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Discussion Starter · #1 ·
Hello all, New to the Forum and figured I'd ask around about this new purchase. It's a 2000 Jeep Grand Cherokee Limited 4.7L AWD as the title says I'm having issues with the TCM - Codes p1768 (TCM relay circuitry) p0700 (internal tcm fault) p0132 (o2 shorted)

Lets start with the symptoms -

It runs and drives fine! Sluggish on takeoff because it starts in 3rd gear and stays there but it will cruise all day long with no major issues other than MPG.

occasional (ABNORMAL - not just park on hill and shift into drive type) clunking when put into gear (Drive or reverse)

off and on rough idle 2 minutes or so apart between cycles of good and bad (never seen that before but likely due to p0132)

CEL Obviously..

Here's what I have discovered so far.

Aftermarket audio system from hell.. Sirius radio tuner, 1000 watt amp, Blown subwoofer, Ipod integration device and more. Was about the most complicated system I have ever seen from the era of this thing. The head unit was not working and the amplifier power feed was full of corrosion (That's the reason I'm bring it up.) so I have removed all aftermarket accessories to help eliminate possible problems or interference with the diagnostic process.

First thing in an electrical diag! Check the fuses!!
in the PDC I found 0 volts at TCM fuse on either pole!! Fuse was not blown
Later I test and find 13.37 (voltage of the battery while running at the time)
I run a continuity test from negative terminal of the battery and hear the ominous beep
I run an ohm test at 200 to determine how bad of a fault and discover 186 ohms
I pulled the fuse box and checked for any signs of corrosion or broken wires and found none on either side
I checked the wiring harness running from the fuse box towards the firewall and found no breaks or tampering
I ran a jumper from the positive terminal to the load side of the fuse for the TCM as a test to see if the transmission would resume working after clearing DTCs and it would not. Still have all 3 DTCs even with the wiring bypassed.
I had a transmission shop diagnose my problem and labeled it as an "External electrical problem having nothing to do with the transmission" Clearly I'm not so certain of their diagnosis - I believe I am facing a wiring issue that has blown out my TCM.
Just to note - the transmission will manually shift with the gear selector into 2nd gear but not 1st - It will also shift back into 3rd on its own.

Later I will be disconnecting the o2 sensor that is grounded or shorted and inspecting the wiring to see if that could be a potential problem (Perhaps some sensors run on the same reference feed? No clue, Desperately need a wiring schematic and cannot find one)

I will be updating as I continue to go through this project of mine in case anyone else has similar problems in the future, or has had in the past and can shed some light. Thank you for any help you can offer!

If anyone has any schematics for TCM wiring on the AWD 4.7L I would very much appreciate a share! thanks all!
 

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Discussion Starter · #2 ·
UPDATE
Haven't done too much today with the diag but I did do some tests and disconnected the o2 sensors, Doing this resolved the rough idle (not surprising to me) but did little else. I did find a broken ground on the drivers side coming from the o2 wiring harness underneath the manifold bolted near cylinder 5. Will be making some repairs there and possibly running a new ground from terminal to block because I'm not impressed with the present ground situation. I doubt this will resolve any issues but it will make me feel better Shrugs
 

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Discussion Starter · #3 ·
Well another update... I rolled my 97 cherokee 4 times and am now forced to drive this instead of it being a project. Ordinarily I would be complaining but I'm just glad to be alive as the air bags did not go off and apparently I'm not smart enough to wear a seatbelt or go the posted speed limit. Working on the jeep has been an impossibility as I had a concussion and severe road rash on my head and arm. I'm healing nicely and for the last week I have found a few issues with the 2000 - one being that it accumulated 25 codes, mostly duplicates Pending Confirmed and one actually said Permanent on Mil status.. P1685 is one of the new codes. 2 others that I can't remember the code but know what they are for. ASD relay circuitry and 4c pressure switch circuitry I have tested the ASD and bypassed it temporarily and can say it functions correctly so maybe a hiccup from other issues? The most troubling is the P1685 obviously. That's vehicle immobilizer which I have had the displeasure of trying to reset and being stuck once already. I am still looking for a wiring schematic for a 2000 jeep grand cherokee that includes o2 sensors - Google search is never friendly with that information. Always get the wiring schematics for other vehicles instead of my own
 
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