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Weird Electrical issue (possible bad PCM)

999 Views 6 Replies 4 Participants Last post by  mukluk
New to the Site.
I just bought a used 06 Wrangler, and it drove great for the first few days, but was having some weird electrical problems. I pulled the battery and had it tested and it was found to be a bad battery (had corrosion and such also). I cleaned the battery ports etc, and it seemed to run fine after that. Then I got a CEL error. I hooked my scanner up to it and read the code and found that it was a gas cap error. Easy enough, right? I cleared the code and then my dash started going nuts (bouncing gauges, no start etc). I pulled the battery and got a new one. I did get power back but now my OBD does not pick up. I have dash lights/radio/headlights/ etc, but I cant crank it. I replaced the ignition switch(thinking that might be the culprit). I even took my battery out of my bigger truck and still had the same issues. Is this an indication of a bad PCM?
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Hey welcome to the forums!

Lets start out with the simple stuff...have you looked at your gas cap, its not rare that the seals on the cap tear and pull a code. I would look at your evap lines and look for possible cracks maybe even have a smoke test done to see if your evap system has a leak. Also sometimes the battery terminals themselves wont seat right or clamp down hard enough on the terminals and cause your electrical system go crazy especially when driving around and you hit a bump.
Checked the cap and tightened it down....Also, I tightened the new terminal post on the new battery and still cant get the thing to start. Gauges dont register, but I do get the brake light and gas light. Thanks for the reply
So far we have these issues:
- Starter will not operate
- Gauges inop when ignition switched on, cluster lamps do work
- OBD port inop/cannot communicate with PCM via scanner
Battery and ignition switch have been replaced.

When you switch the ignition on before taking it to start, can you hear the fuel pump kick on for about two seconds?
Have you checked all your fuses to make sure they are good, no corrosion is present on their terminals, and there is power getting through them?
Does jump starting the Jeep from a running vehicle make any difference?
Try swapping the horn and starter relays to see if the starter will then operate.
If you have aftermarket bolt on battery cable terminal ends, they're garbage. Factory style cables with sealed terminal ends should be used.
Ensure the gang ground point at the right rear side of the engine block and all the cables going to it is thoroughly cleaned and tightened.
I can hear the full pump kick over, and I did check all the fuses. I tested the power with a test light and could see power coming through. I tried jump starting it with another car and still had the same result. When I get home, Ill try the fuse swap. Thanks!
I would check the power cable to the starter.
The loss of the OBD port function and instrument cluster gauges inop but indicator lamps working points toward no power coming from PDC fuse 26. Do your dome lamps and underhood lamp work or are they also inop?

With the ignition turned on, does the HVAC blend door actuator and blower fan work?

Is the Jeep a manual or auto?
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