Code Definition

P0143 — O2 Sensor Circuit Low Voltage (Bank 1 Sensor 3)

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0143

P0143 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0143 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.

Because P0143 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0143 fault code is set when the Engine Control Module (ECM) detects a lower than expected voltage output from the oxygen sensor located in Bank 1, Sensor 3. This sensor is typically situated downstream in the exhaust system and may be associated with vehicles having multiple catalytic converters or advanced emission systems. A low voltage signal from this sensor can suggest that the oxygen level in the exhaust is higher than expected, indicative of a lean air-fuel mixture or an issue with the sensor itself. This condition can be caused by a faulty oxygen sensor, problems in the wiring or ...

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