Heated Oxygen Sensor Heater Control Circuit (Bank 1, Sensor 3)
The P0042 code means the vehicle's onboard diagnostic system has detected: Heated Oxygen Sensor Heater Control Circuit (Bank 1, Sensor 3). This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $100 - $300 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Slightly reduced fuel economy
- Extended warm-up time for sensor readings
- Possible emissions test failure
Probable Causes (Ranked by Likelihood)
- Faulty O2 sensor heater element in Sensor 3 Very High
- Blown fuse for O2 sensor heater circuit High
- Open or short in heater circuit wiring Moderate
- ECM/PCM heater control driver failure Low
Step-by-Step Diagnostic Procedure
-
Confirm P0042 with scan tool and identify Bank 1 Sensor 3 location
-
Check the O2 sensor heater fuse in the fuse box
-
Measure heater circuit resistance at the sensor connector
-
Inspect wiring from ECM to the sensor for opens or shorts
Frequently Asked Questions
What does P0042 mean?
P0042 indicates a malfunction in the heater control circuit for the Bank 1 Sensor 3 oxygen sensor, which is typically located after the catalytic converter.
Where is Bank 1 Sensor 3?
Bank 1 Sensor 3 is the oxygen sensor positioned after the second catalytic converter on Bank 1. Not all vehicles have a Sensor 3, so this code is most common on V6 or V8 engines.
Can I drive with P0042?
Yes, you can drive normally. The heater circuit issue mainly affects cold-start emissions performance and may cause a slight decrease in fuel economy.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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