Possible causes
– Faulty Front Heated Oxygen Sensor Bank 1
– Intake air leaks
– Front Heated Oxygen Sensor Bank 1 harness is open or shorted
– Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
– Fuel pressure
– Injectors
– Intake air leaks
– Front Heated Oxygen Sensor Bank 1 harness is open or shorted
– Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
– Fuel pressure
– Injectors
Tech notes
If there are no intake air leaks, the most likely cause of the P1143 code is the front O2 sensor bank 1.
When is the code detected?
The maximum and minimum voltage from the sensor are not reached to the specified voltages.
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P1143 NISSAN Description
The heated oxygen sensor 1 is placed into the front tube. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.