NOx Sensor Heater Control Circuit/Open Bank 2
The P2218 code indicates a problem with the heater circuit of the NOx sensor on Bank 2 (the side of the engine opposite cylinder #1). The NOx sensor measures nitrogen oxide levels in the exhaust to help the diesel or lean-burn gasoline engine control system reduce emissions. The heater element is essential for the sensor to reach operating temperature quickly, especially during cold starts. An open circuit means there is a break in the electrical path, preventing the heater from functioning. This can be caused by a faulty sensor, damaged wiring, or a blown fuse.
1. Most Common Causes
- Faulty NOx sensor with internal heater element failure
- Open or short circuit in the NOx sensor heater wiring
- Damaged or corroded NOx sensor connector
- Blown NOx sensor heater fuse
- Failed PCM or emissions control module (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Possible reduced fuel economy
- Possible engine performance issues (hesitation, rough idle)
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes (e.g., P2201, P2217).
Step 2: Visually inspect the NOx sensor connector and wiring for damage, corrosion, or loose connections.
Step 3: Test the heater circuit resistance at the sensor connector using a multimeter (typically 2-10 ohms). If open, replace the sensor.
Step 4: Check the fuse and relay for the NOx sensor heater circuit; replace if blown.
Step 5: If wiring and fuses are good, replace the NOx sensor on Bank 2.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances, but the vehicle may fail emissions and could experience reduced fuel economy or performance. It's best to repair promptly to avoid further issues.
How much does it cost to fix?▼
Replacing a NOx sensor typically costs $150-$400 including parts and labor. DIY replacement can be cheaper if you buy the sensor ($100-$250) and do the work yourself.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.