What it means
The ECU detects an abnormally high voltage from the third O2 sensor on bank 1. Indicates persistently rich exhaust, a shorted sensor or wiring shorted to a voltage source.
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 is the third oxygen sensor in the bank 1 exhaust path where fitted. P0145 sets when its signal stays higher than the module expects, which can result from genuinely rich exhaust, a signal wire shorted to voltage, or a failed sensor.
Common causes
Most likely first.
- Rich exhaust (leaking injector, high fuel pressure)
- Signal wire shorted to voltage
- O2 sensor failed
Symptoms
- Check engine light on
- Failed emissions test
How to diagnose it
- Record freeze-frame data and compare live Sensor 3 readings with fuel-trim data and any rich-running or misfire codes.
- Inspect the Bank 1 Sensor 3 connector and wiring for melted insulation, shorts to a power wire, corrosion, or poor connections.
- Check for signs of rich operation and investigate possible causes such as a leaking injector or excessive fuel pressure.
- Test the Sensor 3 signal circuit for a short to voltage and verify its grounds and heater circuit using the manufacturer's procedure.
- If the circuit and mixture are normal, test the sensor response before replacing Bank 1 Sensor 3.
Common fixes
- Repair a signal wire short to voltage or damaged Sensor 3 connector.
- Correct a confirmed rich-running cause, such as a leaking injector or fuel-pressure control fault.
- Repair a wiring or ground fault found during circuit testing.
- Replace Bank 1 Sensor 3 if it fails testing with a sound circuit and normal mixture.
Can I keep driving?
If there are no drivability symptoms, a short trip for diagnosis is generally reasonable, but persistent rich running can increase emissions and damage the catalytic converter. Stop driving if the engine runs badly, fuel odor is strong, or the warning light flashes.
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.