Cadillac Repair: running rough, diagnostic scanner, autozone

Question
2004 CTS 3.6 started running rough at idle and slow speeds runs fine at 40mph+. Engine light on. I would like to try to fix without taking to shop. Any suggestions to check first.

Answer
Did you resolve your problem ?.

You need a diagnostic scanner in order to retrieve the FAULT CODES from the computers. Autozone will retrieve the codes for you and ask them to write down the:

CODES:

and which codes are HISTORY:

and which codes are CURRENT:

Then ask them to ERASE (CLEAR) them. Once the light comes back ON. Let me know.