DTC P0155: Ho2S Heater Circuit - Bank 2, Sensor 1: Description

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.

Heated Oxygen Sensors (HO2S) are used to minimize the amount of time required for Closed Loop fuel control operation and to allow accurate catalyst monitoring. The Oxygen Sensor (O2S) heater greatly decreases the amount of time required for fuel control sensors to become active. An O2S heater is also required by catalyst monitor HO2S to maintain a sufficiently high temperature which allows accurate exhaust oxygen content readings further from the engine. The Powertrain Control Module (PCM) will run the heater test only after a cold start, and only once during an ignition cycle. A cold start is determined by Engine Coolant Temperature (ECT) and the Intake Air Temperature (IAT) at the time of start-up. When the engine is started the PCM will monitor the HO2S voltage. When the HO2S voltage indicates a sufficiently active sensor, the PCM looks at how much time has elapsed since start-up. If the PCM determines that too much time was required for the HO2S to become active, this DTC will set. The time the HO2S takes in order to reach operating temperature is based on the ECT at start-up and the average Mass Airflow (MAF) since start-up. The higher average airflow, or the higher start-up ECT equals a shorter time to HO2S activity.