Thank you master tec for your tips and thank you everybody
I change the cranck sensor and that resolved the transmission
Problem my van is working well now

 

Master Tech, do you have a schematic for that harness? i.e. which socket in the TCM connector is the CKP? I'd like to do the conductivity test before popping 199$ plus shipping for a new TCM.

I had the P0725 first, then the CKP died totally (can't remember the code but the van wouldn't start). It was a bugger to get out because the metal around it was so corroded.

Now the van will start and drive in limp mode, with a P725 and P700.

If it is the harness, is the typical fix to just to cut the wire at the CKP and the TCM and solder a new run of wire?

thanks in advance for your help!

dominic

 

Oh, I think I found a diagram that can help:



from http://transtechdiag.com/chrylerdiaginfo.html

That and Mike McLaughlin's comment about pin 6 at the TCM gives me enough information to start debugging.

I'll let you know how I make out :-)

cheers!

 

Found this TCM connector pinout diagram:
http://forums.neons.org/viewtopic.ph...7286&start=206

Good news - I found the crank sensor - I needed to remove the battery and tray to see the connector towards the back of the engine. Then was able to push the connector through the opening into the driver's side wheel well, which made measuring the resistance between the CKP connector and the TCM connector, pin 6, easy .... 0.3 ohms

Bad news - it means it's the 199$ TCM. I'm not looking forward to getting the old TCM out - the long skinny bolts holding it to the carframe are completely rusted.

What's the experience mechanic's solution? Cut the bolts with a hack-saw and find some other way to secure the TCM?

 

YES!! Replaced the TCM and now my van has no MIL and is using all gears!!

Thankfully two of the three bolts came out easily - only snapped the head off of one of them so the TCM is held in by two of the bolts.

 

I know this is an old thread to revive but its a good one, and common problem.

My van recently got the dreaded P0700 annd P0725.

Thanks to Master Techs (and others) posts. I am very close to pin pointing my problem. On my 2003 3.3L it looks to be a problem within inches of the CKP sensor plug. If I wiggle the wires 2-3 inches behind the CKP sensors plug, Both the Limp mode and check engine lite go away for a ride or 2.

 

Well, Now I am up to like Vladhed. I think I need a new TCU. Wiggling the wires was just a fluke.

I found that my TCU case is cracked open at the bottom. Its spewing out powedered aluminum corrosion and road salt collected from this winter. Just looking at it through the front bumper hole and seeing it like this made me consider it to be done.

I hope I dont have any seconday problems to go along with this. This P0700 P0725 has been very hard to diagnose. None of my symptoms make much sense and then poof, trans shifts perfect for a ride or 2. Its in limp mode again now.

Wish me luck. This weekend, I got a heated garage space finally to go and work in. The rebuilt TCU arrived this week. I got it from All Computer Resourses. Looks ok. Its been pre programmed for my Van.

I hope this fixes my problem and I am as happy as you were Vladhed.

 

Ok guys. Vans FIXED. It was a dead dying TCU.

So for future sufferes of P0700 with P0725. I had no CKP Crank Position Sensor symptom problems. Just that the TCU P0725 code for signal problem with crank sensor. My Engine ran fine and my RPM guage/Tachometer worked perfect too.
I got 1x P0725 and 1x P0700 with another P0700 or 2 pending in background on scans.

Help with hardware that holds TCU to van. They are 8mm heads M4 X 60MM long sheet metal screws that go into a rectangle nutzert insert. Not the best. There are total of 3 of everything. Theres 4 holes on the ECU but only 3 are used. Not 4.
I used M6 thread X 60mm. Had 10MM bolt heads on them. I took out the crappy nutzert inserts, usind a step drill, made the holes a bit larger, and tapped them to M6 threads. Put them back and put antisieze on the bolts. Very dirty place to reccorode fast espcially going through all that aluminum on the case.

When removing and installing the TCU. Make sure you have the battery dissconnected. This mean before unplugging and replugging the TCU too.

Heres the biggest help I can pass along to future finders of this fun Caravan fix.

The new TCU, I got my from All Computer resources.com. There seems to be a few out there in Florida with different names but all with the same toll free phone number and address as this place. Only the website address changes. From what I know there is this one Florida place with many names and one more in Texas.
Now, heres the problem. The rebuilder does do the job of fixing the problem but, they dont finish the job 100% properly. You will have to.

These TCU`s are in a terrible location. The motherboards are built in the aluminum case and back filled with dilectric silicone encapsulation gel.

Many Rebuilders dont bother putting back this gel that gets in their way to begin with to do the repair. They leave their work clean and exposed. The covers of the TCU`s are in NO way waterproof at all. If you do no put back this gel, you will have problems. Not if, Its a matter of when.

The rebuilders generally Dont care. They have a lifetime warranty. They have a lifetime supply of parts and just dont care. Its on me and you the end consumer that has to now deal with what happens on the day water shorts out the 200 pin foot of an eprom chip set. Stranded, maybe a tow truck, Who knows. Its hard to know what exacly a drop of water arking 60-200 plus tiny hair like pins will exactly do. It really gets to me that we are the ones stranded because of just not properly finishing the job.

The product to reseal it is not cheap. Its $125 for a small 400ml kit. Thats probablly why these small rebuilders dont do it with new stuff.

The Loctite Product 5625. Part number 1257545 gets you a 400ml kit.

The other fix and this is the one I did was to open up my rebuild unit. (until now I was looking in via the plastic peep hole plug.)
To my amazement, when I opened up my cover, the ripped out ecapsulation gel was stuck to my TCU`s bottom side of the cover. Just not reinstalled to insulate the repaired section of the mother board they had just done.
Manyt of these Encapsulation gels. Are what they call Self healing. They will reattatch itself to itself. The Caravan TCU looks like the Dow Corning self healing stuff. If its clear with a slight brown tint and very sticky. You should be ok. The dark black gel is not self healing and must be patched with new if you find that in your TCU but not likely. Its more common in PCU`s and ECU`s.
I sprayed the open hole in my TCU with Brake parts cleaner. Sprayed the back clean side of my encapsulation gel patch and massaged it in. The brake parts cleaner was on recommendation from a friend at Blue streak that rebuilds ECUs all day long. The fast evaporationg cleaner wont hurt anything. make the hole wet. Put your patch of gel, now as the chemicals evaporate, you get very little air bubbles and almost full contact as, as one evaporates, it draws in the super sticky encapsulation gel.
I would dip my finger in water and massage all the edges until they slowley dissapear and the gel reattatches to itself. If you dont dip your finger in water, the gel sticks too much to skin.

My Buddy at blue streak has seen many ecus fixed like what I mention above. Unsealed work. I understand that small companies have a limited budjet but geez. The stuff can reheal itself in these TCU units. Why not at least do their best to reuse what they allreay got in there for free.

I have personally found this on my own TCU from the place in floriday. I have heard that the one in Texas is the same. But I do not have any personal experience.

If you get a rebuilt TCU unit. Check if the repair has been resealed. If your repair is not resealed like mine was. and If you have no gel, you will have to get the Loctite kit. Sorry.
Or, before you send back your original TCU, Open it up and take its layer of ecnapsulation gel out of it for yoursef. Before taking it out, clean it with water is fine with your fingers. Then cut with a plastic knife and keep it in a clean plastic container until your ready for it.


Ok, other than sticky dilectric encapsulation gel missing issues. The rebuilt TCU works GREAT. Better then what I had in there. Dodge had 3 TCU program varients. The best program is the 3`rd and final program (AE) and thats what all these rebuilders are putting in them. I think it was AA, AB an now AE at the end of the P/N in the TCUs.


Other tips I can give you are to spray the 60pin TCU connector and gasket with a pure clear silicone before dissasembly and after. Helps to release it and helps it to reinstall and seal better. Let all the solvent from the aerosol silicone evaporate before finaly assembly.

Another tip I got from my buddy from Blue Streak. Close the dam FOG Light Hole. The TCU WILL NOT Overheat. But since the Horns are there and the sound has to get out, close the fog light hole with a louvered grill or a screened grill. It will keep rocks and debris from flying in at high speeds that can cut the TCU wiring harness. Plus in major rain, it will help keep the massive amounts of water it engorffs open now, to alot less. Grilled or louvered the horns sounds will still get out and a little breeze is all it needs to dry everything up after puddles from beneath get it wet. I`ll be making my cover tomorrow now that I can drive around for stuff again,... weee.

Sorry for such a long post and babbling on and on.

I wanted to be as overly thorough as I could be to help future sufferers of this problem. There will be more P0725 with P0700 comming considering the ages of these vans and the location of the TCU. It is a magnet for corrosive road salt, water, dirts and sands.

Someone asked: My Van is 2003 3.3l Grand Caravan Sport. From what I know all TCU`s are the same.

 

Dr. Zoom, excellent post with lots of usefull information. Could you add year and drivetrain information to your post?

 

Wow that is quite the post!

I have to admit I just trusted the FL company that sent me the new TCU and didn't give it a second look before installing it.

It's been in the van for almost two years now, including two cold and salty Ontario winters, and it working fine.

Actually I wasn't expecting the van to last this long! It has a persistent P0442 slow EVAP leak code (yes, I changed the gas cap - didn't do anything) and if the rust progresses anymore the doors will fall off. Also the front struts need replacing - probably going to do that next time quick-fit Monroe struts go on sale. The water pump is noisy too - keep expecting that to seize up on me...