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 bank containing cylinder 1. The module monitors the electrical circuit that controls this sensor's heater. P0043 sets when the Bank 1 Sensor 2 heater circuit voltage is lower than expected, which can result from a short to ground or excessive resistance.
Common causes
Most likely first.
- Heater wiring 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
- Review freeze-frame data and related codes to establish when the Bank 1 Sensor 2 heater circuit went low.
- Inspect the Bank 1 Sensor 2 connector and harness for chafing, heat damage, moisture, corrosion, or pins contacting ground.
- Check the heater circuit fuse and supply, then compare circuit readings with the manufacturer's specification.
- Test the heater control wire for a short to ground and check connector contact condition for excessive resistance.
- Test the Bank 1 Sensor 2 heater element and, if those checks pass, verify the module's heater control output using the manufacturer's procedure.
Common fixes
- Repair chafed Bank 1 Sensor 2 heater wiring that is shorted to ground.
- Clean or repair corroded connector terminals and restore proper pin contact.
- Replace the Bank 1 Sensor 2 sensor if its heater fails the specified test.
- Repair a verified fault in the heater supply or module-controlled circuit.
Can I keep driving?
If the engine runs normally, limited gentle driving is generally possible, but the heater fault can delay sensor operation and raise emissions. Avoid towing or hard acceleration if performance becomes abnormal, and address the circuit fault promptly.
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.