Circuit Description

This diagnostic is performed when converter light off is enabled or when the converter light off is disabled due to idle instability. Converter light off refers to the transition of the converter from a cold start condition to the state when the converter has warmed up enough to begin catalytic conversion (Closed Loop). In order to help the converter heat up as quickly as possible and reduce emissions, the spark retard is modified under cold start conditions. This diagnostic monitors the enable and disable conditions of converter light off spark retard. The fail/pass determination is based on the monitoring for multiple key cycles and fueling cycles.