Four-wheel drive not working

THOMILLIP45

MEMBER
1997 CHEVROLET 1500
5.7L
V8
4WD
AUTOMATIC
160,000 MILES

(Auto 4-wheel drive)

1) Four-wheel drive stopped working last year.
2) Fixed 4-wheel drive by replacing front differential actuator.
3) This year 4x4 working until 1 day before 10-inch snowfall (I have a 1/3-mile-long gravel driveway).
4) Only in Neutral when I press any of the three options on the 4x4 switch, both 4 high and low indicators blink and then stay on (nothing from the 2wd indicator).
5) Replaced Transfer case motor/Actuator with the same results.
6) Got a warranty exchange for the front actuator and replaced that as well as the 4x4 switch on the dash. Same results. All fuses are functional.
7) Cannot locate wiring diagrams for the 4x4 controls, only snippets. Help?

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

You are correct that the most likely cause of this is the encoder/actuator but if you replaced that and it still does not operate then we need to dig further.

Also, when you press the button to change position and the two lights flash, that is telling you that you are not getting communication with either the module or the module is not able to complete the shift.

The first thing to do is check for codes as that will help. Even though the check engine light is not on, you may still have an issue.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes then we need to go to the transfer case module on the steering column bracket and check voltage input from the button, and then output to the actuator.

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

If you have no voltage going out, then you need to check the other various inputs to the module like the park neutral switch and the relay.

Basically, if you have everything coming into the module but still no output then you have a module issue.

Please run through this info and let me know what questions you have. The wiring diagrams are below.

Thanks

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Four-wheel drive not working

1 Reply

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