fb97xj1

These transmissions are great...when they work. But they are like a VW. Once they have problems, they just keep coming.


I took a trip to get some tires done for the Mustang and half way there the engine felt like it was losing torque. Not long after the engine rpms would rise and fall out of the blue by 1000rpm or so (wasnt paying much attention with all the traffic), and went on for a good 1/2 mile. Then the CEL came on. First thought was that blasted P0700 from a couple months ago came back. So i drove for another 1/2 mile but it got so bad i pulled over, shut it off, and checked the codes using the key. Sure enough, the P0700 (45) was back, no other codes other than 12 and 55. I had to be somewhere so i restarted and drove on. No problems, and no CEL. After another mile or so it started losing torque again and the rpm would rise and fall, but not as severely, and no CEL. I drove on for another mile or so and it had trouble getting out of 1st, as if it were slipping. The rpm would go up but no shift, atleast not until 3000rpm or so. It would eventually grab 2nd on its own with little effort from me. I had enough of this so i turned around and went home. It seemed to run and shift much better on the way home but there was still some noticeable torque loss and the rpm held fairly steady. But no CEL.


What have i tested this time around? Nothing. I know how, im still too frustrated to be bothered and want to push it off a cliff. On fire. Filled with unicorns and rainbows. I absolutely HATE electronically controlled transmissions.


The last time this happened it shifted somewhat decently but was low on torque which was the worst of it, until the CEL started to show up. I replaced the TPS and IAC with Mopar partly because they were old and didnt trust them. The cap and rotor, plug wires, plugs and coil have all been replaced. Grounds are still clean and tight and free of any oil or dirt. The TCU has been replaced with a used one that had no codes, i replaced and adjusted the NSS so it starts in Park and Neutral and reverse lights work, adjusted the TV cable, checked the fluid which is still red and didnt smell burnt.


Once i settle down i will test the shift solenoids. They as well as the torque convertor are on my list, along with the speed sensor. And recheck the BUS. What a day. The good news is that i got the Mustang running after sitting for 6 months (was like a child being born hearing that first cry). Perhaps the XJ is jealous? I shall name said XJ "Sybil".

fb97xj1

Forgot to add that this happened on the highway between 35 and 50mph and 5-6 miles into the trip. I remember checking the gauges and they were working just fine. Voltage was holding steady at 14 with engine temp a little under 210, as always.

fb97xj1

In an effort to understand how my XJ works, would the brake switch play a part in the issues i am having? I found an old post from 2013 that said the plunger should be fully depressed with your foot off the brake pedal. However, that post was for a Renix but i checked mine for the hell of it and the plunger is depressed 1/8" at most with my foot off the pedal, but has another 1" or so until it bottoms out. I can depress it completely with my finger, without sticking. Should that plunger be fully depressed or do i need not worry about it being a 97? The brake pedal arm doesnt swing back far enough to depress the plunger all the way in anyway.


Found that post here if youre curious.
https://www.cherokeeforum.com/f2/tc-...ng-oem-180450/


Also, i found one of the wires going to my switch has a poor mans splice so it might be a good thing i went poking around under there. Its one of those plastic snap connectors that cut thru the insulation, which i cannot stand. There was another wire in there as well at one time for who knows what but has been cut long ago by the looks of it. It wasnt even taped.

Some Guy

The brake switch doesn't need to be fully depressed. If your brake lights are not on when the pedal is not pressed, it's fine. Mine only presses the button about 1/8".
My 97 p0700 code was remedied by taking apart the NSS and giving it a good cleaning, but you said yours is new. Check the grounds on your engine and chassis.

fb97xj1

The battery and grounds are good.


Battery voltage = 12.25-12.27v
All grounds = 12.25-12.27v


I couldnt get the probes to fit securely in some of the TCM connector cavities so i had trouble getting good readings.


Shift solenoids (TCM disconnected):
pin 11 and 24 = 12.1 ohms
pin 12 and 24 = 12.5 ohms
pin 13 and 24 = 12.1 ohms


TCM disconnected (using the DLC):
pins 3 to 4 = 2.45v
pins 3 to 5 = 2.45v
pins 11 to 4 = 2.43v
pins 11 to 5 = 2.43v


TCM connected (using the DLC):
pins 3 to 4 = 2.45v
pins 3 to 5 = 2.45v
pins 11 to 4 = 2.43v
pins 11 to 5 = 2.43v


TCM resistance (using the DLC):
pins 11 to 3 = 60 ohms


TPS voltage (key ON engine OFF):
pin 17 and 24 = .846v closed and 4.02v wide open


The TPS read way high when closed but i dont know if its the wiring or the TPS itself yet, or a poor connection with my probes. Its a Mopar piece and maybe 2-3 months old. I do have a spare on hand i can try, also Mopar. New. We shall see.


For giggles i also probed pins 23 and 24 for the brake switch, using the TCM connector, but not a single reading made any sense as they were all over the map without touching the pedal and jumped around some with the pedal depressed. Whats the proper testing procedure for the brake switch? I had one hell of a time getting my probes to stay in place for the TPS and brake switch so i cant say if those readings are entirely accurate. i will have to do it again.


Thoughts on what happened yesterday with my XJ? TPS is definitely suspect, but i am not ruling out the brake switch just yet until i can test it properly. And the transmission fluid is in good shape...level, color, etc.

fb97xj1

It drove to work yesterday just fine. The idle remained steady and shifted without issue. On the way home a couple hours later the idle was steady and shifted without issue, and the CEL has not come back...yet. As for the rpms rising and falling on thier own the day before and the transmissions 'slipping' i can only assume that even tho the fluid looks and feels and smells ok it may have lost some of its ability to dissipate heat, causing the solenoids to fail once hot. But thats just a assumption. Engine temps have never gone above 210 since i bought it, but i do drive like Miss Daisy.


That TPS voltage still concerns me tho. For all i know that could be the issue right there. Electronically controlled transmissions are not my gig.

CCKen

Your TPS voltages are within FSM specs.


Idle: greater than .26 volts but less than .95 volts.


WOT: less than 4.49 volts.

fb97xj1

And so it is, thanks. I missed that part of the FSM but see it now, under Fuel System 14-32. Not sure what i was thinking with .846v being off. I swear my mind is going to crap. Dont grow old, it sucks.

Radi

The brake pedal switch can cause the torque converter lockup to act up. That's about a 300 RPM change. I don't think that's your problem.
Dropping out of 4th gear, late shifting out of 1'st and feeling like the engine loses power make me think TPS. If not the sensor itself, the ground or wiring harness.

CCKen

I am old, and it does suck.


LOL

CCKen

Stop Lamp Switch test procedures.


Terminals 1 and 2 are for the TCM.


You'll need to remove the switch to test it so you may as well replace it and get it over with.

fb97xj1

I have not tested the brake switch with a meter yet but i have a new on the way. Figured i will need a new at some point as i plan on keeping this thing for a while. This may be nothing but i noticed the brake pedal had some rearward movement, maybe 1/16" to 1/8". Not much. Even tho the the plunger was still depressed it didnt seem right to me, so i pushed the pedal down and pulled the plunger forward, let the pedal go and it did the rest. There is no more rearward movement in the pedal, unless i pull on it obviously which would put it back the way it was. Whether or not it did anything significant i cant say, but it drives ok and the brake lights work. Or was that extra 1/16"-1/8" of slop supposed to be there? I can always put it back where it was.

fb97xj1

Its doing it again, whatever 'it' is thats doing it. Drove to work and back just fine last night. Went to go to work today and as soon as i started the engine, the CEL came on immediately. I didnt even take it out of Park or even touch the brake pedal. I tried to go to work anyway but didnt get very far. A couple hundred feet down the road it felt as if like it was neutral. It wasnt even out of 2nd yet. Without any help from me it fixed itself and away i went. Then the rpms started to jump around. I didnt bother driving much further to see what it would do next as i turned around, went home and bummed a ride to work.


While i waited for a ride i checked codes using the key. As if i didnt already know, i got a 45 (scanner said P0700, again). So i restared it and left it idle for 5 minutes and checked the fluid, in park and in neutral with the engine running. It read the same either way. It was red, did not smell burnt, looked clean and was between the add line and the first hole above it. Was it hot enough? Dont know but i can only assume the fluid is ok. It had been sitting overnight so it was a cold start, so it cant be an overheating issue. Because the CEL came on as soon as the engine was started i can only assume its a ground issue? I checked grounds the other day and everything was good, clean and tight. All showed battery voltage. The TPS voltages are within spec so i ruled that out. The NSS crossed my mind, but i checked that in all gears with a meter at the harness and everything was in working order. The TCM was replaced with a used one the other month. I posted my latest findings a couple posts up. I can try driving with it unplugged, but at what rpm should i shift? There are lots of hills around here. And must i downshift when slowing down or leave it be until i come to a stop and then downshift? I want to cover as much as possible before taking it to the stealership as i am determined to fix this thing without thier help...if thats possible.

There has been no pattern to any of this which is what frustrates me the most.

CCKen

If you get P0700 immediately when turning the key to RUN/ON, it's an electrical fault, not a mechanical fault.


If you used a scanner to pull up P0700 you should have been able to pull up a P07XX code relating to a transmission DTC. P0700 is a PCM DTC indicating that the PCM has detected that an active transmission DTC is present. The TCM has its own diagnostics program and the specific fault must be acquired from the TCM via the DLC.


Some scanners/code readers can be configured for specific vehicles (manufacturer's codes). If your scanner can't be configured it may not be able to acquire the TCM codes.


If you can, see if you can get a different scanner to check for Jeep transmission DTC's.


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The fluid level on the dipstick will indicate low like you describe (cold level), but should be checked when the fluid is up to operating temp (around 150*F). You need to drive the Jeep for around 15 miles then check it. The fluid level then should be at or near the FULL/MAX line.


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Because the CEL comes on immediately it looks like a hard failure in a component input signal o the TCM or the wiring to the TCM is open or shorting out.


You may want to inspect the connectors by the trans dipstick for any defects, like oil covered, and the wire harness looms that go from the connectors down to the transmission for chafing through the loom in to the wiring.


Don't forget that wiggling wire harnesses to see if it changes anything is one of the factory diagnostics steps.


Here's the connectors. Your connector colors may be different and the '97 won't have an ISS.





~~~~~~~~~~~


Do the tests at the TCM connector as shown below.


Use safety pins to probe the connector pin cavities.


Read the connector pin outs and test procedures carefully before beginning.


Safety Pin probe:


You can buy a variety pack of pins. Pick ones that fit the connector pin cavities snugly.



.
Pinouts and procedures. Note that procedure step 2. 3. says resistance unknown ('97 output speed sensor). It should say OPEN - no resistance.


.

.

.

fb97xj1

Thanks for the chart. I remember seeing it, but failed to try it.

First thing i did was check the battery. I got 12.32v at the battery and all grounds. As for using another scanner to doublecheck the codes, i didnt remember until i disconnected the battery. Too late lol.

Resistance checks (battery disconnected):
CAV 24 to ground: 1.9 to 2.0 (i used a TCM mounting bolt/bracket, the brake pedal assembly where it mounts to the firewall, and then the large bolt at the lower left side of the dash, just above the hood release. That bolt gave me a soild 1.8.)

CAV 7 to 6: 60.2
CAV 11 to 24: 12.4
CAV 12 to 24: 12.6
CAV 13 to 24: 12.4


-----------------------

Voltage checks:
Key to LOCK
CAV 25 to 24: 12.15v

Key to RUN
CAV 26 to 24: 12.10v

CAV 18 to 24 (shifter in R): 11.42v
CAV 22 to 24 (shifter in D): 12.30v
CAV 9 to 24 (shifter in 3): 12.30v
CAV 21 to 24 (shifter in 1-2): 12.30v

*Battery voltage still read 12.32v so the 12.30v readings were of little concern. Not sure where to start with the others. Ignition circuit?

TPS:
CAV 17 to 16: .867v at idle and 3.810v WOT

CCD Bus:
CAV 6 to 24: 2.418 to 2.430v
CAV 7 to 24: 2.440 to 2.46v

I blew the IOD fuse in the junction block probing CAV 24 to 25 as the i bumped the probes together, but thankfully the PO left a spare fuse in the fuse panel lid. The terminals were a tad dirty so i cleaned them up with some 400 grit sandpaper. After that i told myself i should probably check the rest of them, so i am currently cleaning them one by one, and they need it by the looks of it. Once thats done i will test everything again.


Edit: Almost forgot, again...

Resistance checks (battery connected): I used the same grounds as i did with the battery disconnected.
CAV 24 to ground:
1.6 (large bolt at the lower left side of the dash, just above the hood release)
1.9 (brake pedal assembly where it mounts to the firewall)
1.9 (TCM mounting bolt/bracket)

Also, while that fuse was blown i noticed that without the hood lamp or interior lights, battery voltage jumped to 12.48v. Seems like a big jump without those tiny lights getting power. Maybe its nothing, but thought id share anyway.