Engine Speed And Spark Timing Monitor

The system monitor and component monitor share the same entry conditions and monitor flow. During the first 15 seconds of a cold start, the monitor checks the entry conditions, counts time in idle, observes catalyst temperature, calculates the average difference between desired and actual engine speed, and calculates the average difference between desired and commanded spark.

If the expected change in catalyst temperature is large enough, the monitor then begins a waiting period of 300 seconds after engine start. This waiting period allows time to diagnose other components and systems that affect the validity of the test. During this waiting period, there are no constraints on drive cycle and the monitor cannot be disabled without turning OFF the ignition.

If the system monitor result falls below its threshold and all of the component monitor results are below their respective thresholds, the monitor determines if the idle time was sufficient. If the idle time was sufficient the test is considered to be a pass and the monitor is complete. If idle time was not sufficient, the monitor will not make a pass call and does not complete. This prevents tip-ins from resulting in false passes.