M1078 Transmission Wiring Pin Location Map or Knowledge of Pin Locations Allison 3070PT

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Lugnuts

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Gentlemen: I think I really have searched thoroughly for the map for the pin locations on the wiring connections for the transmission on the M1078/ 1997/ Now specifically the one I need is the round quick connect just to the right side rear of the transmission. Allison provides the one for the rectangle one located in the transmission and the GI Tech Manual supplies the one for the TCM and then the one on the front through hull J19 but try if I will I can't seem to locate the one by the transmission. The main reason for this is I have lost signal for the C3 Pressure Switch and I want to diagnose exact location of failure. I know I can use different methods of locating them if I have to but I would like to first turn to y'all to see first if I can get what it is suppose to be by design.
Thank you, Lugnuts
 

Blairg

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California
i can't remember what codes i had but when I got the truck the Tranny didn't work. Got lights on the controller but had a bunch of codes relating to the pressure switches.

It was easiest for me to pull the multi connector off the cab behind the front grill and go through the pins and determine ohm readings of everything in there. I diagnosed we had some bad pressure switches and we took it to my local diesel repair place. He dropped the pan and found a wire had been pinched between the pan and tranny and assumed it was the problem without verifying it. Transmission still didn't work and codes were still being thrown without being able to clear them. Decision was made to pull the pan again and drop the portion that holds all the different sensors and pressure controllers and replace them all. We also went through the internal loom and connectors to verify continuity.

THis time we raised everything back up on a tranny jack and connected all connectors and energized the system to verify that the new parts did the trick without assembling the tranny. Once it verified we put in new transmission oil (got rid of motor oil) and put everything back together.

So far so good,
Blair
 

MrMikey4026

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Location
Eatonville Washington
Gentlemen: I think I really have searched thoroughly for the map for the pin locations on the wiring connections for the transmission on the M1078/ 1997/ Now specifically the one I need is the round quick connect just to the right side rear of the transmission. Allison provides the one for the rectangle one located in the transmission and the GI Tech Manual supplies the one for the TCM and then the one on the front through hull J19 but try if I will I can't seem to locate the one by the transmission. The main reason for this is I have lost signal for the C3 Pressure Switch and I want to diagnose exact location of failure. I know I can use different methods of locating them if I have to but I would like to first turn to y'all to see first if I can get what it is suppose to be by design.
Thank you, Lugnuts
Is this a WTEC 2 transmission? Is the fault C3 solenoid?
 

Lugnuts

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Steel Soldiers Supporter
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Myakka City, FL
Is this a WTEC 2 transmission? Is the fault C3 solenoid?
The code says that the C3 Pressure Switch is open. The main code is 32 and according to the trouble shooting guide any code that begins with 32 goes right to the C3 Pressure Switch. I am going to get back to it and I will finish this thread. So far as Pin Out the pins are h and j and both ends but I have to verify it. That is my next step. Then I plan on taking a pressure test on the C3 port and if I have better than 208 psi the switch should close, if not, bad switch, that is after I verify my wiring.
 

MrMikey4026

Member
85
45
18
Location
Eatonville Washington
The code says that the C3 Pressure Switch is open. The main code is 32 and according to the trouble shooting guide any code that begins with 32 goes right to the C3 Pressure Switch. I am going to get back to it and I will finish this thread. So far as Pin Out the pins are h and j and both ends but I have to verify it. That is my next step. Then I plan on taking a pressure test on the C3 port and if I have better than 208 psi the switch should close, if not, bad switch, that is after I verify my wiring.
Mine had a WTEC3 transmission installed in a WTEC2 truck, I will have to look in my notes to see what the code was.
Is yours an A0 or A1?
You might have Allison check the serial number to confirm you have a transmission that matches your control system.
I will look in my notes tonight. I had to remove the valve body and replace the WTEC3 harness with WTEC2 to fix it.
Has it ever worked since you have owned it?
I went through all my harnesses, to the point of removing them to inspect them, before I found out the wrong transmission had been installed.
Mike
 

coachgeo

Well-known member
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North of Cincy OH
....
I went through all my harnesses, to the point of removing them to inspect them, before I found out the wrong transmission had been installed.
Mike
since it in all reality was not wrong "transmission" may be better said. "....before I found out wire harness was wrong one..."


in another thread would LOVE to know about process to switch harness. I have a Wtech III harness-ed transmission I need to swap to II. Am sure others have or will at some point need same info as well.
 

MrMikey4026

Member
85
45
18
Location
Eatonville Washington
since it in all reality was not wrong "transmission" may be better said. "....before I found out wire harness was wrong one..."


in another thread would LOVE to know about process to switch harness. I have a Wtech III harness-ed transmission I need to swap to II. Am sure others have or will at some point need same info as well.
I think I already have.
I will have to look?
I searched, did not find a post, I will have to get my part numbers found again and write one.
It's hard work but not terribly complicated.
 
Last edited:

MrMikey4026

Member
85
45
18
Location
Eatonville Washington
The code says that the C3 Pressure Switch is open. The main code is 32 and according to the trouble shooting guide any code that begins with 32 goes right to the C3 Pressure Switch. I am going to get back to it and I will finish this thread. So far as Pin Out the pins are h and j and both ends but I have to verify it. That is my next step. Then I plan on taking a pressure test on the C3 port and if I have better than 208 psi the switch should close, if not, bad switch, that is after I verify my wiring.
I was able to download the entire WTEC2 diagnostic and schematic manual online for free.
I am a little perplexed that you have a square connector at the trans, that was only used prior to 9-94?
 

Lugnuts

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Myakka City, FL
I do have a square connector at the transmission but it is internal in the module at the bottom of the transmission. Up above and to the right of the rear of the transmission is a round plug that is the body builders quick connect for the transmission. That round one is what I needed the pin location for but I have found it or so I think. It seems to be the same at both ends of that harness.
 

Lugnuts

Member
Steel Soldiers Supporter
89
15
8
Location
Myakka City, FL
I was able to download the entire WTEC2 diagnostic and schematic manual online for free.
I am a little perplexed that you have a square connector at the trans, that was only used prior to 9-94?
I do have a square connector at the transmission but it is internal in the module at the bottom of the transmission. Up above and to the right of the rear of the transmission is a round plug that is the body builders quick connect for the transmission. That round one is what I needed the pin location for but I have found it or so I think. It seems to be the same at both ends of that harness.
 

MrMikey4026

Member
85
45
18
Location
Eatonville Washington
I do have a square connector at the transmission but it is internal in the module at the bottom of the transmission. Up above and to the right of the rear of the transmission is a round plug that is the body builders quick connect for the transmission. That round one is what I needed the pin location for but I have found it or so I think. It seems to be the same at both ends of that harness.
I do have a square connector at the transmission but it is internal in the module at the bottom of the transmission. Up above and to the right of the rear of the transmission is a round plug that is the body builders quick connect for the transmission. That round one is what I needed the pin location for but I have found it or so I think. It seems to be the same at both ends of that harness.
Odd? See attached picture.
 

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Lugnuts

Member
Steel Soldiers Supporter
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15
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Location
Myakka City, FL
Odd? See attached picture.
Bottom left of picture is located in transmission/ The round one next to the picture of the TCM is the one that I am speaking of/ There are two/ One is labeled J19 and is located to the left of the radiator in the dog house and the other is located to the right side of the transmission/ thanks for the reply
 
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