Hi my check engine light goes on out of the blue. I have had my mechanic do a tune up, change the spark plugs. It goes off for a few days and then back on. My oil pressure stays the same.,no knocking noise . Is it ok to drive

So were do I start the hunt for the problem

Radiator Coolant and Oil levels are good. Dash Panel switches seem to be working (can hear the main on/off switch working). Fuses and Relays have been checked. Could it be that the Blower Motor Resistor is going bad? Shouldn't the Blower motor come on simply by turning the key to the ON (not starting or running) position? When the Blower Motor does work, it works great. Can't seem to put a finger on this problem. Hopefully someone has the answer! Patiently sweating it out while waiting..

The van starts back up after an hour or so, but only runs a few mins, then same thing again. "no bus" shows up where mileage should be as van is shutting down.

floor or the dash vents. I have checked for vacuum leaks. did not find anything

while driving at steady speed with ac on and all things working as they should. suddenly the defroster comes on still blowing cold, a couple of minutes later the floor vents open still blowing cold, a couple of minutes later the dash vents open still blowing cold. this continues as long as you drive.

I have looked through the owners manual and can't find it anywhere. However I can search for the part and find it but no diagram anywhere on the web showing where it is located.

Also.....9/10 times, I have to wait for gauges to come on for engine to start. If not, I have to disconnect and reconnect the wire bundle coming from the neg. side of battery.. ECM?