system and NOx sensor.
2. Check the heater circuit: measure the NOx sensor heater element resistance and compare it to spec; check the wiring for open circuit, short circuit, and secure connector contacts.
3. Replace the NOx sensor if needed (bank 1, sensor 1).
4. Check the control unit (DME) if there are no faults in the circuit or sensor.