IJM

I'm looking for some second opinions on a dealer diagnosis before I dive in on repairs.

I've been having automatic transmission problems recently with my '98 XJ 4.0 where it skips 2nd gear and won't lock up in 4th. I figured it was one of the solenoids going bad, but I didn't have time to deal with it and took it to the local Jeep dealer (yeah, yeah, I know) to chase the problem.

After much diagnosis, they called to tell me it's nothing with the transmission itself or the TCU, and they've identified the problem as some sort of electrical issue with the instrument cluster that's causing a voltage irregularity in the bus and affecting the transmission control.

I called a place that fixes/programs clusters and can have one programmed and at my door for $255 (thanks for the referral from Radi). OK, not bad, as I can swap it out myself easily and not have to pay the crazy dealer prices or screw around at the junk yard.

Before I plunk down the cash on a new cluster, I'd like to get some opinions on the possibilities of some sort of electric issue in the cluster being responsible for the shifting problems. They guy at the cluster shop, who happens to daily an KJ, said he's never heard of this sort of thing, especially since my cluster appears to operate properly. It is possible some sort of loose connection/short in the cluster could be messing up the transmission control like the dealer says?

93gc40

The computerS controls almost every function of the vehicle, motor and transmission and body. A bunch of the inputs/outputs to the computer go through the cluster. SO yes a issue in the cluster can be the cause of many electronic and electrical issues.

CCKen

The only way the IC could be affecting the transmission is if the IC was corrupting the CCD Bus. And if this is the case, there would be other big problems.

Are you having any other problems other than the transmission?

IJM

No, not that I'm aware of. Engine runs like a top. I drove it from DC to Boston and back a couple of months ago, and I use it around town a lot. 4WD works fine as well. Nothing wrong with the other electronics that I can tell. Cluster appears to work fine. Hell, even the A/C works. I did pull the cluster back in April to fix the lose connectors that are a common problem. It's been fine since then.

FWIW, it's throwing two codes: P0700 and P0753.

CCKen

P0753 is the 3-4 shift solenoid circuits.

You can check the resistance of the solenoids/circuits from the TCM connector to see if the is a solenoid problem.

I will give you a link to a thread that shows what to do.

Edit: Read through this thread then do the solenoids resistance checks in post #13.

https://www.cherokeeforum.com/f2/tra...-shift-195148/

CCKen

Here's a pic of your transmission solenoids. Solenoid A is the one in question but there may be another bad one (not 11-15 Ohms).

IJM

The solenoids were exactly my first thought when this started happening a few weeks ago, but the dealership tells me they tested them and they were fine. Now, what they did to test them I can't say.

CCKen

I suggest you do it yourself, following the steps in post #13 in that link.

If you can't do it for some reason, print the page off with the tests and take it to someone with a digital Volt/Ohmmeter so they can do it. You may have to access the TCM and remove the connector for them.

Don't run out and buy an instrument cluster at this point.

IJM

Yeah, I'd agree me retesting them first is the way to go. I do have a good multi-meter, so it should be relatively easy. Hell, the hardest part with these sorts of things is usually getting the damn RTV cleaned off. I appreciate the help.

CCKen

What RTV? There's no RTV on the TCM connector.

If you are referring to testing the solenoids by dropping the trans pan, don't do that. I have a feeling that's what the dealer pukes did. Dropped the pan and read the resistance of the solenoids directly.

You want to read the solenoid circuits, which means the wiring all the way from the TCM to the solenoids. The wiring passes through a connector near the trans dipstick tube and you want to make sure there's no problems with that connector, or in the wiring harness as it goes down to the transmission. Do a visual check on this area for a filthy connector and chafed wires. Make sure the connector is secure.

Here's a pic of the connector I referred to (TCA). Your connector may be Gray.

IJM

Yes, that's what they did and what I was planning to do as well. Your advice makes sense, and it'll also save me having to drop that damn pan in 90 degree weather. Is the TCM up under the dash?

CCKen

Yes, it's under the left dash, to the right of the steering column. See pic.

You'll need to remove the trim panel and knee blocker from around the steering column. Few screws and some snaps.

Always disconnect the battery negative (-) post when doing resistance checks.

CCKen

While you're doing checks at the TCM connector, do the voltage checks of the TPS Input and the Transmission Range Sensor (NSS) checks.

IJM

I picked up the Jeep from the dealership today, but I haven't yet had a chance to check the wiring. I did talk at length with the tech who worked on it. I'm not sure he ever did I resistance check of the solenoid circuits because the first problem he encountered was the transmission not communicating with the bus at all. That problem was supposedly traced back to a faulty open circuit coming from the cluster. He told me he unplugged the cluster from the bus, but when I drove home with it unplugged, the problem came back.

I'm going to try your resistance and voltage tests before I try anything else. I'm still convinced this might simply be a solenoid problem. I'll post with other questions that pop up when I get a chance to mess around with it later this week.

CCKen

Make sure the IC is installed before testing.

I think that tech doesn't know if his **** is drilled or punched.

How could you drive home with the IC unplugged? With the IC removed the CCD Bus is totally dead.