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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Just finished putting a brand new crate motor (stock 4.0L) in my jeep. Everything is working correctly except now when I put the transmission in drive it starts and stays in high gear. If I put it into 1-2, or 3rd it will go into that gear. Basically, it's not shifting automatically, only manually. The TCM doesn't seem to be working at all. The trans was working fine before the engine swap. I'm looking for ideas of what to check next or how to do a better diagnosis to narrow down the issue.
Things I've checked:
10A fuse in the PDC is good. All fuses are good.
I've disconnected and cleaned out all connectors with contact cleaner. 7 and 8 pin trans connectors, TPS, Speed sensor (both sides)
All grounds are connected. Specifically the three at the oil dipstick which grounds the TCM and TPS
Checked all wires around the trans and bellhousing. Nothing looks exposed or pinched.
TPS, I swapped in a spare good one I had laying around, but no change
The brake switch seems to be working fine. Brake lights come on, TC locks up and disengages fine. The speed sensor seems to be working too because my speedometer is working normally. The jeep will start in park, but it won't start in neutral or any other position. I'm not sure if that's normal or not because I thought it should start in neutral.
Is the TCM receiving and sending signals? How do I check that?
It should start in park or neutral, so the Neutral Safety Switch would be the first thing to check. Easy enough to remove and clean if you haven't already done so. An important trick is to use the nut to pry it off...
The NSS shouldn't cause a lack of 1st gear in (D) though. Having to manually shift is usually caused by no power to the trans computer or a wiring issue. The trans computer is under the passenger side under the glove box, attached to the back of the kick panel. Check that you have power to it (pins D7 and D16), and that the resistance of the solenoids (C14,C15,C16) is around 11-15 ohms. Back probing in park, you should see power to the #1 solenoid (C16) to command 1st gear. There are two connectors on the firewall for the wiring harness going down to the trans. Make sure they're fully connected and that you didn't pinch the wiring between the bell housing and the engine block.
To check for solenoid resistance, test each of the circled pins for 11-15 Ohms against ground. You'll likely find no reading on Solenoid #1 on ping G. It could be coincidence that it stopped working.
Thank you all so much for the replies. I really appreciate it. I finally got some time to pull off the kick panel and check the TCM. Here are the results.
These were taken by backprobing the TCM with the engine running in park, with the multimeter grounded directly to the negative battery terminal.
D7 (TCM Ground) = 3 ohms / 0.0 Volts
D14 (TCM Power) = 14.2 Volts
D16 (TCM Power) = 14.2 Volts
Next I did what Boxburn said and checked the resistance of the G,F, and E pins on the female side of the connector which goes to the transmission. These were each 16.1 ohms.
Should C16 have voltage when in park? If so, it doesn't. Could that be a problem with the NSS?
Also, the resistance of the solenoids is above 11-15ohms, but 1 or 2 ohms doesn't seem like very much. Could that be the issue?
Yeah, C16 should have voltage in park. That 3-ohms to ground seems high (measure with engine off?), you might want to clean the ground connections at the dipstick. No power to C16/solenoid1 will cause it to start in 4th gear unless you manually put the shifter in (1-2). As rare as TCM failures are, I'm reluctant to say it, but this might be a bad TCM if it has power and isn't trying to power S1.
When you put the engine in, did the tCM ground get put on the block?
Cruiser, do you mean the ground on the dipstick tube stud? Yes, I've got all three separate ring terminals bolted to that stud. Also, the ground strap from the back head bolt to the firewall is connected.
The D7 pin on the TCM connector has a resistance of 3 ohms with the engine on or off. According to the electrical diagram I have, that pin is the ground for the TCM and each of the three solenoids in the transmission. 3 ohms seems ok to me, but I might try cleaning that stud again like Lawson mentioned.
Cruiser, do you mean the ground on the dipstick tube stud? Yes, I've got all three separate ring terminals bolted to that stud. Also, the ground strap from the back head bolt to the firewall is connected.
The D7 pin on the TCM connector has a resistance of 3 ohms with the engine on or off. According to the electrical diagram I have, that pin is the ground for the TCM and each of the three solenoids in the transmission. 3 ohms seems ok to me, but I might try cleaning that stud again like Lawson mentioned.
3-ohms is a lot for resistance to ground. The TCU is probably drawing at least an 1/2-amp through the D7 ground pin so you're dropping a couple of volts (not counting the 1-amp per solenoid since those ground through the body).
1.) I checked the resistance on D7 at the TCM connector again and now I'm getting 0.4 ohms. I'm not sure why I'm getting a different reading from yesterday (3 ohms), but it seems like that ground is good. I checked resistance on the dipstick stud to the battery negative and it's also around 0.4 ohms.
2.) When checking resistance of the solenoids as Boxburn said, I probed the female side of G, F and E against the battery negative post and got 14-16 ohms. But, should I be probing G, F and E against the "B" terminal? B looks like it's supposed to be a ground wire on the transmission, right? If I probe G, F, and E against B then I get OL. B against battery post negative I get OL.
3.) With the key turned to accessory, I get voltage of 7.5 Volts on G,F, and E of the male side of that 7-way connector (with the connector unplugged from the transmission female side). Also, back probing C14, C15, C16 on the TCM connector I get 7.5 Volts (makes sense). However, if I plug the 7-way connector into the female side all the voltage drops to 0.0 Volts.
4.) I followed that 7-way connector bundle of wires down to the transmission where it goes into the driver side right above the shifter linkage. There's a big metal wire clamp there that's bolted to the side of the transmission and the wires are running behind it. I unbolted that wire clamp and turns out just about every single wire there is rubbed bare (see picture attached). Do you think maybe the TCM got shorted out and ruined? I pulled all the wires apart from each other where they weren't touching, still got OL on "B" and still no voltage on C16,15,14 when the 7 way connector is plugged in. If I unplug the 7 way connector I can get 7.5 Volts on pin G,F and E on the male side with the key turned on.
Do ya'll have any more detailed schematics of that 7 way connector? Is the B terminal supposed to be a ground? If so, what does it ground?
What is the voltage supposed to be going to that first solenoid in park?
Ok new update. I went ahead and pulled that whole 7 way connector harness off the jeep. The "B" and "C" wires go to the speed sensor in the side of the transmission. I assume B is the ground for that speed sensor. I didn't realize it before, but I guess the TCM uses that speed sensor to control the transmission and the speed sensor in the transfer case is what the speedometer uses. Two totally different speed sensors.
The three "G, F, and E" wires go through a grommet into the transmission. I assume to the solenoids.
The last two wires "A and H" go to a separate plug that was just zip tied to the side of the speed sensor and wasn't plugged into anything. I'm not sure what this is.
The insulation on every wire is totally rubbed off in that area where it was routed behind the clamp. Maybe they were just grounding out against the side of the transmission. I'm going to repair the harness and see what happens.
Yup, the TCM has it's own output speed sensor. I think voltage on the disconnected solenoid wires might be normal and part of how it detects if the solenoid is open circuit. It is possible that it blew the driver, or it was just seeing the short and shutting it down.
11-23-2021, 06:29 PM
Transmission won't shift when in drive
