Coyote Posted March 15, 2021 Share Posted March 15, 2021 I've only had my 1988 Comanche Eliminator (4.0 RENIX, AW4, 2 wd) for a couple of months. I've done most of Cruser's tips and it was running great. Recently replaced and adjusted the neutral safety switch, changed all fluids (including trans filter and diff fluid), did the C101 cleaning, added/upgraded battery/block/fuel pump grounds. Also installed a RENIX Engine Monitor, that thing is aweaome. The truck was running like a champ. Took it to the car wash and hosed out the engine bay in prep for fixing old adapter leak. Got the fuel pump relay wet and caused a no start until I could get a new/dry relay. As soon as the relay was replaced it fired right up, drive to the house and the rest of the day was uneventful. The next morning when I hopped in it to go to work it fired right up, but the REM showed ??? for gear (was previously working) and I had to rev it to get it to move, kind of like the transmission was slipping. I drove it less than a block and parked it back in the garage. Since then I've checked the power at the 7.5 amp trans fuse in fuse block, 10 amp fuse going to the TCU (under the passenger knee panel), cleaned and reseated the TCU connection, cleaned/reseated/double checked all engine bay connections, replaced all engine bay relays and added the dash/knee panel ground. My last attempt was replacing the transmission solenoids (all 3). None of that has helped, the REM still shows ??? for gear and the trans still acts like it's slipping. Any suggestions on what might be causing the problem? Terry aka Coyote Link to comment Share on other sites More sharing options...
Minuit Posted March 15, 2021 Share Posted March 15, 2021 You haven't mentioned any change when the shifter is in the "1-2" position. In the absence of electronic control, the AW4 will default to "1-2" being first gear, "3" being third gear, and "D" being overdrive. It almost sounds like your "slipping" is just what happens when you try to start from a stop in fourth gear, and you still have an electronic fault somewhere. If you haven't, give that a shot and see what happens. Have you checked the connector from the neutral safety switch? Link to comment Share on other sites More sharing options...
Coyote Posted March 15, 2021 Author Share Posted March 15, 2021 I only put the shifter in park, netrual, reverse and drive. Haven't tried it in 1-2 or3 yet. I have the oil adapter out right now, but when I get it back in I'll give that a try. I've cleaned, reseated and adjusted the netrual safety switch (replaced within the last month). It appears to be working correctly and passes the function checks. How do you test the electrical connection (like adjusting the TPS)? Do you know how to test the connector that goes to the tranny/solenoids (don't know the name, but it's the gray one in the pic) or the TCU itself? Since it went from working to not working literally overnight I'd assume it was an electrical issue, but I've been wrong before. 😂 Link to comment Share on other sites More sharing options...
cruiser54 Posted March 15, 2021 Share Posted March 15, 2021 CRUISER'S MOSTLY RENIX TIPS TRANSMISSION CONNECTOR REFRESHING OCTOBER 30, 2015 SALAD 19 COMMENTS Over near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itself . These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids. Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in. Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse. Link to comment Share on other sites More sharing options...
Coyote Posted March 15, 2021 Author Share Posted March 15, 2021 Thanks for the tips. I've cleaned and reseated the connectors for the NSS, Trans connector and TCU, but no luck. It just occurred to me that I checked the trans power at the fuse block and inline fuse (under the passenger knee panel), but not at the TCU itself. Do you have a pin out diagram of the TCU, NSS or trans connector so I can check electrical connections? I'm guessing there's a break or short in the wiring somewhere, just trying to track down where it's at. Terry aka Coyote Link to comment Share on other sites More sharing options...
Ωhm Posted March 15, 2021 Share Posted March 15, 2021 3 minutes ago, Coyote said: Do you have a pin out diagram of the TCU, NSS or trans connector so I can check electrical connections? _mj1988electricalmanual_1.pdf Link to comment Share on other sites More sharing options...
Coyote Posted March 15, 2021 Author Share Posted March 15, 2021 That's awesome!!! I'm downloading and saving this forever. Looks like I'll be checking wires for the next week. Lol Link to comment Share on other sites More sharing options...
Ωhm Posted March 15, 2021 Share Posted March 15, 2021 On NIT's website, under TCU Datastream, he show ??? two times. One IDK and the other when Torque Converter_(S3) is FALSE. Could be a good starting point. NickInTime (NIT) Link to comment Share on other sites More sharing options...
omega_rugal Posted March 15, 2021 Share Posted March 15, 2021 you got the engine wet? coe on that´s a beginners mistake Link to comment Share on other sites More sharing options...
Coyote Posted March 15, 2021 Author Share Posted March 15, 2021 Ohm, the wiring diagrams are great. Just got done reading all of it. Under the transmission part is has a note: " For diagnostic procedures refer to MS 1700 and TRANSMISSION MANUAL". Do you happen to have either or those or know where I can get them? Thank you, Terry Link to comment Share on other sites More sharing options...
cruiser54 Posted March 15, 2021 Share Posted March 15, 2021 Is there power at the TCM? How solid is its ground checked with a meter? Link to comment Share on other sites More sharing options...
Ωhm Posted March 15, 2021 Share Posted March 15, 2021 2 hours ago, Coyote said: Do you happen to have either or those or know where I can get them? MS1700 is a tester and the other is a diagnostic manual. Probably Ebay only items. Pin wires for continuity from point to point and do what @cruiser54 saz. Might have something under the DIY section. Link to comment Share on other sites More sharing options...
Coyote Posted March 16, 2021 Author Share Posted March 16, 2021 Pulled the knee panel, disconnected the TCU plug and started checking wires according to the diagram. Every checked good, multiple hots at the plug and good ground. Plugged it back into the TCU and noticed my REM was now displayed 1st gear. I already cleaned and reseated that plug earlier, but I guess it just needed to be done again. Giggled all the connections to make sure there wasn't a short some where. Put everything back together and double checked the REM, everything is still good. 😁 BTW if you pull the 7.5 trans fuse in the fuse block it doesn't seem to do anything, but if you pull the 10 inline trans fuse it kicks it to 2nd locked torque converter. Still haven't put the oil adapter back in so I can't drive it yet, but the REM gear display makes me feel a whole lot better about it. Thank you for all of the help. BTW I attempted to remove the ECU to reseat the plugs. The bottom 2 bolts are easy, but that top one is a bear for sure. That project will have to wait for another day. Lol Terry Link to comment Share on other sites More sharing options...
cruiser54 Posted March 16, 2021 Share Posted March 16, 2021 7.5 trans fuse is for reverse lights, even if equipped with a manual. Also for Power/Comfort switch on the autos. Link to comment Share on other sites More sharing options...
Dzimm Posted March 16, 2021 Share Posted March 16, 2021 So your problem was solved by reseating the plug for the TCU even though you had already reseated it? That's very strange, I've never heard of multiple plug reseats fixing an issue. I wouldn't do anything about it now if everything is working but if you do have issues again check your NSS adjustment. Those NSS are SUPER finiky and are extremely easy to get adjusted just to the edge of where it works but a bump can cause you problems. They also have to be tightened correctly or they will move around when you move the gear selector. Usually it's just the reverse lights working intermittently but I've experienced trans slipping in and out of gear and not shifting because of it being out of adjustment. The NSS tells the TCU what gear it's in as well so if it wasn't on a trace or was getting a signal on two traces it could have caused your REM to display ??? Link to comment Share on other sites More sharing options...
Coyote Posted March 16, 2021 Author Share Posted March 16, 2021 Not sure what's up with the TCU plug. Maybe I didn't get it cleaned or reseated good the first time and the second cleaning/reseating did the trick? At any rate it's working so I'll go with it. Lol The NSS causing issues makes sense to me. I've adjusted/replaced NSSs in Jeeps before, but this one seems to be real touchy. Very little adjustment between starting in park, starting in neutral and reverse lights working. If it wasn't locked down tight I could see it getting bumped out of adjustment while moving the shifter. I'll definitely keep an eye on it and check that first if any more shifting issues come up. BTW it was a cheap ($20) NSS off of Amazon, I have no idea what brand it is. Do you have a preferred brand/more reliable NSS that you like? Just keeping it in mind in case I need to swap it out. Terry Link to comment Share on other sites More sharing options...
Minuit Posted March 16, 2021 Share Posted March 16, 2021 NSS testing diagram in case you need it still: The NSS should have continuity between the pairs of terminals shown above in each shifter position. As for brand, the factory original has never done me wrong. They can be taken apart relatively easily and the terminals cleaned if they get flaky. I disassembled, cleaned, and regreased my NSS in 2013 and it has been flawless since. I don't know if the aftermarket ones are different in construction from the factory, but reconditioning an original and using it instead may be something to consider. I do have a well documented allergy to aftermarket parts, so your mileage may vary. Link to comment Share on other sites More sharing options...
Dzimm Posted March 16, 2021 Share Posted March 16, 2021 That was my next question, I've had many aftermarket ones just not work for me and have heard similar from others. I ended up cleaning up a used Mopar one and it's still working fine today. Most everything I'd recommend the cheapo aftermarket ones but any sensors that measure for the main functions of the drivetrain (NSS, CPS, Cam sensor, ect.) I have had bad luck with aftermarket and would only use a proper Mopar unit. Some people will tell you to use Mopar for all sensors. Link to comment Share on other sites More sharing options...
Coyote Posted March 17, 2021 Author Share Posted March 17, 2021 Success!!! Got the oil adapter put back in and took it for a ride. 1-2 and 3 work as they should. D shifts like it's supposed to and the REM is reading all the gears/locked torque converter. It wasn't the cause of the problem, but the new solenoids make the shifts silky smooth. I even got my best 0-60 time; a blistering fast 8.27 seconds. Lol Thanks for all of the help I really appreciate it and so does the Comanche. Terry Link to comment Share on other sites More sharing options...
Ωhm Posted March 17, 2021 Share Posted March 17, 2021 Link to comment Share on other sites More sharing options...
Minuit Posted March 17, 2021 Share Posted March 17, 2021 8 hours ago, Coyote said: Success!!! Got the oil adapter put back in and took it for a ride. 1-2 and 3 work as they should. D shifts like it's supposed to and the REM is reading all the gears/locked torque converter. It wasn't the cause of the problem, but the new solenoids make the shifts silky smooth. I even got my best 0-60 time; a blistering fast 8.27 seconds. Lol Thanks for all of the help I really appreciate it and so does the Comanche. Terry Hey, 8.27 ain't half bad for a 33 year old, automatic pickup that's shaped like a brick. Faster than a lot of "sports cars" of the day. Of course, that's if the measuring device is trustworthy. Link to comment Share on other sites More sharing options...
Coyote Posted March 21, 2021 Author Share Posted March 21, 2021 Thanks. I'm slow by today's standards, but back in the late '80s these trucks were pretty sporty. They even set a speed record with one. Lol Link to comment Share on other sites More sharing options...
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