Diagnose 2001 Chrysler Voyager Transmission EATX

A TRANSMISSION PROBLEM

2001 Chrysler Voyager

4 speed 3.3L 6cyl

Our van's TCM (Transmission Control Module) shorted out on us so we ended up getting a new one. But we learned what was wrong with it by testing the Speed Control Sensors, Solenoid/Pressure Switch Assembly, and the TCM itself. If you are having problems with your transmission and you are on a mission to try and figure out what your problem(s) might be. I hope that this blog will help you someway or another. In this blog I cover the TCM, Solenoid, & Speed Control Sensors. I do not cover anything on the Transmission range sensor. But I do have the Factory Service Manual for the 2001 Town & Country, Caravan, and Voyager.

While my wife was in labor I drove our new-to-us van right into the ground trying to get to the hospital on time. The hospital was about 40 minutes away and we needed to get there pronto. Fortunately we made it there just in the nick of time! Unfortunately about a week later we started having transmission problems! That's what you get for driving like a crazy speed racer, putting too much torque on the motor and transmission.

We she called me while she was stuck on the side of the road. The vehicle went into what is called "limp mode". Limp mode is a "safety" type feature, basically the computer will not allow your vehicle to shift. The van will only stay in Park, First gear, and Reverse. So we had the vehicle towed home where we can work on it. 

I have had van's in the past that have gone into this limp mode before. One of them was an early 1997 Dodge Caravan. This van manufactured the first part of 1997 apparently had wiring harness problems that kept shorting out the Transmission Speed Sensors (input speed sensor, and output speed sensor) as well as many other problems. I took the 01 voyager to Auto Zone to get my codes read to help me determine what the problem was. There were several Diagnostic Trouble Codes (DTC) showing. It pointed out to several possibilities: 1-Speed Sensors (Input/Output); 2-Transmission Range Sensor; 3- Transmission Solenoid/Pressure Switch Assembly; 4-Transmission Control Module (TCM). So I have it kinda narrowed down at this point, but there are still a lot of possibilities!

First off, I am not a mechanic. I am honestly not even very mechanically inclined. This is just a page of information that may help you. These are steps and things that I did to diagnose and solve my tranny problem. So anything that you do, DO AT YOUR OWN RISK! I am not responsible if you get hurt. I am posting this to hopefully help someone else out there that may have the same problem that I had! WHEN WORKING ON YOUR VEHICLE ALWAYS DISCONNECT YOUR BATTERY AND MAKE SURE IT'S NOT GOING TO ROLL ANYWHERE!!!

SPEED CONTROL SENSORS

I know that the Speed Sensors are not that expensive to purchase so I just went ahead and bought a couple of them just in case that is what the problem was. I think that both of them are like $25 or something like that. I could have tested with an ohm reader the ones that are currently in the van to see if they were any good or not before replacing them. But since our van already had over 100,000 miles I figured that it would not hurt to just change them out. I figured that changing them out now while I am in there (if they are not the problem) will be more of a preventative maintenance thing. I did however test them after they were out. I attached my OHM meter and got some readings: The input sensor read .762 on the original one that came out and the new one that I put in read .756 ohms. I am not sure exactly what the numbers mean, but it does tell me that there is continuity flowing through them. Now the Output Speed Sensor original read .670 and the new one read .718. I know that there is a variance in which they will not work properly, I am just not sure what those numbers are exactly (basically you want them to be in a certain OHM range). BE CAREFUL not to mix up the two different sensors nor put them together. Make sure that you do one at a time and keep them from other magnets because they are magnetic themselves.

 

PLEASE notice the DIFFERENCE in the two sensors!!!

If you do not want to replace the sensors, you might want to just test the continuity of them. Maybe find out what the resistance range of them would be. I do not think that places would want to return these once you install them since they will immediately get dirty. This could very well be the problem that you have. So if they are bad you can replace them and then take if for a test drive. Hopefully the problem in yours is not as bad as our was.  But I replaced mine, reset the codes by disengaging the battery and grounding out the positive for a few minutes, and then took it for a test drive...I still had the same problem. So on to the next step.

The Solenoid and the TCM are rather expensive so I was hoping that they were not the problem at all. I was kinda hoping that it was the range sensor even though it was inside the Tans-Axle. The Range Sensor communicates the shift lever position to the TCM

So I had to somehow figure out how to find out what exactly is wrong with it so I just do not go throwing new parts in that do not need to be replaced. The Solenoid was about $200 and the TCM was about $300 new!

I was able to get some advise from a friend on testing things with an OHM meter. I also went and purchased the actual Service Manual for my van from www.techauthority.com and had them rush it to my house so I can start testing things since we did not really have the money for a mechanic. This manual is AWESOME!!! It tells you everything that you need to know about your vehicle and how to fix it. I am sure that you can probably just find one on EBay cheaper but I was in a hurry and there was not one available at that time. These books are so awesome that I had to buy a set of them for my 99 Jeep Cherokee whenever I ever have a problem in the future with that one.

SOLENOID/PRESSURE SWITCH ASSEMBLY

The problem could be the TCM but I was hoping it was the Solenoid since it was a cheaper part. The Solenoid receives electrical power from the TCM through a single wire, that then operates each solenoid individually by grounding the return wire of the solenoid needed. So i had to find a way to test the Solenoid which i do not want to open cause I could make a mess with the fluid and it is not something that you want to open with could cause you to lose the calibration of the different "switches" located inside. The signal opens or closes the individual switches according the proper gear that it needs.
WHEN WORKING ON YOUR VEHICLE ALWAYS DISCONNECT YOUR BATTERY!!!

According to the book, there are 8 pins located on the solenoid. 

Pin #          Function

  1             2-4 Pressure switch sense

  2             Low/reverse pressure switch sense

  3             Overdrive pressure switch sense

  4             Transmission safety shutdown relay output

  5             Underdrive solenoid control

  6             Overdrive solenoid control

  7             Low/reverse solenoid control    <--This is the switch that stays active to allow you to stay in limp mode

  8             2-4 Solenoid Control

Here is a picture with the harness removed. Remove the harness by removing the center single bolt.

 

Here's the way I hooked up to test each individual control.

I stuck my pins of my Multi-meter (Ohm reader) in the harness end of solenoid to try and determine if I was getting signal from the TCM but was unsuccessful at doing so. But I still had to determine if my solenoid was bad. I actually went to a PULL-A-PART junk yard to pull another one off another van just in case that was the problem.

My friend helped me by telling me to put voltage to each of the different switches (I assumed it was the controls and not the senses), but I would have to ground it out first. So I got some alligator clip wire extensions. I put my black wire to pin #4 and grounded it out to the negative terminal of the battery. Again, I am not a mechanic nor an electrician. I could have been electrocuted but I got lucky. Do at your own risk!  Then I attached my red wire to my positive terminal and individually hit pins 5, 6, 7, & 8. You only get one shot at this (unless you want to drive your van to put it back into limp mode to close the controls again) so listen carefully for the individual clicks. *Another thing that I found helpful was to use a mechanic's stethoscope while doing this.* Each click meant that the switch was functioning (either opening or closing). The only pin that I did not hear a noise was pin 7 since this is the switch that stays open to allow you to drive in Limp Mode. So it made it clear to me that the last thing to test was the TCM! :~(. before I reconnected the harness back to the Solenoid, i put some dielectric grease on both sides so they make good contact and keep moisture from damaging the pins.

I would assume that if you did not hear the clicks that the Solenoid would probably be your problem. But again, this was not the problem that we had with the van. Also, when I talked to the Chrysler Mechanics, they told me that they replace a lot of solenoids. So this could be the problem, especially if you did not hear any clicks. If you think that this may be the problem, a mechanic might be able to test it further for you if you removed it and took it to them...Not sure on that one though, I would prob go to a trans shop.

Now onto the dreaded TCM, which was the problem that I had.

TRANSMISSION CONTROL MODULE (TCM)

The book tells me that the TCM is the "brain" of the transmission. It tells it when to shift by receiving signals from all sorts of things such as the Speed Sensors, the Solenoid, the Range Sensor and so many other things. So that kinda told me that it very well could be the TCM since all my codes showed problems with all those things. The TCM is located behind the left fender and is fastened with three screws in the frame rail forward of the suspension. It has a 60-way connector attached.
WHEN WORKING ON YOUR VEHICLE ALWAYS DISCONNECT YOUR BATTERY!!!

 

The TCM is not that hard to get to. Be sure to have your vehicle in park, engage the parking brake, safely jack up you van on level ground, and place a jack stand under you vehicle to hold it up. Don't forget your wheel chocks. 

Remove your driver side tire/wheel and the front panel.

You will then find your TCM right there your right side. Loosen the TCM wiring harness by loosening the center bolt. You are going to find a series of 60 pins. Even though it looks intimidating, it is easier than it looks

With my OHM meter I put my black wire to my pin #57 which is the ground. Then my red wire I pin I touched pins 19, 20, 59, 60 which are my controls. Read below for the pin number function. All four of these were my Solenoid controls and I got a reading of "OL" on my OHM meter meaning open Line. So that means that there was not a connection being made. It is a lot easier to test the TCM after you pull it off and lay it flat on a table.

So then I knew that I needed for sure the TCM. So I went to www.autocomputerexchange.com after finding them on EBay. The had a rebuilt TCM for $200 so i jumped all over it. They did a great job and the TCM that we got in works great. One great thing is that you get a warranty on your TCM once you return yours to them! Thanks A.C.E.!

TCM Pins
1-  TRS T1 SENSE

3-  TRS T3 SENSE

6-  CRANKSHAFT POSITION SENSOR SIGNAL
7-  SCI TRANSMIT
8-  IGNITION SWITCH OUTPUT (START)
9-  OVERDRIVE PRESSURE SWITCH SENSE
10- TORQUE MANAGEMENT REQUEST SENSE
11- FCM OUTPUT (UNLOCK-RUN-START)
12- THROTTLE POSITION SENSOR SIGNAL
13- SPEED SENSOR GROUND
14- OUTPUT SPEED SENSOR SIGNAL
15- TRANSMISSION SAFETY SHUTDOWN RELAY CONTROL
16- TRANSMISSION SAFETY SHUTDOWN RELAY OUTPUT
17- TRANSMISSION SAFETY SHUTDOWN RELAY OUTPUT

19- 2-4 SOLENOID CONTROL
20- LOW/REVERSE SOLENOID CONTROL

41- TRS T41 SENSE
42- TRS T42 SENSE
43- PCI BUS

46- SCI RECEIVE
47- 2-4 PRESSURE SWITCH SENSE

50- LOW/REVERSE PRESSURE SWITCH SENSE
51- SENSOR GROUND
52- INPUT SPEED SENSOR SIGNAL
53- GROUND
54- TRANSMISSION TEMPERATURE SENSOR SIGNAL
55- AUTOSTICK/OVERDRIVE OFF MUX INPUT
56- FUSED B(+)
57- GROUND
58- VEHICLE SPEED SENSOR
59- UNDERDRIVE SOLENOID CONTROL
60- OVERDRIVE SOLENOID CONTROL

Again, this is not a sure fire method to diagnosing your vehicle's problem, but I just hope that it helps. I have the actual Service Manual for this van and if you have any questions that the book can help with, I'll do what I can to help.