M925A2 Electrical issue, Circuit breaker/relay issues, Horn/ABS problems

[acolesurf]

Plugged back in the ABS ecu plug, and unplugged the front 3-wire abs unit, and the short at the 15 amp fuse returned. Am I doing this right? I then unplugged the rear abs module too, the short is still there. Is the short in the ABS ECU or downstream somewhere?


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[acolesurf]

This is what I think the problem is, the diode in the ABS ECU, I will take it apart and see.

https://www.steelsoldiers.com/showthread.php?114744-M939-ABS-ECU-failure-point

 

[acolesurf]

How do I open up my PCB box? It seems like the whole thing is welded shut, with only a plug sticking out. Do I have to cut it open with a hacksaw or something? I want to try and see if any of the solenoids are bad. Also, since I fixed the short in the ABS ECU, do you have any ideas on why the horn keeps sounding? It stops when I unplug wire #25, but not when I unplug the wire at the base of the steering column. And it continues to sound even without the 15amp fuse in.

Thanks for the help!!

 

[simp5782]

How do I open up my PCB box? It seems like the whole thing is welded shut, with only a plug sticking out. Do I have to cut it open with a hacksaw or something? I want to try and see if any of the solenoids are bad. Also, since I fixed the short in the ABS ECU, do you have any ideas on why the horn keeps sounding? It stops when I unplug wire #25, but not when I unplug the wire at the base of the steering column. And it continues to sound even without the 15amp fuse in.

Thanks for the help!!

Tap the lip with a screwdriver and hammer. It is a snug fit as it is sealed on to keep moisture out. yet most of them let crap in especially if they sit. Best bet is to drill a hole in the bottom of it so any future moisture can get out.

Could be the bad diode for the horn. I attached some of the p2p program so you can see. The 15amp is the hot wire but pulling the fuse wont cause the horn to drop power. It can cross feed short though is what I meant.

 

[acolesurf]

That's great! I never would have guessed that was a diode. I will unhook it to see if the short goes away. Thanks again for all those pictures, they are great!

Andrew

 

[acolesurf]

I unhooked the diode attached to the horn, and it went back to functioning normally. I must have just blown all the diodes in the truck when the surge occurred. Hopefully everything goes back to normal with the new abs ecu and pcb.


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[acolesurf]

Do you guys know if there are any diodes in the PCB box? Or anywhere else in the truck that I should check out?

Thanks!

 

[simp5782]

Do you guys know if there are any diodes in the PCB box? Or anywhere else in the truck that I should check out?

Thanks!

https://www.steelsoldiers.com/showthread.php?t=113634

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[acolesurf]

Awesome, that's some great info, I didn't see that thread before. I'm definitely going to repair my PCB when I get a chance.

 

[acolesurf]

Thanks so much for all your guys help! I rebuilt the control box I ordered online, And after installing the new delco style alternator, rebuilt PCB box, and new ABS module, the truck runs like a champ! Took it up into the mountains this last weekend and had a blast! Now I just need to rebuild one of the wheel seals so that I can operate the CTIS, and everything should be good! Thanks again everybody!!