NOx Sensor Heater Sense Circuit Bank 2
The P2221 code indicates a malfunction in the heater sense circuit of the NOx sensor on Bank 2. The NOx sensor measures nitrogen oxide levels in the exhaust and requires a heater to reach operating temperature quickly. The heater sense circuit monitors the heater's current draw; if it's out of range, the PCM sets this code. This can lead to inaccurate NOx readings, affecting emissions and potentially triggering the check engine light.
01. Most Common Causes
- Faulty NOx sensor heater element
- Open or short in heater circuit wiring
- Blown fuse or relay for NOx sensor heater
- Corroded or damaged connector at sensor
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Possible reduced fuel economy
- Possible rough idle or hesitation
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect NOx sensor connector and wiring for damage or corrosion.
Step 3: Using a multimeter, check heater circuit resistance at sensor connector (typically 2-10 ohms).
Step 4: Check for battery voltage and ground at the heater circuit with key on.
Step 5: If voltage and ground are present but resistance is out of spec, replace the NOx sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but the vehicle may fail emissions and fuel economy could suffer. It's best to repair promptly.
How much does it cost to fix?▼
Typically $200-$600 including parts and labor, depending on sensor cost and accessibility.