Catalyst Monitor

Perform the following:

Engine coolant temp above 170°F.
Accumulated open throttle time of 3:00 minutes.
Vehicle speed above 20 MPH
TP Sensor is open for 4:00 minutes (A/T) or 5:00 minutes (M/T).
MAP range during monitor: 14.60" to 18.20".
The RPM range during monitor: 1500 RPM to 2000 RPM.
Time spent in MAP and RPM ranges should be more than 3.9 seconds.
No Limp-In or OBD-II Monitor faults present.

NOTE: If the vehicle speed drops below 20 MPH or the throttle is closed, the timer counts back down until the vehicle speed is above 20 MPH, then the counter resumes counting up again.

The PCM begins the monitor. The PCM starts a timer and counts the Upstream O2S switches and counts the Downstream O2S switches until 20 seconds is reached. After 20 seconds is reached, the PCM divides the Downstream O2S switches by the Upstream O2S switches to determine the switching frequency. If it is less than the calibrated amount, the catalyst monitor passes. If it is more than the calibrated amount, the test increments a count of 1 and the test is done again. A count of 2 will cause the monitor to fail 1 trip and store Freeze Frame Data.