Four wheel drive will not engage?

BWARD42

MEMBER
1999 CHEVROLET SILVERADO
4.8L
V8
4WD
AUTOMATIC
150,000 MILES

When you pull the selector lever into four-wheel hi, the light on the dash does not come on, the actuator does not engage the front end, all fuses have been checked. I replaced electronic shift switch on the transfer case, replace the actuator with a brand new one and left it dangle under the truck while trying to shift in the four wheel drive still the actuator did nothing and I still do not have the light on the dash. I’m at a loss. I have a Haynes manual but there’s nothing really for a manual transfer case.

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,513 POSTS

It sounds like it maybe the controller. can you hear the actuator working? If not let remove the actuator then work the control to see if it moves this will let us know if the problem is internal. Here are the wiring diagrams so you can see how the system works. We should check the ATC, IGN1 and 4WD fuses this guide can help with the fuse locations below.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.

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Sunday, January 17th, 2021 AT 6:20 PM

BWARD42

MEMBER
4 POSTS

Thanks for the reply. No, there is nothing happening to the actuator. To be sure of this I hooked a brand new one up and left it out where I could see it from under the truck, had my boy switch in and out of 4 hi and 4 low. I replaced the switch on the transfer case thinking that was the issue once the new actuator didn’t work. I ran a multimeter on all the fuses already and power was good.

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Monday, January 18th, 2021 AT 4:47 AM

KEN L

MASTER CERTIFIED MECHANIC
47,513 POSTS

The control modules go out on these as well. Let's use the wiring diagrams above to confirm the connections are all good, (power and grounds as well) then replace the module here are instructions in the diagrams below. To the left of the instrument cluster behind the headlamp switch. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.

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Monday, January 18th, 2021 AT 6:29 PM

BWARD42

MEMBER
4 POSTS

I didn’t realize there was a control module for the manual transfer case, I see it for the electric transfer case but in the wiring for manual I don’t see it. I am having the wiring checked again to see if I missed anything. The above wiring you posted is for electric.

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Tuesday, January 19th, 2021 AT 1:27 AM

KEN L

MASTER CERTIFIED MECHANIC
47,513 POSTS

Here are the manual transfer case wiring diagrams. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

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