Four-wheel drive not working?

1997 GMC SIERRA

200,000 MILES • 5.7L • V8 • 4WD • AUTOMATIC

EXTCABZ71

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When 4high is pushed, light just blinks, when I push 4 low light continues to blink but it does shift into low range. I replaced the push button switch, which didn't work, then I replaced the actuator, no luck. I took the original actuator to a friend's and plugged it into his truck, and it works fine, when I plug mine in with the 4H light it makes a noise that sounds like a fan. Any help is appreciated.

Video (Click to enlarge)

Jan 7, 2023 at 12:29 PM

STRAILER

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53,854 POSTS

Thanks for the video, it helps. It sounds like a ground is not working. let's check the ground wire #119 which is at the right front of the engine. Also, we should check the fuses that run the system for power in the interior fuse panel, #2, 34, 16 and 4.

This guide can help:

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

Here are the transferase and actuators wiring diagrams so you can see how the system works and the fuses location as well.

This guide can help you check the ground:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the images (below). Please let us know what happens.

Images (Click to enlarge)

Jan 8, 2023 at 7:13 PM

EXTCABZ71

MEMBER
2 POSTS

Okay, I checked the fuses, and they are okay, took ground on passenger side of motor to frame off and wire brushed, checked continuity from motor to frame, body, and battery, every reading was .01 to. 02 ohms, then checked battery voltage, was 12.6v, turned on 4H and checked voltage from ground terminal to positive terminal, had 10.6v, checked positive terminal to frame and had 10.6.

Jan 11, 2023 at 3:51 PM

STRAILER

CERTIFIED EXPERT
53,854 POSTS

I am wondering if the transfer case control relay is causing the problem, here is the location. Check out the images (below). Please let us know what happens.

Image (Click to enlarge)

Jan 12, 2023 at 10:35 AM