I have a 93 Jeep Cherokee. 2W drive, 4.0 liter, 42RE trans. .It does not have a separate trans controller. I believe the trans is controlled from the PCM.Note, the PCM burnt up last August and I replaced it.Everything seemed to run fine.Then I noticed that the RPM was high at highway speeds due to no overdrive. Long story short. I adjusted the shift cable ,pulled down the trans pan, replaced the transducers and the 3/4 accumulator. Did find a broken spring in the accumulator and replaced the whole unit . Also changed the overdrive switch. Still no overdrive. Another note. The message center was not working. Fixed that. Now I get a brake lamp failure message even though the brake and tail lamps work. Also get an occasional coolant temp sensor failure message.This comes and goes. Question, could these two problems also effect my overdrive problem ? I would be grateful to anyone who can help me. This is maddening.

 

Yes it does have a separate trans computer (see pic below), although it's highly unlikely to be your issue. What do you mean by transducers? Solenoids or output speed sensor? Overdrive switch = NSS? If by "overdrive" you mean torque converter lockup versus 4th gear (which is overdrive since it's more than 1:1), then I would start looking at your brake switch and brake light problem since the trans computer will not lockup the torque converter if it thinks you have the brake applied. Also, standard advice is to remove and clean up the ground connections right by the dipstick. A lot of grounds connect there. Inspect the wiring to the coolant sensor right at the connector.

 

Is that photo directly under the glove box ? Thank you for help.

 

If you have the 42RE, then you have a Grand Cherokee (ZJ). Some 93 came with the AW4.

ZJ shifter with the AW4:
P R N od 3 1-2

ZJ shifter with the 42RE:
P R N D 2 1

 

Good point, asking whether it's a ZJ. The 2nd half of 93, the ZJs had a Chrysler trans (and still a separate trans controller).

Yes, the TCM is screwed to the back of the kick panel just below the glove box.

 

OK, I'll check again. But I've had most of the dash panels off and still failed to find the TCM. Are there certain Cherokee models where the TCM is incorporated into the PCM ??