93 4.3 no 4x4 hi

[ajcndjg]

I have a 93 Blazer with a 4.3 with electronic 4wd selection. my problem is it worked great for the past week now i can only get it in 4 low and not 4 high. If i crawl under the transfer case and push the button it sounds like it wants to engage but it wont. also when you push the button while you drive it does nothing now it must be i neutral to get the button lights to flash then they go out? Again I have low but no high any ideas?

[Mikado14]

Since you have low but no high, that would rule out the vacuum circuit for the front axle. It appears that the encoder motor is on the fritz.

You can remove the encoder motor and see if it is moving when you select 4Hi or 4Lo. Your looking for complete and smooth travel.

However, there are the fuses. One fuse goes to the switch and the TCCM and is ignition connection B. The other is the horn/dim fuse. Check these first.

[ajcndjg]

thanks ill give a try how much time would you say is involved in pulling that motor out, i'm a pretty decent mech. im trying to get an idea. Thanks again.

[s10bajadan]

sounds like the encoder shifter motor.
I just did one on my 92 blazer. Disconect shaft at transfer case and move to the side. I belive is 3 10mm bolts holding the motor the the t-case and 8mm bolt on the harnes. The motor should slide past the front out-put shaft yoke when removed.
PLEASE NOTE !! if you engage the coder motor while its off the t-case IT WILL BE JUNK!
best price I found was 199.99 at ADVANCED AUTO PARTS.
GOOD LUCK.

[ajcndjg]

why will it be junk? I mean does it keep running or does it have to be timed with the transfer case or what? I'm ready to yank it but I want to yank it to see if its working. So how do you tell if its working? Does anyone know where to find an internal schematic of this thing? like a breakdown or microfiche? Or could something just not be meshing right? ANYONE HELP?

[s10bajadan]

I dont know the reason in tech. terms but Im told dont switch the motor when its off the t-case.

Befor I replaced my shifter motor it was getting stuck in 4hi and 4low.when I pulled the shifter motor off it was all corroded where the t-case and motor meet. The plactic cover that houses the shifter gear was all buckeled out . When I looked in side where it shifts it was all striped out from all the corrosion pushing the shifter gear away from the t-case. That being said ,pull the dam thing out and look at it. Put a wrench on the t-case shifter nub that is sticking out. make sure its not bound in the t-case . shift it into 2h with the wrench . you know your in 2h when the yoke spins free. If you replace the decoder motor make sure its in 2h when you bolt the new one on.
good luck!

[ajcndjg]

well i found a site that was a big help i pulled the tccm fuse for a while put it back in and it worked now to see if it keeps working! the site said something about 4x4 codes and connecting a jumper from "A" to "J" on the Data link below the dash but I can't figure which one is "J" if anyone knows about this let me know. Check this site out incase you havn't already it helped me lots of good info. www.s10blazers.com

[s10bajadan]

88 to 93 dont store codes. 94 and up do. If you pulled the fuse on the TCCM and now its working great. The relay may have been stuck. If it starts acting up try going to the bone-yard and getting a TCCM. should be about $20.00.
If its still giving you problem REPLACE THE DECODER MOTOR !

[ajcndjg]

Thanks for the advise. But since it works now it doesnt flash when I hit the 4HI button it just lights up and goes right in is that bad or good?

[s10bajadan]

When you first turn the key on both (4Hi & 4Low) should light up for a few seconds and go off.
Is that happening ?
If not you may have a bad dash switch,or light in switch is burnt out.
If it does light up the the dash switch/bulbs are good.
The decoder-shifter-motor shifts the T-case and aslo reports what mode its in ( 2HI ,4Hi, 4Low).
You could run it like it is and see what happens ,but I would hate to have it start swrewing up again when we have a foot of snow.
I would replace the Decoder-Shifter-Motor.