97 XJ data link / shifting issues

• P0135 o2 sensor 1/1
• P1698 No CCD/J1850 message from the tcm

• No CCD bus communication
• No cluster CCD bus message

• will not shift on its own (no 2nd gear, will shift 1st, 3rd, 4th manually with the shifter)
• only gauges that work are volts and temp.

• replaced both battery terminals with good stuff.
• cleaned all grounds in engine bay harness. (3 on distributor side of engine, one on rear of engine, one on each inner fender)
• swapped in a junk yard tcm. Exact same issues.
• measured ccd (data) wire voltage and resistance. Resistance is good always. Voltage is bad unless I unplug tcm. Then it’s good.
• gauges start working when tcm unplugged.
• visual inspection of wiring harness found nothing. I didn’t unloom it, but I was pretty thorough.
• checked all fuses with multi meter. Full volts through all of em.

Skinny said:

It sounds like your main issue is you have a CCD bus problem and everything else is a symptom of that like the trans being in limp mode. It doesn't know how to shift because it has no data.

I would look up the factory troubleshooting and go step by step for a CCD comms failure.

I'm guessing you have a harness issue or one module is shorting out the bus. It sounds like you have done some troubleshooting already but I would suspect any used part.

Click to expand...

Gumbybronco said:

Are you sure the junk yard TCM is good?

Click to expand...

Gumbybronco said:

Have any friends that you could test a TCM on, or barrow their known good TCM.

Click to expand...

Skinny said:

It sounds like your main issue is you have a CCD bus problem and everything else is a symptom of that like the trans being in limp mode. It doesn't know how to shift because it has no data.

Click to expand...

Skinny said:

I would look up the factory troubleshooting and go step by step for a CCD comms failure.

Click to expand...

Skinny said:

I'm guessing you have a harness issue or one module is shorting out the bus. It sounds like you have done some troubleshooting already but I would suspect any used part.

Click to expand...

SLOWPOKE693 said:

This is exactly what it sounds like to me too.

I don't know how that system is set up but I wonder if it has Can high/low in and out pins on the TCM. If so, he can install jumpers from Can high in to Can high out and the same with the Can low side and it should clear everything up but the TCM codes. If it doesn't clear it up he might have a short in the harness somewhere.

Click to expand...

fl0w3n said:

No experience with those codes but the lights bar and pod lights indicate wiring has been messed with, have you traced those to make sure they’re not tied into something dumb?

Click to expand...

Tryloff said:

Light bar is pulled off. Pods are tomorrow’s chore. Head lights are aftermarket too. I will be verifying all the wiring up there and removing all of the goofy lights.

Click to expand...

fl0w3n said:

Did you check power and ground for the TCM?

Click to expand...

Tryloff said:

Yes tcm has ccd at it and is also a terminating resistor. I back probed the connector while it’s plugged in and resistance is good. Voltage drops off with both tcm. Same results no matter which one.

Click to expand...

fl0w3n said:

I'm just interested at this point so I'm trying to see what AI searching can help me do... could be useless, but kinda makes sense to me. Don't shoot the messenger.

There are two separate TCM grounds — a power ground to chassis (BLK/TAN) that carries the solenoid current, and a signal/sensor ground (BLK/LT BLU) shared with the TPS that the data transceiver references.


Voltage is just a reference off ground, so if one of those grounds has a high-resistance connection, current flowing through it develops a voltage drop and the module's local ground floats up ~1.6V. The CCD bus is biased ~2.4V above the module's own ground, so when that ground floats up, the bus lines read ~4V to chassis (2.4 + 1.6) — which is why pins 3 and 11 jumped to 3.99V plugged in. The rest of the bus can't read levels that are shifted up like that, so the bus drops: no cluster, no SRS comms, no auto shift.


The tell that it's a resistive ground and not a clean open: when you unplugged the trans harness the offset shrank from 1.6V to 1.1V. That's load-dependent (V = I×R), so removing current shrinks the drop.


To find it: KOEO, TCM plugged in, meter from each ground pin straight back to the battery negative post (not a nearby chassis bolt) and look for the one reading ~1.6V. That's your bad ground. Then chase it — module pin → splice → body attachment — to see where the drop shows up.


One note on which ground: the load that changed when you unplugged the trans harness is the solenoids, and solenoid current returns through the power ground (BLK/TAN), not the TPS-shared signal ground — so the evidence leans toward the power ground being the resistive one. But load-test both and let the 1.6V call it rather than guessing.

Click to expand...

Mittnz said:

Hey so, I built a tool specifically for this actually, and this is a really cool test case.

ihatethiscar.com — Jeep Cherokee Wiring Diagrams is my XJ site where I've been putting everything. About a third of the way down the page there is a yellow link to an AI diagnostic tool. I know, I know, I'm going to get all kinds of sideways looks and angry responses because mUh ChAtGpT iS aLwAyS wRoNg but, this isn't ChatGPT. This particular AI is armed with all the FSM's I could find, wiring diagrams, and also thousands of old forum posts from Pirate, here, NAXJA, and others.

I went ahead and just copied your first post, and here's what I got back:

Feel free to do the same, and you can go back and forth with it. I didn't load in your more recent posts, just the very first one.
This tool has gotten things right, and has gotten things wrong. But, it should be far more accurate than just "asking AI" because it actually pulls from a knowledge-base of specifically XJ stuff, manuals, and diagrams. Doesn't mean it won't get things wrong, have conflicting information, etc. But, I figure, what do you have to lose? You might get errors related to "API blah blah" if so, just DM me or post here and I'll unlock the tool further. (Every time this tool is used it costs me money from the Anthropic API, it's just pennies, but, up until this point I'm the only person who has really used it, and so I locked it down with a limit so that strangers couldn't find the site and just exploit it or rack up huge bills just to be ****s)

Also, I have all the wiring diagrams on the site too, so if you ever need to look at a quick diagram while you're working on the car, and don't want to go through thousands of pages of PDF manual etc, they are easy to get to. (The site may very well have issues, it's a beta test and just a little pet project I've been working on, really haven't put much time into it lately.)

I'll watch this thread and help if I can, but both of my XJs are pre-OBDII so I'm less of a help on the newer stuff. If you had a Renix XJ, I just went through the exact same thing, and practically rewired the whole car, which is why I built this site in the first place.

Have you ran any new grounds? One thing that helped me was just running "bastard grounds" that way I KNEW that they were good, and not shorting out in the harness somewhere. I'll bet that if you clip off the TCM grounds at the TCM side, and solder on a couple new leads and run them direct to the battery negative, it makes a difference. Start with known good grounds and go from there, or you'll be chasing yourself in circles for weeks.

EDIT: If anyone is interested, here is just part of the information that this Diagnostic tool is armed with:

Click to expand...

Mittnz said:

Well **** now I see that you fixed your issue, haha.
My tool would have been right, so, that's cool.

Click to expand...

wvracer821 said:

i wonder if you can put this in the forum resources somehow.

Click to expand...

wvracer821 said:

i wonder if you can put this in the forum resources somehow.

Click to expand...

How the diagnostic chat works

When you type a question, it goes to an AI assistant (Anthropic's Claude) that reads what you wrote and replies in plain English, like texting a knowledgeable friend. That language ability is the "Artificial Intelligence" part: understanding your question and writing a clear, step-by-step answer.

What is NOT the AI part

Every time you ask something, the assistant is handed a fixed reference document we wrote and fact-checked ourselves: wiring specs, pin numbers, sensor readings, relay tests, and trouble codes pulled from the factory service manuals. That document is not "intelligent." It is a static reference book. The AI's job is to read your question, look to that trusted reference, and explain the relevant part to you.

So think of it as a smart helper who has memorized our verified wiring binder, not a system that invents answers on its own.

Why you can trust it

• Its answers are anchored to that curated, factory-sourced reference rather than random internet information.
• It points you to specific circuit codes (like F22 or K51) that you can look up in our actual wiring diagrams to confirm.
• It is built to ask you for real measurements (voltage, resistance) and to verify power and ground first, the same way a careful technician works.

What to keep in mind

It cannot see or touch your Jeep, so it only knows what you tell it. It is an assistant, not a substitute for a meter and your own judgment. Always confirm critical steps with an actual measurement, and disconnect the battery before unplugging connectors. Like any AI, it can occasionally be wrong, so treat it as a well-informed second opinion.

Click to expand...