O2 Sensor Circuit (Bank 1, Sensor 3)
The P0142 code means the vehicle's onboard diagnostic system has detected: O2 Sensor Circuit (Bank 1, Sensor 3). This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $50-$200
Test O2 sensor voltage (should fluctuate 0.1-0.9V). Do not replace a $150 sensor without confirming it is actually bad first.
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Shows real-time O2 sensor readings on your phone. See if the sensor is lazy, stuck, or actually working before spending money.
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Common Symptoms
- Check Engine Light on
- Emissions issue
- Minor fuel economy change
Probable Causes (Ranked by Likelihood)
- Failed third O2 sensor (after second catalyst, if equipped) Very High
- Wiring damage to third sensor High
- Sensor heater failure Moderate
Step-by-Step Diagnostic Procedure
-
Locate the Bank 1 Sensor 3 position (typically after the second catalytic converter on longer exhaust systems).
-
Test sensor voltage, heater resistance, and wiring continuity.
-
Replace if confirmed faulty.
Frequently Asked Questions
Does my car have three O2 sensors on Bank 1?
Only certain vehicle configurations with two catalytic converters in series on one bank use a Sensor 3 position. Most cars only have Sensor 1 (upstream) and Sensor 2 (downstream).
Sources
This page is built from documented references. Verify against your own service info before repair work.
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