Code Definition

P1143 — Heated Oxygen Sensor 1 bank 1 voltage low

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Nissan

About P1143

P1143 is a manufacturer-specific powertrain diagnostic trouble code recorded for Nissan vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1143 is stored, the module has detected a signal or supply voltage lower than the expected operating range; a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1143 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

Heated oxygen sensor 1 is the front, pre catalyst oxygen sensor on bank 1, mounted in the exhaust front tube where it compares oxygen in the exhaust against outside air. Its zirconia element generates roughly 1V under rich conditions falling toward 0V under lean conditions, and the ECM uses this signal to trim the injection pulse and hold the air fuel ratio near stoichiometric. DTC P1143 is a lean shift monitoring fault, set when the sensor signal stays biased low, meaning its voltage does not swing rich enough or its switching point has shifted lean. This is usually caused by an aged or conta...

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