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2002 Chrysler Town and Country. (P0888)

posted Jun 08, 2016 17:19:29 by GerardScarmack
hey Scannerdanner I have a question. when you do the volt test for the relay control sencer (Pin 15) an turn the key you get the right volt reading 11.3 volt turn on. my question is when I do that I get no volt reading down below or up top. (loaded an unloaded). what would be the problem for that? or how could I go about it to fix it? when I get a test ran on it says I need to replace the TCM.https://www.youtube.com/watch?v=EF3Qb2rbAx4
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14 replies
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Tyler said Jun 09, 2016 00:25:35
Hey Gerard!

Just to make sure I'm following you correctly, we're talking about the TCM's power side driver for the transmission control relay, correct? For anyone else following along, here's a link to the point in the ScannerDanner video when he's analyzing the wiring diagram:

https://youtu.be/EF3Qb2rbAx4?t=13m16s

So, you never see power at pin 15 of the TCM, not even momentarily when you turn the key on? That would tend to suggest that there's some kind of issue with the relay driver itself. The flowchart you read may be right on this one :-(

First, I'd suggest verifying powers and grounds at the TCM, making sure that the TCM has everything it needs to work. I'd also suggest carefully checking that relay control circuit for a short to ground, including the relay itself. If that circuit was shorted to ground at any point, then it could have possibly cooked that relay driver.
[Last edited Jun 09, 2016 00:26:33]
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GerardScarmack said Jun 09, 2016 01:45:53
would you happen to have a diagram of this that I could use to go ahead an check the TCM powers an grounds? I know it use to work than sometimes it wouldn't than out of no where it went into a 2ed gear lock out. is there any way that the computer could have lock it out its self because we had it in the garage an they said they couldn't get any readings from the TCM. an said that we would have to get a new TCM.
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Tyler said Jun 09, 2016 03:05:52
would you happen to have a diagram of this that I could use to go ahead an check the TCM powers an grounds?


I found one on the BBB Industries site that'll work. It's tough to send diagrams directly over the forums, but if you follow this link, you'll be able to look up the OE diagram.

I found a main power at pin 56 yellow/red. Also found two main grounds, pin 53 black/yellow, and pin 57 black/light green.

Also found a couple inputs from the FCM (Front Control Module) that are worth checking at the same time. I snapped a pic of the diagram to make it easy:



I'm thinking these are inputs related to ignition switch position, and thus should (hopefully) have some sort of 12V signal on them. I'm not entirely positive what the exact voltage level should be, but I would want to see *some* kind of activity on those wires while cycling through the ignition switch positions.

is there any way that the computer could have lock it out its self because we had it in the garage an they said they couldn't get any readings from the TCM. an said that we would have to get a new TCM.


Wondering if they were referring to a lack of scan tool communication. Just so I'm clear, that means that you can't get codes out of this module, right? But it is going into limp-home mode.
[Last edited Jun 09, 2016 03:06:46]
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GerardScarmack said Jun 09, 2016 19:43:37
yes they was unable to read the TCM. an it is stuck in a limp-home mode (2ed gear). thank you for the information an ill have to try that out thank you so much. ill let you know what I find out.
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GerardScarmack said Jun 09, 2016 20:16:06
both grounds (pin 53 & 57) are getting a good reading (11.36v) battery is at a 11.36v as well. the power (pin 56) is only getting a 3.65v reading.
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Tyler said Jun 09, 2016 23:51:21
Thanks for getting back to us with the results, sir!

both grounds (pin 53 & 57) are getting a good reading (11.36v)


I might be misunderstanding you here, but are you saying your multimeter showed voltage on both of those ground wires with the key on, TCM connector backprobed? That would represent an open ground circuit.

the power (pin 56) is only getting a 3.65v reading.


Whoa, that's not cool! Just to make double sure you're on the right pin, we're talking about pin 56 (yellow/red), with a yellow/violet and black/light green immediately before and after it? If you're confident that your DVOM was giving you a good reading (meter was properly grounded), then I'd say you found the problem.

If you wanted, you could back up your meter reading on that pin by using a test light connected to battery negative, and it should light with the key on.

Pin 56 gets power from fuse 15 (20A) in the Integrated Power Module (same fuse box that you found the TCM relay in). The fuse isn't likely to be blown, but finding 12V on both sides of the fuse would indicate high resistance between the fuse and the TCM.
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GerardScarmack said Jun 10, 2016 02:31:53
yes I triple check to make sure I was on the right pin/color. Yea I seen fuse 15 (20A) on the diagram but I'm unsure what fuse that is in the integrated power module. I ran all the test on the relay. it has power on the bottom left but the top left has no power. that's going back to my very first question that I ask. is there a way that the computer its self shut it down? an I would have to go get them codes erased an put back in? ill have to try it out with my test light.
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Tyler said Jun 11, 2016 16:44:07
I ran all the test on the relay. it has power on the bottom left but the top left has no power.


Right, so there's one constant feed at the relay, which would be from fuse 15. That would suggest that the fuse is good, and that you're looking for a voltage drop on the yellow/red wire between the fuse panel and the TCM.

that's going back to my very first question that I ask. is there a way that the computer its self shut it down? an I would have to go get them codes erased an put back in?


I don't think the TCM is intentionally turning off the relay control, because the TCM isn't alive in the first place (low voltage at the main feed, no scan tool communication). It's my belief that the lack of relay control is a symptom of the problem, not the cause.

I'd suggest rechecking those main TCM grounds with a test light connected to B+. If those check, then you could attempt to supply the TCM with power at pin 56 with a fused jumper wire. Use the lowest rating fuse available. If you now get relay control and communication, then go after the voltage drop on the yellow/red.
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GerardScarmack said Jun 11, 2016 17:56:14
a;; right cool thank you very much. ill have to try that. I know its losing voltage some where cuz something keeps draining the battery.
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Tyler said Jun 11, 2016 19:58:58
a;; right cool thank you very much. ill have to try that. I know its losing voltage some where cuz something keeps draining the battery.


No problem, I'm excited to hear what you find! The deeper we dig into this, the more it seems like the repair shop you went to didn't do enough testing...
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GerardScarmack said Jun 13, 2016 00:46:32
well today I went an got all the stuff to make a fused jumper wire an it WORK!!!!!!!!!
power to the TCM an it shifts an everything is good. thank you very much.

PS: thank you Tyler, and Scannerdanner Crew. for you post on YouTube.
an step by step how to work on things an get them done the right way.
this has save me a lot of money an headache.
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Tyler said Jun 13, 2016 01:32:25
well today I went an got all the stuff to make a fused jumper wire an it WORK!!!!!!!!!
power to the TCM an it shifts an everything is good. thank you very much.


YES! That's awesome, man! I'm very happy to hear that. I think you can take pride in diagnosing this yourself, when most shops would have thrown parts.

PS: thank you Tyler, and Scannerdanner Crew. for you post on YouTube.
an step by step how to work on things an get them done the right way.
this has save me a lot of money an headache.


No problem, sir! I am a bit sorry about where we ended up, 'cause now you get to tear the harness apart looking for a corroded wire :-( You're probably sick of being stuck inside the RF wheel well by now, lol.
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GerardScarmack said Jun 13, 2016 22:29:24
I did not start from down at the TCM. I started from the computer underneath it. an found the break in the line right away it was like 3in down the wire under the computer. an I think that's why it kept losing power was cuz it was sitting on the frame on top of the wheel wall under the computer. I was going to go from the TCM an follow it up but I said nah I was just going to run a new line from the computer down to the TCM an limit it all together with out having to tear it all apart. An I look down the wire a lil to make sure it was the right color an BOOM it was right there all green looking an knew right away that was the bust in the line an that was the right wire. so just had to fix like 5in of the wire and its been ok so far.

thank you again!!
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PaulDanner said Jun 14, 2016 03:24:43
Nice job sticking with it GerardScarmack and thank you Tyler for handling this. You are awesome and I truly appreciate all you do for me here on the forum.
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