Ken, there could be some meaning behind engine light on and off. Yes it does sound like event code is taking place and when event has past light will go off. Many times at first light will not stay on long enough to
set a event code. The ECM monitors engine operating conditions such as low oil pressure or high coolant temperature. fuel filter restriction etc. If operating condition exceeds the normal condition, a event code is generated. the event will remain active untill the condition returns back to normal. When a output sensor
voltage is between 4.2 volts and 4.8 volts, the ECM will generate an event code ( an or light will come on
than go off) if happening come more and more a event code will be active and a code should be generated. Dave AthertonRetired Cat Mechanic