P229F62

What the Code Means

P229F62 flags a fault in the nitrogen oxide (NOx) sensor on bank 2 of the SCR AdBlue exhaust aftertreatment system. The sensor measures NOx content in the exhaust, and the control unit uses its readings to meter AdBlue injection.

The cause can be an open circuit or short in the sensor circuit, soot contamination of the sensing element, or failure of the sensor itself. When the signal is lost, the DME can no longer manage AdBlue dosing correctly, which shows up as a Check Engine light and possible power limitation.

Symptoms

• Check Engine light on the instrument cluster;
• “check AdBlue” message;
• possible engine power limitation;
• black smoke from the exhaust;
• increased fuel consumption.

Diagnosis and Repair

Step 1. Read the Codes

Read fault codes with the ISTA diagnostic tool and note any related faults in the NOx sensor circuit.

Step 2. Check the Wiring

Check the bank 2 NOx sensor wiring for open circuit and short. If the problem is in the circuit, repair the damage — the sensor does not need replacement when the wiring is good.

Step 3. Clean the Sensor

If the sensing element is contaminated with soot, the sensor can be cleaned. If cleaning does not restore operation, replace the NOx sensor (the OEM part number depends on the specific model — look it up in ETK).

Step 4. Reset Adaptations

After the fault is fixed, reset the DME adaptations so the control unit recalibrates the system to the new sensor’s readings.

Secondary Problems

• soot buildup in the DPF and catalytic converter;
• reduced SCR aftertreatment efficiency;
• catalytic converter damage that requires replacement — an expensive repair, so don’t put off fixing the fault.