[Andyb119]

I fully agree that CELs are only a starting point. Unfortunately, my experience with dealer's service departments is often no better than the the pepboys approach. Anytime multiple codes appear you should be suspect that they are identifying the culprit. I have had more than a few experiences where the dealer mechanics didn't know as much as I did about the car or the problem. For example, I had a mechanic tell me he had to remove the intake manifold to replace the spark plug wires on a 2.5l cougar. I have asked for tests specified in the ford service manual, only to have the service manager tell me they didn't know what I was talking about and the only available diagnosis was an extremely expensive disassembly. I have sent my wife to have a warranted item fixed only for them to fix a half dozen other things before they finally did what I asked them to do in the first place. These were different dealerships by the way.

I have also found a dealership mechanic who knew his particular brand of vehicles like the back of his hand and usually knew the problem just from a description of the symptoms. Unfortunately, I know longer live around that dealership. I will still take my car to a dealership when it is under warrnaty or I am having a difficult time pinpointing the problem. I just listen to their recommendations with a skeptical ear. It seems nowadays I can't take my car into a dealership without the need for "induction service" or "injector service" along with the problem I wanted addressed in the first place. I go in for a warranty action and they find 500 dollars worth of "maintenance" they should do for me.

Today's cars run on interdependent electronics. The signal from one component initiates signals to the others they react and every error is noted. However, sometimes a slightly off signal can initiate errors in the other components. I have seen a slightly bad IACV cause a TPS and an EGR valve error code but none for the IACV. It still comes down to knowing the vehicle, how it's running and to a large degree where are the weak points in the design. That is why websites like these are so useful. By sharing our experiences we get a better understanding of our particular model, which points to the more likely causes of the problems owners face. I also can't stress enough to clean your engine hands on. When you learn where things are while it is working right, it gets a lot easier to spot something loose or broken when it is acting up. But just like the visual inspection seeks to narrow the possibilities, use the boards here to focus on an area, not as a diagnosis for your particular problem.