P0143 code meaning
O2 Sensor Circuit Low Voltage Bank 1 Sensor 3
Powertrain system Generic code P01xx codes Check engine light
What P0143 means
Sensor 3 is a third oxygen sensor on bank 1, behind a second converter or converter brick. It only exists on some vehicles – documented for Jaguar Land Rover's 3.0 V6 supercharged (2013–2016, where sensor 2 is 'mid-cat' and sensor 3 'post-cat') and Ford systems that monitor part of the converter volume. P0143 means the signal of sensor 3 stays below its lower limit – typically a short to ground, or on some systems an open circuit. Jaguar Land Rover assigns it to the post-cat sensor; Ford applies the same pull-up resistance check as for sensor 2 (open above 1 MΩ, short below 10 Ω). Code-specific thresholds for sensor 3 are not published. When it fails, the control module stops the downstream trim and cannot evaluate the converter; there is no limp mode.
P0143 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.2 to 1 hours
- Clears after repairAfter a drive cycle
Symptoms of P0143
- Check engine light on (usually after two drive cycles)
- Catalyst monitor readiness not set
- Usually no noticeable change in driving
Common causes of P0143
- Most likelySignal wire shorted to ground or melted against the exhaust
- Most likelySensor faulty (cracked element, thermal shock from water)
- PossibleSignal circuit open (counts as low on Ford)
- PossibleExhaust leak ahead of the sensor (lean reading)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor bank1 sensor3Oxygen sensor wiringCatalytic converter
What each part of P0143 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 43 | The exact fault in that area. |
What to do next
- Note P0143 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0143
What does P0143 mean?
P0143 means "O2 Sensor Circuit Low Voltage Bank 1 Sensor 3". Sensor 3 is a third oxygen sensor on bank 1, behind a second converter or converter brick. It is a generic code, so it means the same on every make.
Is it safe to drive with P0143?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0143 fail an emissions test?
Yes, it can. P0143 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0143 to fix?
Difficulty: easy. A typical repair takes 0.2 to 1 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0143 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.