00 XJ - Check Engine light / No Codes

This is a strange one - I searched and didn't find anything on this. 4.0L engine, not sure on mileage maybe mid 120s? Odometer is off by quite a bit.

In August, the Check Engine light came on. A few months earlier, I had ripped the evap system out by mistake. Had a friend help in hooking it back up. Figured that was what the code was for; maybe one of the lines fell off again.

Grabbed my code scanner and ... no code. Went to a few Advance Auto parts and they couldn't find anything either. Had someone else check it with a big name scanner - still no code.

I cleared the codes (that didn't exist?). Monitors came back up in < 100 miles!

Since I live in the Democratic People's Republic of NY, the vehicle can't pass inspection if there is the Check Engine light on. Inspection is due in September.

Of course, on the way to get it inspected, the light comes on. But with no code.

To my surprise, it *did* pass the inspection with the check engine light on. In a way it makes sense since there were no codes and all the monitors were up and passed.

Cleared it after inspection and it stayed off for a few months. Just came back on with no codes.

Has anyone seen this before? It's quite strange.

You said there were no codes, but were the scan tools able to communicate in general? Could you pull live or any freeze frame data? Could you ping other modules? If not, I would be suspicious that your network (CCD BUS) might be down (although I doubt this would allow the engine to run). If you can communicate with modules but simply find no codes, my next step would be to do the instrument cluster self test (search) to check the functionality of the cluster. Connectivity issues at the cluster can lead to issues and have been heavily documented. Perhaps this will give you a place to start.

I suppose it's possible that it's a manufacturer specific code (DTC). You may try swinging by a Jeep dealership to see if the DRB (Chrysler factory scan tool) can communicate and pull a code. Aftermarket scan tools may be limited and only pull generic DTC's (I know you said you used a more comprehensive unit, but I'm just brainstorming).

The scanner can communicate with the computer. It wouldn't have passed NYS inspection otherwise. I was able to watch as the monitors came online and passed.

Have done IC self test and everything is working there as far as I can tell. My old cluster would drop out and occasionally die - haven't had that happen (yet) with the new cluster.

No Chrysler specific codes - tried the Chrysler scan tool.

Good point on the gauge cluster connection. Just because it isn't dropping gauges before, doesn't mean there is some mis communication. I may yank it out and clean the contacts and see if that can keep it out.