Circuit Description

Powertrain Control Module (PCM) continuously monitors Oxygen Sensor 1 (O2S 1) activity for 100 seconds. During the monitor period, PCM counts number of times O2S 1 switches from rich to lean and from lean to rich. PCM then adds amount of time O2S 1 took to complete all switches. With this information, an average time for all switches can be determined. Whenever average time to switch is too slow, a DTC P0133 will set.

Conditions for setting this DTC are as follows:

• Average O2S 1 response times are greater than 249 milliseconds for rich to lean or lean to rich sweeps.
• Engine speed is 1825-2600 RPM.
• TP sensor angle is 8-20 percent.
• Ratio of response times is greater than 3.5 or less than .4.
• Purge learned memory is greater than 191.
• No presence of Codes: P0106-P0108, P0112, P0113, P0117, P0118, P0121-P0123, P0300-P0304, P0506, P0507, P1171, P1406, P1441.
• Evaporative emission control system is commanded open for greater than 50 percent Pulse Width Modulated (PWM).