HappyPappy

1990 4.0 Cherokee AW-4.
Did all the checks and replacements of TPS, IAC, did the convertor lock up bypass, and still can't get the tranny to go into "lock-up" mode, without forcing it into lock-up mode.
I've checked the speed sensor, OK, checked all the connections all good. So could it be the TCU bad or maybe it's not getting juice from where ever it's supposed to, could find that circuit. Is there any way to check the TCU , or is there a wiring diagram of it someplace??

MonacaYankee

Did you adjust the TV cable for the transmission? http://www.allpar.com/SUVs/jeep/cher...nsmission.html

cruiser54

That's confusing.

cruiser54

That cable only affects the fluid line pressure in the transmission. Has nothing to do with gear selection or lock-up.

Turbo X_J

Unless you are talking about 1970s GM products then its known as a TV cable, which is an entirely different thing.

89Laredo

My 85 c6 had a kickdown linkage.

Op, how does the trans act? Does it go all the way into 4th and just not lock up or does it stay in 3rd? Does your power/comfort switch light up?

HappyPappy

Adjusted the cable , doesn't due much except makes it shift harder, snappier. It'll shift through all the gears, but the convertor will not lock up unless I use the "lock up bypass switch. The comfort/power switch doesn't do anything other then lite up.

89Laredo

Im thinking you dont have power to the TCU. Check fuse 13 (7.5A) in your box and also the inline fuse on passengers side by the TCU.

HappyPappy

All fuses check OK Seems to me it's not getting power when it's supposed to. It hasn't worked as long as I owned it.

cruiser54

Fuse 13 is the power to the Power/Comfort switch, and just because it's illuminated, doesn't mean it's working. That will not affect torque converter lockup.

The fuse up under the passenger side dash, if it's bad,the trans will start out in 3rd gear.

Just clarifying.

To eliminate the Power/comfort switch and wire it permanently in the Power mode:

Bypassing the Power/Comfort Switch on a Renix Jeep

Remove and unplug the switch. In the harness are 3 wires One has a stripe, one is tan, and the other black. Make a 4" jumper wire with a male spade at each end. Plug one end in the cavity for the tan wire and the other in the cavity for the striped wire and you'll be in permanent Power mode. Stuff the harness back in and reinstall the switch for looks.

If you happen to have a 91 or 92 XJ/MJ and it has the Power/Comfort switch, just jumper the Tan and Blue wires in the harness plug.

NEVER include the black wire when jumpering!!!

89Laredo

I think next thing I would do is check resistance between C14/D7.

Id also check D14 and D16 for 12V with the key on.




Im trying to think of what else would keep it from locking up...



How is your switch wired? Pretty sure mine pulls power from D16 and looks something like this:

HappyPappy

I'll double check all of that today. All the solenoids check out OK when checked at the TCU box.It's got to be something simple, just got to do a lot of poken.

Went back through everything, found diode in backwards at pin 14( can't check ohms if you have a diode inline) have to get before it, but all solenoids check out OK, power from D-16, key on,d-14, C-11, all have power, C-10 only with key on and brake pedal pressed. Have to do a little m more with D-1, can't get anything there, but it is hot at the TPS.

On your diagram, what is above it whereC-8 & C-9 wires go to