Code Definition

P1165 — Primary Heated Oxygen Sensor (#1) circuit

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

About P1165

P1165 is a manufacturer-specific powertrain diagnostic trouble code recorded for Honda vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1165 is stored, the module has detected 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.

P1165 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

DTC P1165 is a Honda specific code for a range or performance fault in the primary, or upstream, Air Fuel Ratio sensor circuit, the wideband sensor Honda refers to as the Primary Heated Oxygen Sensor. This sensor reports actual air fuel ratio to the Powertrain Control Module (PCM) as a lambda or equivalence ratio value rather than a simple switching voltage. P1165 sets when that reported air fuel ratio stays outside the window the PCM expects for the current load and fuelling, suggesting the sensor has drifted, aged, or is being skewed by an exhaust or mixture fault. The driver may notice slig...

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