P1143 Possible Causes
- Faulty heated oxygen sensor upstream, bank 1
- Intake air leaks
- Heated oxygen sensor upstream circuit bank 1 is open or shorted
- Poor electrical connection in the heated oxygen sensor upstream circuit, bank 1
- Fuel pressure
- Injectors
How to Fix Code P1143?
Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
- Engine light on (or engine service warning light soon)
P1143 Meaning
The heated oxygen sensor 1 is placed in the upstream pipe. It detects the amount of oxygen in the exhaust gases compared to the outside air. The heated oxygen sensor 1 has a closed-end zirconia ceramic tube. Zirconia generates a voltage from about 1 V under richer conditions to 0 V under leaner conditions. The heated oxygen sensor 1 signal is sent to the engine control module (ECM). The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the abrupt change from 1V to 0V.