Circuit Description

The Engine Control Module (ECM) continuously monitors the Oxygen sensor 1 (O2S1) activity for 100 seconds. During the monitor period, the ECM counts the number of times that the O2S1 switches from rich to lean and from lean to rich and adds the amount of time it took to complete all switches. With this information, an average time for all switches can be determined. If the average time to switch is too out of specification, a DTC P0133 will set.

If the O2S1 pigtail wiring, connector, or terminal is damaged, the entire O2S1 assembly must be replaced. Do not attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained byway of the O2S1 wire(s). Any attempt to repair the wires, connector, or terminals could result in the obstruction of the air reference and degrade O2S1 performance.