No bus

[wesley697]

So it started off as my tj would randomly cut power and stumble and then proceed to die some times it would start back up other times I'd have to wait anywhere from 15 min to hours later and it would decide to start back up, I did find a the fuel pump plug slightly lose so I thought but now I wonder if it's the signal wire so I thought that was it checked every other plug I could find but problem Persist so I did check the cel and had what I have done is as follows

Replaced CPS ran better but not fixed same problems persist so I changed the cam position sensor as I was getting a code for intermittent signal loss ckp cmp.
Still same problems persist, then I drove to work about 2 weeks ago it stalled about 10 times on my way home but would fire back up after I'd dump the clutch and bump start after I got it home, I checked codes I had one something about coil C B A primary secondary sercit short or signal loss I can't remember exactly and again ckp cmp intermittent signal loss so,

I started testing wires I came across my signal wire losing it's 5V then complete gone and now it's showing ground on all my signal wires at the pcm plug. Am I supposed to have the plug A or "black plug" plugged in and be back probing or can I have it unplugged and test at the plugs face for my 5V signal wire I have been following this photo I found for pin reference. Now when I connect the scan tool I get linking error along with no bus on my dash.

 

[wesley697]

One other thing I forgot to mention is I have 2 other pcms I had on the shelf I know they won't let the Jeep run but I did swap them in and one does the same thing no bus and no fuel pump no gauges same as the stock one and the other one brings my gauges back and the no bus is gone fuel pump primes and I get spark back but only on 2 plugs I'd assume BC that pcm is for rotor and cap. pic of the 2 pcms that were spares

 

[macleanflood]

It's either a wiring issue, bad sensor issue or PCM.

I'd guess wiring...but I think I'd send my PCM to @Wranglerfix to rule it out as a cause.

-Mac

 

[CharlesHS]

Thoroughly inspect the communication wiring harness from the ECU that runs along the firewall behind the valve cover which is routed around the threaded head stud (right rear corner of head). This harness is known to come in contact with the threaded head stud and rub thru the wiring insulation which causes intermittent shorts to ground.