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Interesting - that pinout is not documented in the Dana troubleshooting guide. Looks like as you surmise - pulling the G pin will just re-route the ground for the PCU solenoids to the shield ground - which should be bonded to the CTIS chassis ground internally. In the FMTV harness the PCU 'A'...

Ah I see. You are too light in the back. Makes sense.

Maybe! These things have SUPERB traction due to literally tons of weight on a massive contact patch so it's pretty hard to lock up the tires. Put the tires at 90 psi for the attempt.

If you can get the ABS to activate on anything less than ice or snow my hat's off to you sir.

My guess is someone hooked up incorrectly or applied power to the coms port and blew those resistors. Your DC meter readings on the coms bus is showing the meters averaged interpretation of the 5v square wave. It's not going to be exactly 2.5v because the on and off times are not exactly 50/50...

The resistor spec is something I know from dealing with CANBUS in general - my CAT ECM bench flash cable had to have a termination resistor added..... the 120 Ohm rating is sometimes shown in the schematic and sometimes not but I didn't look at a manual for that information. I'm sure buried in...

I would do an autopsy on the original. Just for giggles. But really a Deutsch DT 3-pin, terminals, wire, and heat shrink is all you need here. No real need to pot it unless you enjoy such exercises. Or you can buy the actual thing if you like: https://www.customconnectorkits.com/dt04-3p-p006/...

You can just use any 1/4 watt 120 Ohm resistor. Jam it into the P250 female terminals and see if she talks. Meg-Ohm readings or even K-Ohm readings are saying bad resistor to me - 11,500 Ohms is nowhere even close to 120 Ohms..... different universe and not going to work. You can switch the...

P250 is supposed to be the harness connector for the R13 termination resistor. Does the matching connector show 120 ohms between C and D? It looked like it would be under the gauge cluster in the TM. But the TM doesn't have the best drawings. But it looks like you found it.

On the diagnostic connector on the truck check the resistance between pins C and D. This should show 120 Ohms - the value of the J1939 bus termination resistor. If it doesn't, pull the dash panel (gauge panel) and find connector P250/J250 and make sure it's securely plugged together. If it is...

Ah - yeah that would do it. I'll have to check but I thought they both lit up on my C7 truck without the laptop connected. :unsure: Different ECM and TCM though.

Do you have access to an oscilloscope? The 3126b CAT computer should be putting out J1939. Check that your diagnostic port has proper power and ground and then look at the scope trace of the data pins. One thing I have found - especially with the 3126b trucks - the data connection is not as...

Yeah not the greatest approach but that is literally what the military would do. Have some grunts clean the wheel speed sensors because in their experience it's the most common issue and often corrects the problem (ABS MIL). So for someone that has no capability to talk to the computer it's at...

The Dearborn Protocol Adapters (3 and 4/4+) are what I use. Yes they connect to the port next to the battery disconnect switch in front of the driver's left knee. That port is a standard heavy duty diagnostic connection used by all medium and heavy duty truck applications. The DPA-3 uses a...

WABCO Toolbox: Used with any laptop and a serial Dearborn DPA-III or a USB DPA-IV, or a NEXiQ adapter, etc. Any RP1210 adapter really.

Easiest thing to do is hookup a laptop with WABCO Toolbox and get the codes - it will also read live wheel speed and it's usually immediately apparent what the issue is...... Without talking to the ABS controller there's really no way to know what it's complaining about. Best you can do is guess...