88 comanchie 4.0 automatic transmission -----HELP PROBLEM

[moconnell]

I have an 88 comanchie, 4.0 with auto trans that does not up shift, i have to do it manually, any idea's someone mentioned it could be the T.P.S. (throttle positioning sensor) never the less i brought it to a transmission shop and the guy there tells me he has worked on it for 2 hours and cannot tell me what is wrong with it, 1st it was the TPS, then he said I have no power going to the tranny, then he tells me it could be the computer or some other type of sensor. Yet now i owe this guy $100.00 diagnosis fee and he can't tell me what the problem is so i am taking it off him today. can any one help or sugest a good tranny shop in the West Roxbury, Mass Area? Please help

Thank You :hijack:

[bbe]

A TCU out of an 87-90 4.0 automatic XJ or MJ will work. 4wd or 2wd makes no difference.

 

I got mine off e-bay for $1.00 plus S&H. Fixed the same issue.

[deziped]

Pull your TCU down to where you can work on it & check the yellow wire going into D 16 on the TCU for power (12 V) with ignition on. If power there check C16 to see if there is any output. Slot D1 should have 5 V coming from TPS. Slot D2 should have a TPS signal. Slot D3 is the TPS ground. Slot D7 is ground for the TCU. Slot C4 is the AW4 diagnostic (Y-T wire) . If there is no power at D16 trace it back to the ECU to verify if any power is coming out of the ECU. If that doesn't help then start swapping with known good used parts. Good luck.

[carnuck]

I found an inline fuse and holder on 2 XJs at the TCU harness, close to the firewall, but not in others.

[ratrapp]

there are 2 tcu fuses for your jeep.the first is in the fuse box and the second is under the passenger side dash in the harness next to the tcu.it's easy to get to and sometimes you may have to replace the inline fuse holder as they corrode and burn sometimes.it these all check out then you may either have a bad tcu or tps.these trannys(aw4)are pretty long lasting and usually don't give much problems if they arent run with oversize tires and have the fluid occasoinally changed.

[cruiser54]

there are 2 tcu fuses for your jeep.the first is in the fuse box and the second is under the passenger side dash in the harness next to the tcu.it's easy to get to and sometimes you may have to replace the inline fuse holder as they corrode and burn sometimes.it these all check out then you may either have a bad tcu or tps.these trannys(aw4)are pretty long lasting and usually don't give much problems if they arent run with oversize tires and have the fluid occasoinally changed.

 

The fuse in the fusebox is for the Power/Comfort switch only. Always a good idea to remove the fuse in the yellow wire to the TCU and clean it and the receptacle.

 

Over near the trans dipstick tube are two connectors, one black and one gray. Unplug them, spray them out with contact cleaner, inspect for bent pins and plug them back in. I have found them to be corroded inside causing intermittent shifting problems.

 

Deziped also gave you some very comprehensive and simple tests that you could do with a $10 voltmeter and would eliminate all the guesswork.