4wd solenoids don’t receive ground trigger from ecu

W

wigman

New Member
I tested my entire 4wd system-

Actuator works with vacuum actuation
Solenoids click when manually engerized
All the vacuum lines and canister hold vacuum.

As soon as the selector goes into 4wd the lights flash. The solenoids have positive voltage on each terminal no matter what the position of the 4wd selector.

I would assume they are supposed to get a ground signal when the selector is moved but I can’t find any documentation on how the ecu functions

Does anyone have an answer?
 
Generally in this kind of system an ECM provides the grounds to activate the solenoids. This is how electronic fuel injectors work also. Find the ECM and check it for power and grounds per the wiring diagram. If there is a problem at the ECM the system will not ground the solenoids.
 
wigman said:
I tested my entire 4wd system-

Actuator works with vacuum actuation
Solenoids click when manually engerized

As soon as the selector goes into 4wd the lights flash. The solenoids have positive voltage on each terminal no matter what the position of the 4wd selector.

I would assume they are supposed to get a ground signal when the selector is moved but I can’t find any documentation on how the ecu functions

Does anyone have an answer?
Click to expand...
 
I found some Pajero and Montero super select diagrams and figured out the system. The ground is created by the physical switch on the transfercase that gets pushed internally when the selector is moved into 4wd. What I didn't realize is that the ground is completed in 2wd and taken away in 4wd meaning the solenoids are on in 2wd and off in 4wd. So all is good!

I was overthinking that the system was computer controlled like a modern vehicle but really the "ECU" takes in analog signals and uses them to turn the dash lights on/off or flash not to create ground signals for actuation.
 
Thanks for the explanation. I am starting to believe this transfer case is better than its successor. No ECM is appreciated in my book, one less trail failure re drivetrain.
 
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