4.7 engine light
 

Try and pull some codes. This is how you do it.
Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock").

If you get "done" then there are no codes.

Yeah, pull codes before throwing parts at it. Shotgun diagnostics is a good way to spend money on unnecessary parts.

To be more specific, "on" is when the warning lights light up, "off" is one click back. The codes will show up in the odometer as "P" codes. At the end of test, it will show "done"

Thanks guys. Where do I cross-reference the code at? Is there a list somewhere?


If it says "Done" and there are no codes where do I go from there?

Most codes are standard for all OBDII systems but some are vehicle specific. Google the codes and see what you come up with or take it to Autozone or some other place and get it scanned. A scanner will be more specific. Actually, if you plan on keeping the jeep for a while, buy a Haynes manual.

"Where do I go from there"?

If it were me. If it is just the CEL. I'd check the air filter or change it, and make sure there are no obstructions/restrictions for air flow in those connections to the air filter.

I'd consider taking it into a mechanic who knows more than I do. Should be easy to find.

I'd just drive it until something else happens. My understanding is the CEL is usually tied to emission controls. I know people who drive around for years with their light on. It doesn't go out and nothing gets worse. That would be annoying to me. But if it really bothered me I'd take it to someone.

To piggyback on ^^^, there are often things that trigger the light that aren't what they say they are (further complicating things). I'll give you a recent example.

On my 2000 WJ, a CEL came on with zero symptoms. I have a great scanner, so I hooked it up and pulled the code. Tool said it was a bad IAC motor (a little doohickey that fits in the palm of your hand and attaches into the side of your throttle body, with a little post that moves in and out of a hole to regulate idle speed).

So, down to the local auto parts store. $70 later, a new IAC motor. Install it, hook it up, clear the codes, clear the memory. The next time I fire it up, five or ten seconds into idling, the light comes back on. "Maybe I got a part that was previously returned", I thought. Back to the auto parts store, swap the part out for a new new one. Back home, install it, hook it up, clear the codes, clear the memory. The next time I fire it up, five or ten seconds into idling, the light comes back on. Call the dealer for advice. Any guesses? "That's a part you always want to buy factory." So over to the dealer I go. $130 later, get home, install the part, clear the codes, clear the memory. Next time I fire it up, five seconds into the idle, the CEL comes back on.

This ate up a lot of time and effort, including when the registration came up (smog check required) and I was unable to proceed with it since a CEL is an automatic fail. Next time I get some money together, I take it to the dealer *shudder* for them to track down the problem. $900 later, they determine there's increased resistance in a part of the wiring harness; they fire it up after that fix, and the light comes back on. A little more diagnostic time later, they determine it's the computer and need to order a new one. (Joyou$$$ne$$$.)

The upside is, now that's all done, and happily, there's no more light on. Moral of the far-too-long story? Even after pulling the codes (which you absolutely, positively SHOULD DO everytime the light comes on), you might end up with something far more complicated than (and sometimes, completely unrelated to) what the codes tell you to fix.

Bon chance!
~CoachJ

My advise? Just get the codes and then we'll help from there.

I have a recurring code in my WJ (P0740) which a scanner says is "torque converter clutch". It could be the solenoid or the clutch itself, but the only difference it makes is about 200 rpm at highway speeds. For 2 years, all I've done is clear the code and drive it. It pops up about every 2 months. It doesn't seem to make any difference in fuel mileage either. Am I worried? No.

I bought a scanner when my wife bought her Dodge Caravan just so I could better service it. It cost me around $100. That was in 97.