What does it take to make the EPA OBD II catalyst monitor complete?

[pkincy]

I have the GM drive cycle and have used it several times, but I can not get the catalyst monitor to complete. Exactly what does it take to complete the catalyst monitor. No other trouble codes have been set.

This is a 98 Camaro.

Perry

[joecar]

Drive at freeway speeds (55+ mph) for say 20 minutes, then come down to idle for a few minutes.

[pkincy]

Thank you. What is it monitoring? Front O2 vs O2s behind the cat? Does it do this by simply measuring front O2 frequencies vs rear O2 frequencies?

[joecar]

When the conditions are met (freeway speeds followed by closed loop idling), the PCM manipulates the AFR (or EQIVRATIO) and times the response of the rear O2 wrt the front O2... if the response is too soon then it triggers P0420/P0430... if the response is sufficiently delayed then no DTC is triggered.

[joecar]

In this image, bank 1 cat is failing, look closely at EQIVRATIO, AFR, HO2S11, HO2S12, the bookmark is when P0420 triggered:

[pkincy]

Thank you, then I should have no problem completing the catalyst monitor as no codes are being set.