Check Engine Light

[Keith Moffett]

My check engine light comes on randomly.  There seems no specific interval or cause.  Once it comes on it remains on until I stop and cycle the engine off and on. After that I am good for a time but it comes back in a couple hours.
This started just before an oil change but continues after.  All filters are new but the Air.  The serpentine belt is good and the fluids are too. 
The dash gauge and Aladdin each show normal temps within 2 or 3 degrees.
I have noticed the dash temp gauge doesn’t drop to zero when the motor is off.  Perhaps a temp sensor?
Many thanks

[Steve Huber Co-Admin]

Keith,
I doubt the dash temp sensor is the cause as, in general, the ECU doesn't use the dash gauge sensors as inputs. I suspect an intermittent sensor but until it fails or the ECU throws a code, it will be pretty tough to ID it. Mine started doing something similar after my last oil change. Check Engine comes on for a bit on start up. Interestingly it started after an oil change when I switched from Fleetgard to CAT filters. Sure it's not related. Engine runs flawlessly so no wories.
Steve

[Keith Moffett]

Thanks Steve
BTW, We just had CAT run a full diagnostic report last fall.  The only fault found involved injector pressure and it was not critical.  Perhaps 500 miles ago.  The filter changed was CAT as is the new one.