P1698 on my 2001 xj should I replace the TCM

Hello forum I have a code of p1698 and I checked all connections, fine and now should I replace the TCM.::helpme:

More than likely it's a corroded connector or damaged wire. It's pretty rare to have a bad TCM, and that usually manifests as a shifting issue that's not resolved by the usual fixes (tps, failing solenoid, etc).

Is it still shifting okay? The TCM connects to it's own sensors and really doesn't need to talk to the engine computer, aside from reporting error codes.

Start with the free and easy stuff: Visual inspection for melted/chafed damaged wires, inspection for wire plug damage, corrosion, and bent or pushed back wire plug pins. Test the Throttle Position Sensor (TPS) The TCM does use data from the PCM and TPS.



P1698 JEEP PCM Fault No CCD Message From TCM

Possible causes:

• Low battery voltage
• Transmission Control Module harness is open circuit or short circuit
• Transmission Control Module wire circuit poor electrical connection
• Faulty Transmission Control Module (TCM)
• Faulty Powertrain Control Module (PCM)

In a blatant attempt to hijack and bump this (somewhat recent) thread with my own similar, if not identical problem, and just need a lil advice on how to proceed..

99 XJ AW4, P1698 -- I've essentially already pinpointed my issue and it's on the pinout connector to the TCM, specifically the 24, 25, 26 wires (ground, 12v constant, 12v switched, respectively) are fried from a recent boost/jump using a shop unit set to the wrong setting (broken dial :doh. Everything was peachy before that. Now it starts, runs, everything mostly normal except its stuck in the OD gear (in drive, reverse and neutral work) - which points to the TCM and the aforementioned affected wiring..

At any rate, having checked basically everything else (cursory look at relevant fuses [both in the PDC and passenger kick panel], checked grounds and cnxns, unplugged TCM and performed/passed 'manual' mode test, speedo works, gauges good, alternator pushes 14v) without avail, I took a closer look at the TCM plug and yep sure enough those three wires look pretty crusty... granted I haven't put a multimeter to them yet but sometimes a guy gets a hunch, ya know? I've got photos, but am unsure of how to attach them.. if it works, they're at the bottom.

To get to the point, I'm wondering if anyone has any wisdom on how to fix/replace/clean just those three pins if possible for starters, or where to find a whole new plug (I'm in Alaska and junkyards are few and far between and the weather ain't exactly tropical this time of year) and if it would even be possible to realistically splice one in - it's a tricky spot to work in under the dash.

Also wondering, per forum consensus, whether I'll be doing any significant damage by driving it with the TCM unplugged and operate in 'manual' until I can get her proper again. Like I mentioned, everything was gravy before my dumbass tried jumping it on the wrong setting, and as far as I can tell my only issue is the code

I guess that's really the long and long of it, please excuse me I've been a forum member for a bit but this is my first post - I've combed through other relevant posts and was just hoping for some specific advice regarding this unique problem. If I should start a new thread for myself, I'd be happy to do so. Thanks in advance, and thanks for solving all my past issues and problems without knowing it haha!! :cheers:

https://photos.app.goo.gl/aVbaZ8ZUyeTtnw7M6
https://photos.app.goo.gl/CCo2N7PrcsUn8Ec29

In a blatant attempt to hijack and bump this (somewhat recent) thread with my own similar, if not identical problem, and just need a lil advice on how to proceed..

99 XJ AW4, P1698 -- I've essentially already pinpointed my issue and it's on the pinout connector to the TCM, specifically the 24, 25, 26 wires (ground, 12v constant, 12v switched, respectively) are fried from a recent boost/jump using a shop unit set to the wrong setting (broken dial :doh. Everything was peachy before that. Now it starts, runs, everything mostly normal except its stuck in the OD gear (in drive, reverse and neutral work) - which points to the TCM and the aforementioned affected wiring..

At any rate, having checked basically everything else (cursory look at relevant fuses [both in the PDC and passenger kick panel], checked grounds and cnxns, unplugged TCM and performed/passed 'manual' mode test, speedo works, gauges good, alternator pushes 14v) without avail, I took a closer look at the TCM plug and yep sure enough those three wires look pretty crusty... granted I haven't put a multimeter to them yet but sometimes a guy gets a hunch, ya know? I've got photos, but am unsure of how to attach them.. if it works, they're at the bottom.

To get to the point, I'm wondering if anyone has any wisdom on how to fix/replace/clean just those three pins if possible for starters, or where to find a whole new plug (I'm in Alaska and junkyards are few and far between and the weather ain't exactly tropical this time of year) and if it would even be possible to realistically splice one in - it's a tricky spot to work in under the dash.

Also wondering, per forum consensus, whether I'll be doing any significant damage by driving it with the TCM unplugged and operate in 'manual' until I can get her proper again. Like I mentioned, everything was gravy before my dumbass tried jumping it on the wrong setting, and as far as I can tell my only issue is the code

I guess that's really the long and long of it, please excuse me I've been a forum member for a bit but this is my first post - I've combed through other relevant posts and was just hoping for some specific advice regarding this unique problem. If I should start a new thread for myself, I'd be happy to do so. Thanks in advance, and thanks for solving all my past issues and problems without knowing it haha!! :cheers:

https://photos.app.goo.gl/aVbaZ8ZUyeTtnw7M6
https://photos.app.goo.gl/CCo2N7PrcsUn8Ec29

I don't recall how those pins come out, whether you using a pick to press the locking tab down from the front or back. From your picture, it looks like maybe one of the forked tools from https://www.amazon.com/Terminal-Removal-Connector-Household-Extractors/dp/B07V618SJQ/ would work in the backside. If you can get them out, you might be able to clean them up.

For the TCM, Back probe it with the key on and see if you're getting power on the constant power, switch power, and to the #1 solenoid. If you think the TCM it's getting power and not trying to power the #1 solenoid then the TCM is likely fried.

There is no harm manually shifting, just keep in mind it'll run a bit hotter since it won't be locking up the torque converter.

On eBay, includes the connector and a section of the wiring harness.
https://www.ebay.com/itm/185245042776

Yea I guess a guy really should take a multimeter to it to be absolutely sure.. I'll do that and report back.. thanks for the quick response.

Alright well, I backprobed the TCM, got good ground with 12v to constant and switched, and 12v to Solenoid #1, which I tested at the 12 pinout. So does that mean the plug is good and I could have just fried the TCM?

WiscoWanderer said:

Alright well, I backprobed the TCM, got good ground with 12v to constant and switched, and 12v to Solenoid #1, which I tested at the 12 pinout. So does that mean the plug is good and I could have just fried the TCM?

Click to expand...

If it's sending power to the #1 solenoid and not the #2 solenoid, that means the TCU is commanding 1st gear. I wonder if you've got a bad solenoid? You measured it's resistance to ground - should be 11-15 ohms.

https://photos.app.goo.gl/cGDi9FubBipWnT8u8

I got 12v with the switch on from the 26 (12v switched) pinout to all three solenoid pins, 11, 12, 13.
Resistance was 53ish ohms to all three, with the key on, and 12 ohms key off, as measured from 24 (ground) to 11, 12, 13.

WiscoWanderer said:

https://photos.app.goo.gl/cGDi9FubBipWnT8u8

I got 12v with the switch on from the 26 (12v switched) pinout to all three solenoid pins, 11, 12, 13.
Resistance was 53ish ohms to all three, with the key on, and 12 ohms key off, as measured from 24 (ground) to 11, 12, 13.

Click to expand...

Were you measuring the solenoid resistance with the connector disconnected? The 12 ohms with key-off seems good, but the 53-ohms with key-on seems weird and might be skewed if the TCU is still connected. Although I'd still expect them to be different since it should only be trying to power one of them. Is it possible you've fried a ground wire somewhere? Resistance from pin 24 to the battery negative should be very low (key off).

Yea, all the readings were with the TCU plugged in..

lawsoncl said:

Resistance from pin 24 to the battery negative should be very low (key off).

Click to expand...

Battery positive? 24 is ground (which is the same as 12v negative right?); 25 is 12v+ constant, 26 is 12v+ switched, right? I'm far from an electrical engineer and this is by far the most use my multimeter has gotten so I appreciate you bearing with me

WiscoWanderer said:

Yea, all the readings were with the TCU plugged in..



Battery positive? 24 is ground (which is the same as 12v negative right?); 25 is 12v+ constant, 26 is 12v+ switched, right? I'm far from an electrical engineer and this is by far the most use my multimeter has gotten so I appreciate you bearing with me

Click to expand...

Battery negative. You're looking to measure the resistance, to figure out if the ground wire is bad. SHould be very low or the meter saying shorted.

Where do I measure the battery negative from? Straight to the battery with a long lead to the multimeter and pin 24?

https://photos.app.goo.gl/VrMnQumdx7VtXptZ8

Based on what I've read elsewhere, the TCM is grounded through the engine dipstick tube stud, so I'll give that a better inspection... but wouldn't I notice other issues if that ground was compromised?

Yeah back to the battery would be best, or at least to the solid metal body. Never a bad idea to clean up that ground connection at the dipstick. Lots of stuff gets grounded there.

Problem solved - replaced TCM with unit from eBay. Although my plug is questionable, it's functioning and I'd really rather not mess with splicing the harness, especially in that location. Had to clear DTC twice, but yea it seems good. Thanks for all the help!