I have a 99 Blazer LS. When i push the 4 Hi button while driving or standing it flashes then returns to 2Hi. I hear the relay behind the glove box clicking but it dosen't go in 4wd. Also, how do you get the dome light to turn off a few seconds after the doors are closed. It only shuts off if I push the Dome Overide button, then it won't come on when I open the doors.

Common for these to need an encoder motor (the electric motor on the transfer case that shifts the transfer case) as it will corrode inside and then no shifting, if it shorts out and draws high amps it will need a transfer case control module (makes the clicking noise, usually behind the kick panel on the passenger side).

ive heard you can try disconnecting the battery for a bit. seems the module will sometimes get whats called logic lock. so ive heard....

if unsucessful, then the encoder as suggested previously.

Have you come up with anything yet? I have the same exact problem with my 98.

I won't have time to work on it until the weekend, but I will be sure to post when I fix the problem. Thanks for all your help.

My friends 98 did the same thing, I seem to recall that the battery had leaked and corroded a wire. Was an easy fix once discovered.

My friends 98 did the same thing, I seem to recall that the battery had leaked and corroded a wire. Was an easy fix once discovered.
The dome light should go out when you turn the key in the ignition.

You never posted what your final fix was?
We are all waiting.... I have had the problem since before Thanksgiving and am considering replacing the vacum switch on top of the transfer case. Seems like $30 dollar part might be worth trying.

I have had this problem for awhile, I've been unhooking the battery for 30mins and it will start working again. If that works then your probably looking for a encoder motor, or a transfer case control module. My mech gave me a procedure for jumping the data connector under the dash to make the module fash the error code on the 4x4 switch. I'll have to post here if I remember.

could you post it please
mine just had the same problem

I have a 95 Jimmy and it is doing the same kind of thing. When I turn the key on but do not start the jimmy I here the switch on the dash click and the light flashes on 2wd and then goes back to 4x4. But I hear a mechanical sound on the transfer case (electric motor sound, like it is trying to engage someting). This first happened during a real cold snap and I have tried the battery disconnect but it did not work. Any suggestions?

Looks like everyone has a similar problem. I too have the light return to 2hi when 4 hi is selected....however, it will go into 4lo only both lights (4lo and 4hi stay on).

Anyone found a definitive solution??????

Bob

Ya I am disappointed with the response to our problem. I thought for sure there would be someone here with the answer.

:smokin:

Good news for me.

I have been posting and scouring this forum as well as others to find a solution to my 4wd problem on a 98 Blazer. I was getting desperate and had an appointment at the local Chevy Dealer ($$$$$$$). Apparently I'm not alone in this matter and others have provided valuable suggestions.

My 4wd quit working in 4HI but would go into 4LO. Plus the lights were doing funny things on the my Selectable 4WD.

Possibilities appeared to be 1) reset computer by disconnecting battery for a time, 2) replace vacuum switch, or worst case, 3) replace encoder motor (parts alone 600 to 700 hundred!)

Hurray! Disconnected battery (positive terminal only) for 30 minutes and it now works like brand new! Thanks to all who have posted on this matter...you've saved my bacon! ($$)

Bob

I encountered the same issue only my '99 was stuck in 4wd Hi and i was 600 miles from home. I ended up replacing the encoder and the module unit for about $1200. The encoder motor is an easy fix to do yourself if you have time and space.

Thanks for your input. It's been nearly a month now and the re-power (re-boot) fix seems to be holding.

Well it's been a while since I posted the message and I checked back regularly then sort of forgot about it until now. I still haven't replaced anything yet but tried to disconnect the battery, It switched to 4Hi afterwards but sometimes it works and sometimes it dosen't "wasn't really a fix, It's always been that way". Once I figure out the problem I'll be sure to post it.

I have the same problem on my 98 blazer. the dealer diagnosed that the encoder motor was gone quoted $550 to replace.I replaced it no fix.I will try some of the other things suggested hopfully we alll find the problem and are 4wheeling again.

P.S : the dealer price for the motor alone was $440, I found a web site that sold OEM parts cheeper. I paid $299 for the same exact part. This part has no aftermarket replacement this is a genuine OEM part.Same box and label as on the dealers. 1Aauto.com

Good luck to all

so i am understanding ther is only 3 things this could be. battery, vac switch, and encoder motor.
i here the motor working and it will go into low range but here is a good one. i lifted the front end after putting it in low and the front tires will turn. not at the same time. if it is going in low with a bliking light and it will act like its in low then why wont the front lock into 4wd?
but i will try the batt. thing.
can anyone explain that?

fiberspider

the batt thing didnt work. but here is one better. I can’t find the vacuum switch. so I got looking for the vac. line. well I found a hose off. look on the fire wall under the hood in the middle. there is a black part with a blue electrical connector. this has 2 hoses. well check that. as well I encourage you to look at all the hoses they get brittle.
fiberspider

Check these two items out.


--- Under the Battery Tray is a vacuum actuator. This engages the front differential. Best way to see if it works is to do this - Look at the center-top of your firewall, you will see 2 vacuum hoses coming off a switch. Take these off, and connect them together, just holding them will do. If the actuator opens,closes, then that is working well.

--- If the actuator is working, then the peice that you took the 2 vacuum hoses off, is usually what is bad. For a cheap fix, Get a hose fem/fem hose coupler, usually $.25


Hope this helps.

Have you come up with anything yet? I have the same exact problem with my 98.


I had the problem with my 98 LT, bad transfer case motor was the problem!

Hi,
I have a 97 Blazer LT. Same prob, press 4HI or 4LO, even at very low speeds, lights, and goes back to 2HI. Can hear clicking from module in dash.
4WD worked fine last Winter. All started when I tried to activate 4HI while driving on muddy and watery dirt roads in a Wildlife Management Zone. FOUND THE PROBLEM TODAY a week after. Fuse #22 "4WD" a 20AMP was blown. Switch must have got wet or something.
Replaced it, road tested for 30 mins, 4HI, 4LO, and back to 2HI multiple times. IT'S FIXED!!!
Even my mechanic was stunned!!! Oz :evillol:
P.S. Total Repair Cost $000.00 (there was a spare on the fusebox door) A unscrupulous SOB would have changed a few things, you know what, and not even kissed me :nono: .

I had same problem, will go into 4LO and 2HI, but no 4HI. Disconnected negative battery cable for 30 minutes... Bingo works again. Thanks to all....