M939 SERIES SHUT DOWN PROCEDURES or FRY your ECU!

[Artisan]

So I am digging around the web tonight and I run into the following
and thought I would share it w/ others.

I did a search here and I could not find any info on this, and no one
has ever mentioned it to me. . . ;

Shutdown procedures should be
closely followed on all M939’s
equipped with antilock braking system
(ABS). Otherwise, the electronic control
unit (ECU) may be damaged, faults
created, and the ABS valves will stop
working. Turn the vehicle light switch
off and turn the ignition switch to the
OFF position. Then wait for the engine
to completely stop before turning the
battery switch to the OFF position.

The poop did come from an official publication.

Does anyone have anything to add to this, good bad no yes maybe?

 

[o1951]

Sounds like they are afraid of a voltage spike if the batteries are disconnected while charging system is still in operation (engine running)

 

[o1951]

I am not familiar with M939 5 ton - believe being newer, they have a full air brake system. I think I recall some kind of very dangerous brake lock - up problem and talk in 1990's of possibly retrofitting them with ABS. Some may have been retrofitted. The notice applies only if you have one that was retrofitted with ABS.

 

[commandojeff]

This is common info. You start the truck by turning on the battery switch, then the run switch. Just do it all in reverse. You will mess up the PCB box if you do it wrong.

 

[hndrsonj]

That is a prime example of why the -10 manual for all trucks schould be read before operating.

 

[markmontana]

Important, and has been addressed in previous threads.

Merry Christmas!

 

[jonesal]

Use your search function - this has been discussed in detail, consequences, and possible solutions (mods).

Al Jones