Code Definition

P1166 — Heated Oxygen Sensor 2 bank2 voltage low

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

About P1166

P1166 is a manufacturer-specific powertrain diagnostic trouble code recorded for Infiniti vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1166 is stored, the module has detected a signal or supply voltage lower than the expected operating range; 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.

P1166 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

The heated oxygen sensor 2 on bank 2 is the rear, post catalyst sensor on the bank that does not contain cylinder number one. The Engine Control Module (ECM) uses it mainly to monitor catalytic converter efficiency by comparing its slow, steady signal against the front sensor switching. DTC P1166 sets when the ECM detects that this rear sensor signal is biased low, holding toward the lean end of its range. The cause may be a real lean exhaust condition, a contaminated or aged rear sensor, an exhaust leak near the sensor, or a signal or heater circuit fault. The malfunction indicator lamp will ...

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