ZINGGG

Posting for a friend here

96 Grand Cherokee Laredo, 4.0L, auto

Every year or so, my buddy's PCM in his rig takes a dump, losing all power, everything. He puts in a refurbished one, and it starts to work fine again, but without fail, takes a crap after about a year. He's now on his 4th PCM. Is there an explanation for this happening? Other than the possibility of the PCM being bad from the start?

Bustedback

I would start by checking the charging system and checking for good grounds. Too much voltage can fry the PCM and bad grounds will cause resistance in circuits, resistance causes heat, heat is the enemy to the PCM.

ZINGGG

That's a great place to start, thanks a ton!

CrazyMacaw

X2 what BB said.
There's one ground in particular a lot of people miss and I've seen it cause issues on more than one 4.0L including my own. It's on the right side of the engine on a stud that has a metal wire harness loop in front of it making it nearly invisible. In the pic below I moved things around so the ground ring terminal could be seen better.