Conditions For Setting DTC
WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
The AF ECM monitors an HO2S signal voltage that did not leave the cold sensor bias voltage range 0.30 volt (300 mV) to 0.60 volt (600 mV) in an acceptable amount of time. The time varies from 50 seconds to 110 seconds based upon mass air flow.