1996 xj cts harness

[1996XJ]

Hello everyone I have a couple of questions and need some serious help with regards to my coolant temp sensor located in t-stat housing. So I have a check engine light, rough idle, running rich, key trick neted coolant temp sensor or connector. I put in a new temp switch, but my e-fan is not turning on and still running rich. If i disconect the harness fan turns on. I found a diagram online for the plug connector and bought a new plug part 254 for the connector. Now I know the tan-black wire goes to the pcm so could I just trace this to the pcm tap into it and run a wire directly to my cts harness? As for the blk-light blue wire can I ground this out to the block? Or where does that wire go to? Thanks!

[4.3LXJ]

How long since you changed your O2 sensor? I do realize you have CTS problems, but you may have more than one. The OBDII systems use the ECM to turn on the fan through the fan relay. I would change the CTS first and if that doesn't do it check to see if the relay is getting current to switch it. If so, then change the relay.

[1996XJ]

ok, but the fan works when I remove the cts harness. If the relay was bad wouldnt it not turn on at all? o2 might be an issue, but check engine is cts because I have to remove the harness to get the fan to work. It will not turn on without me disconecting the plug so that leads me to believe that the harness is bad. The cts is new. As for the wiring question do you have any idea?

[4.3LXJ]

Disconnecting the CTS is a test to see if the relay and fan will operate. But you still don't know if the relay is getting a signal or working. But from this I suspect replacing the CTS will solve most of the problem since there is no short involved

[1996XJ]

but that's the problem the cts is new and the issue is still there. So I think the only other thing is the harness. So thats why I want to know if I can wire a cable from the pcm harness cable to the cts plug? The issue is I know the tan-black wire goes to the pcm, but I don;t know what to do with the blk-lt blue wire?

[1996XJ]

anyone else? I really need to figure this out...

[msmoorenburg]

I would check the harness from the plug to the ecu. I would imagine you will find some harness damage where it's been rubbing on a head bolt.