What it means
The control module monitors the oxygen sensor circuit for bank 1, sensor 3, and sets this code when it detects an electrical fault in that circuit. The code does not by itself identify whether the sensor or its wiring is at fault.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 3 refers to the third oxygen sensor assigned to the bank 1 exhaust path, where that sensor is fitted; it may be downstream of more than one catalyst. P0142 identifies an electrical fault in that sensor circuit, but does not by itself distinguish a sensor fault from a wiring or heater-circuit problem.
Common causes
Most likely first.
- Sensor heater element open
- Heater fuse blown
- Heater wiring or connector fault
Symptoms
- Check engine light on after several drive cycles
- Slightly increased fuel consumption during cold start
- Delayed entry into closed-loop fuel control
- Failed emissions inspection (lambda readiness)
How to diagnose it
- Confirm the vehicle has a Bank 1 Sensor 3 and use a scan tool to review freeze-frame data and related oxygen-sensor codes.
- Locate Sensor 3 using vehicle service information, then inspect its connector and harness for heat damage, corrosion, loose pins, or chafing.
- Check the relevant oxygen-sensor heater fuse and supply, since a heater fault is among the reported causes of this circuit code.
- Test the Sensor 3 heater and signal wiring for opens, shorts, and poor connections using the manufacturer's procedure.
- If the wiring and fuse are sound, compare Sensor 3 live data with other exhaust sensors and test the sensor before replacing it.
Common fixes
- Repair a damaged or corroded Bank 1 Sensor 3 connector or harness.
- Replace a blown heater fuse after correcting the cause.
- Replace Bank 1 Sensor 3 if its heater element or sensor circuit fails testing.
- Repair a confirmed circuit supply or control fault.
Can I keep driving?
If the engine runs normally, the car is generally drivable for a short time, but the warning can prevent emissions readiness and lead to inspection failure. Reduce driving and seek prompt diagnosis if it develops rough running, hesitation, or other warning lights.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.