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, DTC P0133 will set.

For duplication of DTC, ensure:

• DTCs P0131, P0132 or P0135 are not set.
• No active fuel trim, fuel injector circuit, misfire, EVAP, EGR, AIR, TP, IAT, MAP, ECT, CKP or MAF sensor DTCs are present.
• System voltage is greater than 9 volts.
• System is in closed loop.
• Engine has been running for at least 3.3 seconds.
• ECT is greater than 167°F (75°C).
• Engine speed is 1000-3000 RPM.
• MAF is 15-40 grams per second.