hey, new to forum just a have a question i have an 88 cherokee and the tcu is bad, i found one for sale but its in a 91, will it work in mine? all feedback is appreciated, thanks keith

 

i don't think so. 91 is chrysler and your is renix.

why do you suspect the tcu is bad? how does it shift? what are your symptoms?

 

The following naxja.org post explains why:

1991 aw4 trans question

 

ok thanks, i knew they changed wasnt sure on what year, i just got this cherokee a couple weeks ago and the kid i got it from had it unpluged and said it was bad, so im just takin his word for it, i know its a common problem so i didnt question it, tranny seems to work fine shifting it manually, just has a delay when i put it in reverse when its warmed up, and wont move in reverse when the jeeps cold im sure thats not the tcu

 

nope, it sounds like your throttle positioning sensor on the front of the throttle body.

plug your tcu back in and adjust your TPS. but you may need a new one. you can grab one off a junkyard cherokee of the same year as yours (or any 87-90).
i've been through the same thing. this cured my problem.

 

i tried to ajust the tps with a voltmeter and when i touch the terminals to the wires its showing no voltage at all, is that a bad sensor or an electrical problem, and i didnt know if it wont show voltage if the tcu is unpluged i know there conected?

 

the reverse issue isnt the only problem, he told me it wouldnt shift so thats why its unpluged, and works now manually shifting im gunna plug it in and see what it does

 

fwiw i'd swap out your tps, plug in your tcu and you should good as new.

 

ok, so i put a new tps in and connected the tcu, when i put it in drive it goes in first and wont shift out of it, now i tried to adjust the tps and input its showing between -7.6 to -10.3 while moving the sensor, and the out put is -11.8 to -14.5 while moving it i was questioning the multimeter but when i connect it to the battery its at 12.75v so i think its fine, i was using these directions

THROTTLE POSITION SENSOR (TPS)

1) Turn ignition on. Check throttle position sensor input
voltage. Connect voltmeter negative lead to terminal "B" (M/T), or
terminal "D" (A/T) of sensor connector. Connect voltmeter positive
lead to terminal "A" (M/T and A/T) of sensor connector.

NOTE:

2) Move and close throttle plate completely (M/T and A/T).
Ensure throttle linkage contacts stop. Note voltmeter reading. Input
voltage at terminals "B" and "A" (M/T), or terminals "A" and "D"
(A/T) should be 5 volts.

3) Return throttle plate to closed throttle position (M/T
and A/T). Check sensor output voltage. To do so, disconnect voltmeter
positive lead from terminal "A" and connect it to terminal "C" (M/T),
or terminal "B" (A/T).

4) Maintain throttle plate in closed position (M/T and A/T).
Ensure throttle linkage contacts stop. Note voltmeter reading. Output
voltage should be .8 volt (M/T), or 4.2 volts (A/T).

5) If output voltage is incorrect, loosen bottom sensor
retaining screw and pivot sensor in adjustment slot for a coarse
adjustment. Loosen top sensor retaining screw for fine adjustments.
Tighten screws after adjustment.

 

also the jeep has no speed-o cable in it for some reason will that affect the shifting?

 

if 88 has a speed sensor it could

 

idk if it does

 

renix sensor testing and adjustment valueshttp://www.lunghd.com/Tech_Articles/...iagnostics.htm

 

i checked it that way just now and withthe ground on b and pos on a its got 4.2v and with the pos on d its got 12.9v, thats on the square connector not the flat 3 wire one

 

on here it says the renix era tcu u have grey plug and the obd1 is green, i just pulled my tcu outa the dash and the plug on it is green, im wondering if the kid i got it from put a different tcu in from the wrong year