Theory Of Operation

The Powertrain Control Module (PCM) monitors the Injector timing controls and the time it takes for them to enter closed loop by using a system called Zero Fuel Control (ZFC) Diagnostics. There are two separate timers to monitor ZFC, a short-term timer and a long-term timer. The short-term timer measures the length of time it takes to enter closed loop compared to the ZFC diagnostic last run. The long-term timer runs any time it is possible for the closed loop ZFC to be active. The short term timer runs under more stringent conditions when it is likely that the closed loop ZFC will be active.