ok Imnew to this site so dont bag to hard if i screw up, not sure if there is a thread on this subject already but i have an intermittent (not sure if spelled that right) check engine light but every time i go to plug in a scanner to my vehicle it shuts off the scanner as soon as i hit the scan button. If anyone can help me with both the scanner issue and my intermittent CEL or direct me where to go that would be great....BTW I have 99 blazer zr2. I also have no symptoms when the light comes on. and whether it is on or not my car rauns like *** over aabout 90 degrees whether the ac is on or not.

 

Sounds like the ECU is going bad. Thats a pretty clear symptom that the computer is caput or the wiring from the OBD plugin to the computer.