If the ECU fuse is not pulled, hence it is not reset then why does the check engine light go off for the first few miles. I would think if you have to reset the ECU to get rid of the alarm that the check engine light would come on as soon as you restarted the vehicle.
Alright ejohn, lemme see if we can clear this up…
If the warning lamp lights while the vehicle is operating, the ECU has sensed a system fault… may be either loss of signal or signal out-of-range, either high or low, and when the CHECK ENGINE lamp is lit, the ECU has entered the default or fail-safe mode in which fixed values are substituted for the faulty or missing signal.
Any recurring fault code(s) will be set in memory and the ECU will send a "coast is clear" signal (CEL off) to further monitor any other fault that may arise... and for this reason, troubleshooting should be based on the presence of stored code(s).
I thought the ECU in this year vehicle did not require resetting as it is reset each time the vehicle is turned off.
Yes, the ECU only requires resetting when clearing codes (procedures below).
Stored codes are removed from memory by removing the power to the ECU, while disconnecting the battery will clear/reset the memory, this is not the recommended procedure. The memory should be cleared after the ignition is switched OFF by removing the appropriate fuse (7.5A Alt. Sense Fuse; underhood fuse and relay panel) for at least 10 seconds.
Hope this helps.