Code Definition

P1155 — Air/Fuel Sensor Heater circuit

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

About P1155

P1155 is a manufacturer-specific powertrain diagnostic trouble code recorded for Toyota vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1155 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.

P1155 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

This DTC sets when the Engine Control Module (ECM) detects a malfunction in the heater circuit of the air fuel ratio sensor located on Bank 2 Sensor 1. The heater brings the sensor element up to operating temperature quickly so closed loop fuel control can begin on that bank, and the ECM monitors the heater current and warm up behaviour to confirm correct operation. If the heater circuit shows an open, a short, or insufficient current draw, the ECM logs this fault. The main effect is delayed entry into closed loop on Bank 2, which can raise emissions and cause slightly rough cold running with ...

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