2000 Blazer LT 4.3L 4 door 4wd won't engage

Greetings to all. My first post.
Our blazer has 190,000 km (about 115,000 miles).
3 Button dash control.
Transmission was rebuilt at 100,000 miles (main troque converter spline was shot)

The 4 wd will not engage in either hi or lo.

whether moving or not, press 4 wd lo, light stays on. but nothing happens.
I cannot hear the transfer case engaging.

Had a previous problem, (withflashing light): found the vaccum hose under battery case was worn through.

I do have a service engine light on the dash.
This may be unrelated, because 4wd stopped working long before service engine light came on. I have changed the Oxygen sensor, but no reset the fault yet.

Need to know where to start.

Mike D Dolson

Do the lights on the switch stay on solid when you select a range, or do they flash and then return to 2 HI?

They STAY ON solid.

Mike D

Do the lights on the switch stay on solid when you select a range, or do they flash and then return to 2 HI?

are ALL the lights on? It would also be helpful to scan for codes. Something to check would be the connector at the transfer case shift control module. It's down by the passanger side floor, right side behind the panel between the dash and foor. Disconnect it and inspected for water damage (green, corroded) if it is the module will need replaced and connector repaired. If not, you may still need a module.

No all lights are NOT on. Just the selected mode ie 4 W-Hi.
I do not have equipment to perform a scan.

I am out of town working right now, I will check control module this weekend.
I did some looking but just to be sure where I'm looking: right side of passenger side, & the panel in the right side wall (ahead of door) ?

see attached jpg (I assume this is the item I'm looking for)

Thanks

Mike D


are ALL the lights on? It would also be helpful to scan for codes. Something to check would be the connector at the transfer case shift control module. It's down by the passanger side floor, right side behind the panel between the dash and foor. Disconnect it and inspected for water damage (green, corroded) if it is the module will need replaced and connector repaired. If not, you may still need a module.

Thats it, ahead of the door.

With the engine at idle, check for vacuum at this switch. One of the lines should have vacuum:

http://i561.photobucket.com/albums/ss58/cwhook/600-10419994WDaxleactuator.jpg

http://www.dormanproducts.com/p-15949-600-104.aspx

It's located on the firewall, just above the distributor. The other line goes to the actuator under the battery and should have vacuum when 4WD is selected.

Sorry for delay in getting back. I will not be able to check the vehicle until next weekend (Dec10,11) as I am still out of town on assignment.

Thats it, ahead of the door.

I could not find the the transfer case shift control module.
There is no access panel on the right side of the passenger compartment. There is just a smooth plastic panel covering the entire wall below the dash & ahead of the door.
Thought I'd better get more information before I start ripping things apart.

Mike D

Just call me stupid & get it over with. I was expecting to find an access cover.
I looked around and found acouple of photos.
I now know I should have removed the kick panel to reveal the module.
Dope! ( feel like Homer Simpson now).

I'm sorry for the late reply.
I finally got around to pulling the transfer case shift control module.
as you advised the bottom two pins were corroded.

I cleaned the contacts, & pins, & put a slight kink/bend in the pins to improve contact pressure. Plugged it back together, bolted it in & presto I have 4WD again.

Thanks to all who offered advise.

Of course my (known) weak battery finally died while had the door open/dome light on, & had to be replaced. But it was due (6 years old).

Mike Dolson

Glad to hear it's taken care of.

Do the lights on the switch stay on solid when you select a range, or do they flash and then return to 2 HI?
What is the solution when they flash, 4wd doesn't engage and then the switch return to 2hi?

What is the solution when they flash, 4wd doesn't engage and then the switch return to 2hi?

This is exactly the situation I had, at an earlier time.
Turned out to be a broken vacuum line that routed under the battery holder.
It took a couple of hours to find that one.
Mike D