P0042 low

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.

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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.