Transmission repair in a jeep that caught fire

Hello all,


A while back, I bought a 98 (Mfg Date 12/97) 2wd XJ Classic that had had a fire under the hood. I bought it for cheap as a parts jeep and a learning instrument. The fire melted everything plastic: wires, connectors, vacuum lines, etc. But, the engine ran, even before I did anything to it, so I bought it mostly as a challenge to see if I could ever make it useful again.


Fast forward 6 months, and I’ve kinda been through wiring hell. I gutted the engine and transmission harness, NSS switch, everything that was burned under the hood and replaced it with wiring and vacuum/vent lines from a 98 Sport 2wd in the junkyard (Mfg date 2/98). Somehow, I had more connectors that were different than alike, but I got the jeep back where it was starting normally, reporting codes, even running well. My issues now are all in the transmission.


The fire started from the transmission and burned straight up the firewall, right where the wiring all comes together. I now know that the dipstick tube had been cut off and replaced with hose, and I'm 99% sure that the exhaust got hot and caught that little bit of hose on fire. If thats true, then my AW4 transmission is likely OK. I've just got to make it work, and I've got no real transmission experience.


Here's all the ODB2 codes I'm getting as of now, and some reasons I've compiled. There are several references to the TCM possibly being bad, but I haven't really found a way to test that yet. And yes, there's not any fluid in it right now while I'm repairing the pan/dipstick, but I doubt those are the true source of those codes:

• P1694
  
  • CCD Bus (-) circuit open between Powertrain Control Module (PCM) and Transmission Control Module (TCM)
  • CCD Bus (+) circuit open between PCM and TCM
  • Transmission CCD bus wiring damaged
  • Faulty TCM

• P0700
  
  • Shorted or open circuit within Transmission Control Module (TCM)
  • Faulty Transmission Control Module (TCM)
• P0705
  
  • Faulty Park/Neutral Position Switch
  • Misadjusted Park/Neutral Position Switch
  • Park/Neutral Position Switch harness is open or shorted
  • Park/Neutral Position Switch circuit poor electrical connection
• P0715
  
  • Defective input speed sensor
  • Faulty output speed sensor
  • Damaged, worn, or broken reluctor ring or shaft
  • Bad transmission torque converter
  • Loose, burned, or otherwise damaged wiring and/or connectors
  • PCM failure or programming error
• P0743
  
  • Faulty torque converter clutch solenoid valve
  • Torque converter clutch solenoid valve harness is open or shorted
  • Torque converter clutch solenoid valve circuit poor electrical connection
  • Low transmission fluid level
  • Dirty transmission fluid
• P0753
  
  • Low transmission fluid level
  • Dirty transmission fluid
  • Faulty shift solenoid valve
  • Shift solenoid valve harness or connectors
  • Shift solenoid valve circuit is open or shorted
• P0756
  
  • Insufficient fluid level
  • Dirty or contaminated fluid
  • Dirty or clogged transmission filter
  • Defective transmission valve body
  • Restricted hydraulic passages
  • Transmission has internal failure
  • Faulty shift solenoid
  • Corroded or damaged connector
  • Faulty or damaged wiring
  • Faulty PCM
• P0758
  
  • Low transmission fluid level
  • Dirty transmission fluid
  • Faulty 2-3 Shift Solenoid Valve
  • 2-3 Shift Solenoid Valve harness or connectors
  • P16942-3 Shift Solenoid Valve circuit is open or shorted

While the pan is off, I'm going to be testing/replacing solenoids, but I'm not terribly sure what to do if all those come back as good. I appreciate any help you can offer.

You'll get some of those if the trans computer has no power. The rest look like the result damaged wiring down to the trans. Post back if you the codes come back and we can help sort them out.

98 was a split year on the tranny, later ones had an speed input sensor on the tranny, early ones did not. They are not interchangeable. Sounds like you got one of each.

And I was always told to never run an auto without fluid in it

Unclewolverine said:

98 was a split year on the tranny, later ones had an speed input sensor on the tranny, early ones did not. They are not interchangeable. Sounds like you got one of each.

Click to expand...

Good point that there was a change to the speed sensors in 98. I think the changeover happened between 97 and 98 models, versus mid-year 98. His XJ with a build date of Dec 97 has an input sensor speed error so it's the later version.

If you're still seeing those codes, double check the wire colors and pinout, and that you have all the grounds repaired where they all converge at the dipstick bolt. Do you have a good wiring schematic to work from?

First you guys are awesome!

Second, I think we're onto something...

The wiring harness that I grabbed has a different plug going down to the transmission. I think it's 6 pins versus 8. All of the wires matched in color, but the 2 going to the to the input speed sensor were missing. I read another post on here that seemed to indicate they weren't used, so I just did what I did with all the other harness connectors that didn't match and just T'd off of the original connect with the new one and matched wires. I'm guessing that I've finally found the 1 scenario where that isn't going to work...

I also remember that when I plugged my salvage harness into the tcm, I got the connector to go in, but I had to fitness it a lot. I made sure the male/female plugs matched up and they did, but I had to really fight to get the plug to go in anyway.

Sounds like I have the right transmission and the right tcm but the wrong wiring harness.

FML

What should I do? Do I need to rewire the whole thing again?

SurplusFan98 said:

I also remember that when I plugged my salvage harness into the tcm, I got the connector to go in, but I had to fitness it a lot. I made sure the male/female plugs matched up and they did, but I had to really fight to get the plug to go in anyway.

Sounds like I have the right transmission and the right tcm but the wrong wiring harness.

FML

What should I do? Do I need to rewire the whole thing again?

Click to expand...

Did the color of the harness connector match the color of the socket on the TCM? On the older TCMs, they were color coded and had a small tab or key that normally prevents plugging in the wrong tcm unless you either shave the piece off or force it. Green or grey for example, and red was the color used for the chrysler tranny in the Grands.

It sounds like you might actually have a 97 harness? Or the connector at the TCM isn't actually fully seated.

Start here - https://www.naxja.org/forum/showthread.php?t=1053970 - and figure out what you have, and what you need.

Fill the trans with Dexron-III/Mercon fluid, and then start trouble shooting with the P1694.

Update: It took me about 2 weeks to get another harness, repair a couple of issues with it, and get it in the jeep. Everything snapped together as it should. However, after connecting the battery for a test, i have another issue.


At first I got in and turned the key to on, and nothing happened. I could hear a click when I inserted the key, but not dash light etc. I eventually figured out that I had forgotten to tighten the bolts on the 2 big block connections under the dash, so I did that.


Now when I get in and turn the key to on, everything comes up, dash lights etc. I can get an ODB2 reading and it seems like I'm good to go. But, when I turn the key to engage the starter, I get a big click and everything goes out. I can't even return the key to the on position and get anything after that. When I disconnect/reconnect the battery and repeat this process, its the same thing. Everything comes up and it seems like its going to start, and then ignition clicks and kills it all again. I have repeated this multiple times and its consistent.


Any ideas/pointers?

Clicking and not starting is usually a low voltage issue from:

• dirty, corroded, damaged, or loose battery terminal or wire connections
• internally corroded battery wires
• a short circuit or parasitic drain
• a failing battery
• a failing alternator
• leaving the lights on

Perform routine maintenance of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Battery terminals and battery wire connectors should bright silver, not dull gray/black and corroded. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, wire brush, and clean until shiny the cable/wire ends and whatever they bolt onto.

Jeeps do not tolerate low voltage, bad wire connections, or poor grounds.


Place your DVOM (Digital Volt Ohm Multi-Meter) on the 20 volt scale. First check battery voltage by placing your multi-meter's positive lead on the battery's positive post ( the actual post, not the clamp ) and the negative lead on the negative post. You need a minimum of 12 volts to continue testing. Next, leave your meter connected and take a reading while the engine is cranking. Record this voltage reading. Now connect your positive lead to the battery terminal stud on the starter and the negative lead to the starter housing. Again, crank the engine and record the voltage reading. If the voltage reading at the starter is not within 1 volt of battery voltage then you have excessive voltage drop in the starter circuit.

Typical voltage drop maximums:
• starter circuit (including starter solenoid) = 0.60 volt
• battery post to battery terminal end = zero volts
• battery main cable (measured end to end) 0.20 volt
• starter solenoid = 0.20 volt
• battery negative post to alternator metal frame = 0.20 volt
• negative main cable to engine block = 0.20 volt
• negative battery post to starter metal frame = 0.30
• battery positive post to alternator b+stud = 0.5 volt with maximum charging load applied (all accessories turned on)




Have your helper turn the ignition key to START while you tap gently on the starter with a hammer. If the engine starts, you probably need a new starter.

Test the output at the alternator with your volts/ohms multi-meter. You should be measuring 13.8-14.4 volts. Have the battery, starter, and the alternator Load Tested for proper function in a test machine that applies a simulated work load. Handheld testers are inaccurate and will often pass faulty parts.

Thank you Tim!


I used this and some other sources to fix the issue. I saw that the battery terminal could cause this in several places. Cleaned them up and tested them for voltage drop with a multi meter. That could be a handy thing to add to this guide. Got no drop, and the voltage was good, so I eliminated it and moved on.


I then backed up to the fuse box under the hood. I changed a few things at the same time here and I don't immediately know which was the culprit. I still had the old harness and I knew that in terms of the engine everything had worked before, so I had a good source of fuses and relays. I swapped out the relays for the starter and the ASD. I then noticed, kind of by accident, that in the new fuse box the #9 and #10 fuses were reversed (20 vs 30 amp). I switched those around and gave her a test. Fired right up. I've started it a few times now and re-checked the codes. All thats left is a P0443 (purge valve), which I was half expecting.



Man, this engine/trans combo is just crazy. For anyone reading this in the future, don't be afraid of what others may call a "lost cause" 4.0L jeep. The parts for these are everywhere, and the sources of info are endless. I didn't know an awful lot about cars before I started this. Even if I won't get the money back that I've put into it (and I'm sure I won't), its still the cheapest education I've ever paid for. Patience, used parts, and some basic hand tools will get you 90% of the way there, or better.


Thanks to all who helped!

SurplusFan98 said:

I didn't know an awful lot about cars before I started this. Even if I won't get the money back that I've put into it (and I'm sure I won't), its still the cheapest education I've ever paid for. Patience, used parts, and some basic hand tools will get you 90% of the way there, or better.

Click to expand...

X2. Unless you have zero aptitude an patience and it becomes your worst nightmare. :laugh3:

Reviving this thread for some continued support. I've made progress but I'm stuck again...



Replaced the pan/dipstick/filter/solenoid pack on the old tranny. I filled her up with 3.5q of fluid and ran the truck, clicking through each gear and back to suck up fluid and check for leaks ahead of topping off the fluid. I found one, just not where I was expecting...


There are 2 lines on the AW4 passenger side going to the radiator for cooling. On mine, the front most one is leaking badly at the big hex fitting going into the transmission. I suspect, based on where the fire was, it melted out the little plastic retaining clip inside that fitting and now that cooling line is just kinda loose in there. So question 1 is: to fix, can I just get a replacement plastic clip, pull the whole hex fitting from the yard, or do I need to replace the entire cooling line?


Another thing I'm questioning is the tranny operation itself (I'm not a mechanic, so it may be behaving exactly as it should). I have the drive shaft disconnected from the diff, so the car isn't moving whether the tranny works or not. As I'm cycling through the gears when filling with fluid, the drive shaft never moved in any gear, and I'm getting a P0700 code. The code could indicate low fluid, which is certain (maybe 2 or 3q low for all I know), but idk at what point the drive shaft should be engaged during this process. If its not turning at all, even with low fluid, is that reason to assume that something bigger could be wrong, or am I getting ahead of myself? This thing was always a long shot/learning experience, but I don't want to pour money and time endlessly into a tranny that isn't worth it.



Thanks all!

The cooler line couplers are available at your local part store, go buy new ones. Inspect the lines themselves. I thought my coupler was bad, turned out the line had cracked where the retaining flare was! I don't know at what point the tranny should start turning, but I was also told if you try to put an excessively low fluid tranny into gear, it's a sure fire way to instantly burn it up. But that was many years ago talking about old turbo 350s.

The P0700 code is generic, meaning the TCU isn't happy about something, possibly the NSS if it got damaged. If you're leaking fluid at the fitting, then it's at least pumping fluid. The cooler lines are downstream of everything and return the fluid to the pan, so maybe check they aren't pinched.

I would expect the rear shaft to free wheel in gear though. I doubt you'd burn anything up for low fluid. There's been too many folks posting on here that they fixed their issues by topping off the fluid.


The dorman part number for the connector is 800-714, $12 at NAPA. Be gentle if you try to swap the whole thing instead of just the plastic clip. The aluminum on the trans has been know to break if you cross thread or over tighten it.
https://www.dormanproducts.com/p-28973-800-714.aspx

Dorman lookup for the cooler lines. There are a few threads out the for converting to AN fittings too.
https://www.dormanproducts.com/gsea...Jeep&model=Cherokee&origin=YMM&q=Transmission

I've made some progress on this, but I think the tranny is dead...


I changed the brass fitting. Found a good one at the yard where the lines had already been pulled. Got it and the plastic inserts from Advance, and no more leak. It was a pain to get the old fitting off where the fire had been, but looking at it after I think it was the right thing to do.


I added a TON of trans fluid. It was surprising how empty this thing was. I had to have added close to 7 quarts, and as it sits now its still on the low side of OK. Once I got enough fluid in it and ran through the gears a few times, the drive shaft started spinning and I could feel all the gears shift. My tranny code cleared itself in the computer. I thought I had this thing licked... But...


Really terrible behavior once things started working:

• Park - works as it should but sometimes grinds going in.
• Reverse - works sometimes and not others. When it does work, it can be very reluctantly. I can hear the shift, but sometimes the wheels won't spin without encouragement (revving). Then they seem to pop somewhat violently into place. Also sometimes notice a spinning up and down whine like the gearing is stripped.
• Neutral - works but sometimes the wheels still move slowly forward like it's in 10% drive.
• Drive - works great
• 3rd - Sometimes doesn't work, sometimes works great. Sometimes still hear a whirring noise. Sometimes will spin up, stick, spin up, stick. Kinda random.
• 1/2 - either works fine or doesn't work at all. Kinda like reverse.

Keep in mind that I pulled new-looking solenoids from the yard and tested them. I don't think this is a solenoid or wiring issue. I have no leaks anywhere. I will say that when I pulled the original pan, there was a lot of metal paste inside. Not shavings really, and nothing large, but a lot of magnetic paste.


I've done a little research, and I think my tranny is dead and there's no point in spending any more money on it. I'd love to hear someone defy that point of view though. Its sounds to me like the 1st/reverse planetary gears are basically gone. I wouldn't be surprised. 302k miles and its been in a fire. Pretty sure the people who owned it before were not nice to it either. Just bummed out that I got this far and its not going to be worth it to continue.

Have you actually had it on the ground and tried driving it? Anything I ever had started in the air moved the tires forward in neutral and many of these other issues may resolve after a couple miles of normal use.

Unclewolverine said:

Have you actually had it on the ground and tried driving it? Anything I ever had started in the air moved the tires forward in neutral and many of these other issues may resolve after a couple miles of normal use.

Click to expand...

That's a fair question, and no I haven't. When I got it, this was the partially charred hull of a jeep. Come to think of it, I couldn't even take it off of the trailer when I got it home because it wouldn't roll backwards. I had to disconnect the drive shaft. I can't drive it yet anyway because the track bar isn't on it and I'm not certain the brakes work. I have taken a methodical approach to repairing it. Fixed the wiring first, then worked through the engine codes, then onto the transmission. Thought I'd be able to figure that out before I put it on the road.

I have seen something about a first/reverse brake. What's that?

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You mean a trans brake like a drag car? That's the only one I know of, it is a set up in a power glide that locks it in first and reverse so you can run it up to the converter stall, let go of the button, it drops reverse and you leave the line at 5k, (that's the stall in our camaro.)