What it means
The heater control circuit for the Bank 1 Sensor 2 heated oxygen sensor is reporting voltage below the expected range.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 2 is the heated oxygen sensor after the catalytic converter on the side of the engine containing cylinder 1. Its heater brings the sensor up to operating temperature, and the module sets P0037 when it detects the heater control circuit voltage is lower than expected.
Common causes
Most likely first.
- Heater wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine light on
- Oxygen-sensor heater may warm slowly
- Fuel economy may decrease
- Emissions may increase
How to diagnose it
- Use a scan tool to record freeze-frame data and check heater command and sensor readings, since the fault may be more likely while the exhaust and sensor are cold.
- Inspect the Bank 1 Sensor 2 connector and nearby harness for corrosion, damaged insulation, or contact with the exhaust.
- Check the heater circuit wiring for a short to ground, especially where the harness could have chafed.
- With the circuit safely isolated as specified by the manufacturer, test the heater wiring and connector for continuity and unwanted connection to ground.
- Test the sensor heater and its control circuit against the manufacturer's specification to distinguish a wiring fault from a failed heater or control issue.
Common fixes
- Repair chafed heater wiring and protect it from the exhaust or other edges.
- Clean or repair corroded Bank 1 Sensor 2 connector terminals.
- Replace the Bank 1 Sensor 2 oxygen sensor if its heater fails testing.
- Repair the heater control circuit if wiring tests identify a short to ground.
Can I keep driving?
Usually the vehicle can be driven gently if it runs normally, but arrange repair soon because the downstream sensor may warm slowly and emissions can rise. Stop driving if the engine begins running poorly or another warning indicates a more serious problem.
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.