What it means
The ECU detects an abnormally low voltage from the third O2 sensor on bank 1. Indicates persistently lean exhaust, an open sensor or wiring shorted to ground.
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 on vehicles that use one. P0144 sets when its signal stays lower than the module expects; that can reflect lean exhaust, a signal wire shorted to ground, or a failed sensor.
Common causes
Most likely first.
- Lean exhaust (vacuum leak, low fuel pressure)
- Signal wire shorted to ground
- O2 sensor failed
Symptoms
- Check engine light on
- Failed emissions test
How to diagnose it
- Review freeze-frame data and live Sensor 3 readings, and check for lean-mixture, misfire, or other oxygen-sensor codes.
- Inspect the Bank 1 Sensor 3 connector and harness for chafing, melted insulation, corrosion, or a wire contacting ground.
- Check for exhaust leaks and engine air leaks that could make the exhaust genuinely lean at Sensor 3.
- Test the signal circuit for a short to ground and verify sensor power and heater operation using the manufacturer's procedure.
- If wiring and exhaust integrity are sound, investigate fuel delivery and test the Sensor 3 response before replacing the sensor.
Common fixes
- Repair a signal wire short to ground or damaged connector at Bank 1 Sensor 3.
- Repair an exhaust leak or intake air leak confirmed by testing.
- Correct a verified fuel-delivery problem causing lean exhaust.
- Replace Bank 1 Sensor 3 if its signal remains low despite a sound circuit and normal exhaust mixture.
Can I keep driving?
If the engine runs normally, limited driving is generally possible, but have the low signal diagnosed soon because a real lean condition can raise combustion temperatures or cause poor running. Stop if the engine misfires, loses power, 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.