What it means
The bank 1 sensor 2 NOx sensor heater control circuit is below the expected electrical range. The code does not by itself identify the cause.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The heater control circuit warms the bank 1 sensor 2 NOx sensing element so it can reach operating conditions. This code sets when the module detects the heater circuit voltage or control signal below its expected range; the code alone does not identify the cause.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Check freeze-frame and related heater codes to establish when the bank 1 sensor 2 heater circuit went low.
- Inspect the heater wiring for chafing through insulation or contact with ground near the exhaust.
- Check the connector for corrosion, moisture, damaged pins, or high-resistance connections.
- Monitor heater command and circuit data with a scan tool, following the vehicle's service procedure.
- Test heater supply, ground, and control wiring for a short to ground or excessive resistance against the manufacturer's specification.
Common fixes
- Repair insulation damage causing a heater wire to contact ground.
- Clean or repair corroded connector terminals and restore a sound connection.
- Repair a damaged heater control or supply wire.
- Replace the sensor if its heater circuit tests faulty after the harness is verified.
Can I keep driving?
Cautious driving is usually possible if the engine runs normally, but the downstream NOx sensor may not warm correctly and emissions monitoring may be affected. Respond promptly to any DEF warning or start countdown.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.