So my check engine light is on, I took it to a shop and they said it is not giving off any codes any ideas what could cause this?

 

Was the shop capable of reading ALL modules? Anyone should be capable of reading the Powertrain codes, chassis and other modules not-so-much. I'm not sure if the non-P codes light the CEL, though.....

 

I just thought i'd piggy back on this conversation, my engine light is on too, I also had it on the testers and nothing came up, all systems were clear. I have had no other problems just the engine light on, I was able to clear the light each time I tested it, for clarification,( my friends equipment at his shop so I may not be using correct terminology) . Any way as I say we could clear it but each day after it would come back on for no reason. At least not one we could find. So I'd be interested to see what others say...

 

I'm on the same issue. 1997 XJ6L with CEL on and no codes. I've had this issue before but after driving for about 1K miles, it turned off. Since then, I swapped the EGR, Airpump and MAF with my 1996 XJ6 to test everything worked but when put backed in place, the CEL didn't turn off even after a couple thousand miles.

Hoping to get an answer from this thread. Thanks.

 

Hey guys, I think I've finally got a fix for this problem but not really sure what would cause it.

What I did was,
I swapped ECU's between my 97 XJR6 and the 97 XJ6L.
The 97 XJ6L ecu in the XJR6 showed a CEL right away and I was able to view 4 trouble codes. Which were all misfire codes so I just reset all the codes. I had a coil go bad a few weeks ago which is the reason those codes came up but fixed right away and the CEL stayed.
It seems that the codes get stuck in memory and basic ODB II scanners can't see them (I didn't try any advanced dealer scanners)
But anyways, after I reset the CEL for the XJ6L ecu when it was in the XJR6 I put it back into the XJ6L and so far no CEL showing. I've started the car up 3 times and let it idle for about 3 minutes or so and still no light. I still have to test drive the car around to make sure this is a "fix" but so far so good for everything.

Also, with this experience, XJR6 ECU isn't interchangeable with N/A cars. I had a sporadic idle in the XJ6L when installed but the XJ6L ecu in the XJR6, the car seemed to idle fine. I didn't test drive it because I wasn't sure what the effects would be.

Anyways, if you have this problem and another x300 ecu (possibly the same year) this would be a "fix" for it just to get the CEL to go away.