Hey, all. I'm sure this has been discussed ad nauseum, but I've exhausted Google looking for a similar issue and have yet to find anything.

Every now and then, my Jeep will die and it is usually caused by the M28 fuse blowing. Usually I can just replace the fuse (I keep a box of fuses in the back) and I'm good to go. But now, it's just popping every fuse I put in there.

Through process of elimination, I've ruled out the PCM and I've isolated it to the C5 TIPM connector. I disconnected it and used a jumper wire to test each pin. Here's where I'm confused.

According to the pinout diagrams I've found online, it's PIN 3. But the diagrams show that that's not connected. I've cut the wire and plugged in the connector, and the fuse doesn't blow. But as soon as I touch the wires together it pops M28.

Instead of pulling out the wiring harness and looking for a damaged wire, I was going to attempt to trace it to its other end and just replace the entire wire. No wire tracers are working though to simplify this.

Has anyone else come across this, or do they have a diagram that shows where PIN 3 on C5 goes? I appreciate anyone's assistance on this. Sorry for the long post.

 

According to my 2008 diagram, (I imagine your 2007 would be the same), M28 leaves the tipm through pin 22 of connector C2, and goes directly to the powertrain control module, pin 11, connector C2.

 

Thanks for the info! I'll check that first thing in the morning, but I read in another thread that M28 goes through C5 and C2. Plus, everything is fine until I connect that one wire.

I put in a fresh fuse and plugged in each connector until it popped and it was C5 every time.

 

I'm having the same issue now on a 2007 JKU, interested to see if you find anything. I'll post my results here also as I track these lines. I disconnected all 4 PCM plugs (assuming this is where the circuit actually goes) and it still pops the M28 as soon as it's installed on mine which makes me think it's a short in between the PCM and fuse (and not the PCM itself). Unless there's something else on this line I guess.. Interested in what you find

 

Found the issue. There was a frayed wire near my OBD port. It was actually the red wire that conne ts to it. Patched it up and the fuse is no longer popping.

 

Found mine too. What a PITA, and frankly should have known better (as always). The aluminum fender liners we installed had a self tap screw as part of the install, the location is directly opposite of main loom. So the tapper went into the loom. Last thing I considered because we've been building this one ground up for months and assumed it had to be somewhere electrical we'd fiddled with more recently. Not bodywork.. sheesh.