P0142
O2 Sensor Circuit Bank 1 Sensor 3
Oxygen sensor
Generic OBD-II
Medium
What it means
P0142 means a circuit fault with the bank 1, sensor 3 oxygen sensor — the third (rear-most) sensor in the exhaust on that bank. It's a downstream monitoring sensor, so the code mainly affects emissions monitoring rather than drivability. The usual cause is a failed sensor or a wiring/connector problem.
Medium
Can I keep driving? Safe to drive — sensor 3 is a post-catalyst monitoring sensor, so the fault mainly affects emissions monitoring rather than how the engine runs.
Common symptoms
What you'll notice
- Check-engine light on (often the only sign)
- May fail an emissions/smog test
- Slightly worse fuel economy in some cases
Common causes
Most likely first
- Failed bank 1 sensor 3 oxygen sensor (most common)Likely
- Corroded or damaged sensor connectorCommon
- Chafed, shorted, or open wiring in the sensor circuitCommon
- Exhaust leak near the sensor upsetting its readingsLess often
- Faulty ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame and watch the bank 1 sensor 3 signal live to confirm it's flat, stuck, or out of range.
- Inspect the sensor's connector and wiring for corrosion, chafing, or a short.
- Check for exhaust leaks upstream of the sensor that could skew its reading.
- Replace the bank 1 sensor 3 oxygen sensor if the wiring is good, then clear and re-test.
- Only suspect the ECM after the sensor and wiring are confirmed good.
FAQ
Quick answers
Is it safe to drive with P0142?+
Yes. This downstream sensor is used mainly to monitor the catalytic converter and emissions, so the car drives normally; fix it to pass inspection.
Can I just clear P0142?+
It returns if the sensor or its wiring is still faulty. Repair or replace the sensor first, then clear the code.
Related codes
Often seen with P0142
Read & clear P0142 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX