M1078A1 Caterpillar pin outs on computer schematic

[Lugnuts]

I really did a search because I had seen where someone had written in about a no start on their engine. I could not find it and I knew at the time I should save it but... So I am asking if I could borrow a cup of schematic for the engine computer so as to check for power and grounds. Please and thank you
I should also ask that if this a common problem maybe someone has an experience or suggestion to throw my way? appreciate it!

 

[GeneralDisorder]

Which engine?

If it's a 3126B, check the jumper harness that the military installed to delete the deprecated EMI filter box near the ECM. The chassis side connectors and the jumper harness itself are prone to water intrusion and anytime I see these I delete them entirely. Cut out the chassis side connectors and splice the wires directly. There's one power and one ground coming in and going out. Don't mix them up or you will damage the ECM. Each of them feeds two pins on the ECM. Two ground pins and two constant 24v battery positive pins.

 

[Lugnuts]

Which engine?

If it's a 3126B, check the jumper harness that the military installed to delete the deprecated EMI filter box near the ECM. The chassis side connectors and the jumper harness itself are prone to water intrusion and anytime I see these I delete them entirely. Cut out the chassis side connectors and splice the wires directly. There's one power and one ground coming in and going out. Don't mix them up or you will damage the ECM. Each of them feeds two pins on the ECM. Two ground pins and two constant 24v battery positive pins.

It is a 3126/ Checked with Caterpillar/ It is not a B/ Thanks for responding/
By the way-would that schematic be the same as a civilian designated 3126?

 

[GeneralDisorder]

It IS a 3126B. That's all the military used in our trucks (besides the 3116 and C7 of course) CAT is often confused with military serial numbers and in any case it doesn't really matter. The chassis side pinout is the same and I believe pretty much the same on the C7 as well.

Since all 3126's use the same computer - civilian or military - they all have the same pinout.

 

[Lugnuts]

It IS a 3126B. That's all the military used in our trucks (besides the 3116 and C7 of course) CAT is often confused with military serial numbers and in any case it doesn't really matter. The chassis side pinout is the same and I believe pretty much the same on the C7 as well.

Since all 3126's use the same computer - civilian or military - they all have the same pinout.

Do you happen to have such the pin out?

 

[GeneralDisorder]

Do you happen to have such the pin out?

It's spread out all over the diagrams. Here's the engine side of the 3126B:



Both connectors (J1 and J2), share the same 70 pin numbering. This is looking at the back of the chassis side - so as if you are staring at the allen bolt that retains the connector to the ECM:



The chassis side wiring is part of the truck schematic. You can find a selection of the A1 through A1R schematics here:

FMTV Schematics A 0 A 1 R : Stewart and Stevenson : Free Download, Borrow, and Streaming : Internet Archive

Family of Medium Tactical Vehicles wiring schematics. A0, A1, A1R WTEC III, A1R Gen IV

archive.org