TCU question... Defaults to 4th gear but will shift manually...

I JUST picked UP an 88' with the inline 6 and from my diagnoses it has a bad TCU. A local is parting out a 95 XJ which is also an auto. Are the TCUs swappable?
Thanks

I will make an intro thread as soon as I get the truck halfway decent. Thanks for any help.

Before you go too far, check the inline fuse to the TCU. It's in the wire that goes along the bottom of the dash, in an inline holder. I think from dim past memory that the wire is yellow. This is the symptom of a disconnected/unpowered TCU.

clarify _that wire goes along the inside bottom edge of the dash, behind the knee pad.

Ok my knee pad is already off from the Heater core/blower motor swap i just did... Going to check the fuse now. Hmm where is my flashlight?

Well what do ya know. No fuse! Any idea on size/amp rating? Wonder why PO had it pulled. Maybe the tps or something is messed up and manual shift was the quick fix.

10 amp I think. The 95 TCU won't work in an 88, you'd need one from another Renix Jeep. It'll have a grey connector.

It's possible someone took the fuse out not knowing what it was for. It seems a bit odd that someone would have removed it if it blew, and not tried another. According to a 90 wiring diagram it should be 7.5 amp.

If the TCU is bad, it shouldn't be too hard to find a TCU at a junkyard, because they rarely are needed. If you really cannot find one, PM me. I think somewhere I may still have one from an 89 I took apart. It's been a few years and I can't guarantee I can find it, but I can look, and if I do find it you can have it. My two current XJ's are 5-speeds. But look locally if you can, because I'm not entirely sure about mine.

Well I popped in a 7.5amp fuse because i couldnt find a 10amp lying around. looks like i did ok seeing as thats the recomended one anyway. Bottom line is i put the new fuse in and trans nows shifts perfectly.Yet to find any reason the PO pulled the fuse in the first place... Thanks for the help Guys!