P0042 Code – HO2S Heater Control Circuit (Bank 1 Sensor 3)
P0042 is an OBD-II generic diagnostic trouble code indicating that the Engine Control Module (ECM) has detected a malfunction in the heater control circuit of the Heated Oxygen Sensor (HO2S) located at Bank 1 Sensor 3.
Code Meaning
P0042 – HO2S Heater Control Circuit (Bank 1 Sensor 3)
Symptoms
- Check Engine Light (MIL) illuminated.
- Increased exhaust emissions.
- Reduced fuel economy.
- Delayed oxygen sensor warm-up.
- Usually no noticeable drivability problems.
Possible Causes
- Faulty Bank 1 Sensor 3 oxygen sensor heater.
- Open or shorted heater circuit wiring.
- Blown heater fuse.
- Loose or corroded electrical connector.
- Faulty ECM (rare).
Sensor Location
Bank 1 Sensor 3 is the third oxygen sensor on the bank containing cylinder number 1. It is typically installed after the second catalytic converter on vehicles equipped with three oxygen sensors on one bank.
How to Diagnose
- Confirm the DTC with an OBD-II scanner.
- Inspect the oxygen sensor connector and wiring.
- Check the heater fuse and power supply.
- Measure heater element resistance with a digital multimeter.
- Replace the sensor if the heater element is defective.
Common Repairs
- Replace Bank 1 Sensor 3 oxygen sensor.
- Repair damaged heater circuit wiring.
- Replace a blown fuse.
- Clean or replace corroded connectors.
- Clear the code and perform a road test.
Can You Drive with P0042?
Yes, but prolonged driving may increase emissions and reduce fuel efficiency. The fault should be repaired as soon as practical.
Related OBD-II Codes
- P0043 – HO2S Heater Control Circuit Low (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)