Code Definition

P0155 — O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

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

About P0155

P0155 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 P0155 is stored, the module has detected 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 P0155 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 P0155 fault code is set when the Engine Control Module (ECM) detects a malfunction in the heater circuit of the oxygen sensor located in Bank 2, Sensor 1. This sensor is typically situated upstream in the exhaust system, before the catalytic converter, on the side of the engine known as Bank 2. Many oxygen sensors include an integrated heater that helps bring the sensor up to its optimal operating temperature quickly, which is crucial for accurate readings. A malfunction in the heater circuit could be due to a defective heater element within the sensor, issues with the wiring or connectors...

Join TaT to view the complete code information and diagnostic details.

Quick Facts