P0043 Code – HO2S Heater Control Circuit Low (Bank 1 Sensor 3)
P0043 is an OBD-II generic diagnostic trouble code indicating that the Engine Control Module (ECM) has detected a low voltage condition in the heater control circuit of the Heated Oxygen Sensor (HO2S) at Bank 1 Sensor 3.
Code Meaning
P0043 – HO2S Heater Control Circuit Low (Bank 1 Sensor 3)
Symptoms
- Check Engine Light (MIL) illuminated.
- Delayed oxygen sensor warm-up.
- Reduced fuel economy.
- Higher exhaust emissions.
- Usually no noticeable drivability problems.
Possible Causes
- Faulty Bank 1 Sensor 3 oxygen sensor heater.
- Open circuit in the heater wiring.
- Short to ground in the heater circuit.
- Blown heater fuse.
- Loose or corroded connector.
- Faulty ECM (rare).
Sensor Location
Bank 1 Sensor 3 is located after the catalytic converter(s) on the cylinder bank containing cylinder number 1. This sensor is found only on vehicles equipped with a third oxygen sensor on Bank 1.
How to Diagnose
- Confirm P0043 with an OBD-II scan tool.
- Inspect the sensor connector and wiring.
- Check the heater fuse and power supply.
- Measure heater resistance using a digital multimeter.
- Repair damaged wiring or replace the oxygen sensor if necessary.
Common Repairs
- Replace Bank 1 Sensor 3 oxygen sensor.
- Repair open or shorted heater wiring.
- Replace a blown fuse.
- Clean or replace damaged electrical connectors.
- Clear the DTC and verify the repair with a road test.
Can You Drive with P0043?
Yes. The vehicle can usually be driven safely, but emissions and fuel efficiency may be affected until the problem is repaired.
Related OBD-II Codes
- P0042 – HO2S Heater Control Circuit (Bank 1 Sensor 3)
- P0044 – HO2S Heater Control Circuit High (Bank 1 Sensor 3)
- P0141 – O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
- P0161 – O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)