What's up all. Will a diagnostic scan such as the freebie at Autozone provide any insight if your SES light ISN'T on? My truck is running like chit (seems to be running on 6 or 7 cylinders at times) but no light. I don't know if the scan can tell a dirty injector, bad coil, etc if a code isn't thrown. Any insight appreciated.

BD

 

The light only comes on under certain conditions. If a problem has occured X number of times or if the issue is X serious.

Often there are codes stored even if the light isnt on. THe light is designed MOSTLY as a emissions warning. So if your engine is running badly BUT is not spewing emissions then the light may not get tripped

Doug