At a minimum you’ll need to check the wiring harness. A multimeter would be helpful to test continuity from the PCM to the alternator.

I had P0622 intermittently for a while on my ‘05 LJ. It ended up being that the harness rubbed against the block until the field wire shorted.

 

Thanks, I will check the wire harness.

 

I've attached a photo of what I found.

The harness was rubbing along the back passenger side where the block and head meet. I've since come to believe that the harness needs to rest on the coil rail. If it's between the coil rail and the block, the engine will rub against it as the motor mounts flex.

 

Good find.



Here is what I did to avoid this problem. That harness also has the cam sensor wires (’05-‘06s) which has also caused sensor signal loss in at least one case I know of.

 

Ooohh, that is a good idea. I was thinking last night what I could do to soften the oil dipstick bracket so the wire harness did not rub on such a sharp edge. I will be heading to Home Depot when I leave work to get some Plasti Dip Liquid tape to coat the wiring where the insulation wore through and I will get some rubber hose to put over that dipstick bracket. Great info on this forum!!

 

Thanks for following up. It's good to hear that you found and fixed the issue.

 

Thanks for the great tip! It was quiet for a minute at work today so I did some PM on mine to avoid a potential problem down the road!

 

I was able to get things tidied up this weekend. I did as Rubi 4 My Mrs did and I zip-tied a rubber hose over the oil dipstick support bracket. After inspecting the alternator wire harness good, there was a small area where the insulation had worn through right over the support bracket. I put a couple of coats of liquid tape on the wires to re-insulate the wire. I then put plastic wire loom back over the wiring. Everything is good to go now.