4wd actuator not actuating

Bummer. Now you did check the one on the Tcase right? Not the one on the front diff?

If so, then yea, your A.D.D. actuator is the next thing you'll want to check. The motor could just be bound up internally, especially if you hadn't been using 4WD often.

 

That was my line of thinking since it did look like some water got in there and I haven’t used 4wd since like February. I have a spare motor actuator assembly I’m going to pick bits off of later and see what makes something happen. While messing with the transfer case yesterday it seems I have spun it into 4wd by hand, which would trigger that position sensor right? Still no light at all though. Had to drive to work this morning with the case in 4hi lol

 

So the position sensor on the tcase just tells the truck once the tcase has engaged 4wd (doesn't do anything for the light), then and only then will the ADD actuator engage and now the truck is actually in 4WD. Thats when the position indicator switch on the front diff can detect that 4WD is active and it signals the 4WD ECU to illuminate the light on the dash

 

Does the position switch on the diff trigger the blinking light? I guess I’ll be checking that later as well. Does it work the same as the tcase one?

 

I believe just the action of engaging 4wd should trigger the blinking light (so technically that should be the 4WD ECU triggering it).

Yes, that front diff switch is identical (same part # and all) as the tcase one.

 

if that’s the case I guess I need to assess the 4wd ecu as well. I don’t get any kind of light when the button is pressed

 

Yea that would seem it could only be the button itself, the wiring from the button to the 4WD ECU, or the 4WD ECU, preventing the light from flashing

 

Pulled the 4wd ecu and don’t see any signs of failure (burns or damaged solders). Additionally, I’m no electrician but is it weird that I get a constant 12 volts at the 4wd button but 0 when it is pressed? To clarify, 12 volts unpressed, 0 volts when pressed. Everything else seems to have continuity where it should. I’m further stumped.

 

I wish I were more of an electrician myself and could help you out. Maybe those smarter than I can answer if thats normal or not

@Dm93
@Strictlytoyz

 

First things first, have you checked for continuity at the 2-4 selector switch yet?

 

I really don't know alot about the 1st gen 4wd system, if this was a 2nd gen I could tell you exactly what to check.

Being we have no light or any action of any kind the first thing I would check is the 4wd fuse, if that's good then check power and ground at the 4wd ECU which looks to live somewhere behind the center console.

The Rear Diff Lock has a separate control ECU on 1st gens (Rear Diff Lock ECU) behind the left kick panel.

 

I just checked the voltage when the switch is pressed. Would I just check continuity at the connector just below the switch?

The 4wd fuse looks good so I guess the issue may lie at the 4wd ecu. It sounds like I just pulled the diff lock ecu to check for damage. The 4wd ecu is the green unit behind the cigarette lighter in the dash I assume? What would I be looking for if I pulled it out?

 

Don't know what color it is but it should have a single 26 pin connector.

Any obvious corrosion or damage, should have Power on Pin 12 (Black/Yellow) and Ground on Pin 25 (White/Black).

Pin 4 (Red) is the selector switch input, it should be grounded when the switch is depressed.

 

If you look at the bottom of the 2nd picture in this post and the top of the 3rd picture, you'll see how to check continuity for the limit switch

 

Ok sweet I’ll give that a go tomorrow.

I see now the switch can be checked all the way at the diff I had been assuming there was a lot in between it.