93 Jimmy 4x4 problem..

[93Jimmy]

I am new to this board & I just purchased a 1993 GMC Jimmy 4x4 it has a 2 button switch that has 4 hi & 4 low according to my owners manual is states I should be able to switch to 4 hi while driving & 4 low when I stop & put the truck into neutral well when I try to switch to 4 hi nothing happens. If I stop & put the truck in neutral & switch into 4 hi both lights blink a few times then go out, I hear a "click" sound under the pass. side dash if i do this a few times both lights will stay on but the truck is still in 2 wheel drive. now if I switch into 4 low I hear the transfer case engage into gear under the truck although both lights do stay on most times 4 wheel low does work (sometimes only the bottom amber light stays on)
I never hear anything from the transfer case when I try to engage 4 hi. I heard that it may be the neutral safety switch?? I do have to push up on my shifter when putting it in neutral because it's a little sloppy, also it is hard to get it into park it's like the linkage may need adjusted. Please help!! It's starting to snow!

[JaVeRo]

The first thing would be to verify that the transfer case is NOT engaging in 4hi. With the engine running, transmission in neutral, shift to 4hi. Ignore the lights, block the wheels, reach underneath and try to turn the front driveshaft. If it turns freely then you are correct, the transfer case is not engaging. If it is locked then the problem is with the front differential. The lights will not show 4hi until the front differential is engaged.

Post back the results.

James

[93Jimmy]

James,

I did what you said (although I had to press the button a few times to get the lights to stay on) & it turns freely so the transfer case is not engaging. what do you think my problem is? I talked to a guy at work who has a 94 Blazer & he is having the same problems, he said he unhooks his battery for a while & then 4 HI works one time until he does this again something about clearing the codes. I haven't tried this.

[JaVeRo]

That's the part I know nothing about. All of my problems have led to the front axle or actuator. Sorry I couldn't help.

Follow the post by ChevyMan, you may find what you need.

James

[93Jimmy]

OK, I have been doing some stuff to my truck & here is where I stand, I replaced the transfer case motor & vacuum switch on top of the transfer case (even though my boss @ work who owns a 95 Blazer & has the same problems as me had already done this with no fix) & it didn't fix my problem. My wife took it to work the other day & the service engine soon light came on so I took the neg. cable off the battery for a bit to reset the computer, this worked for the SES light. I took the truck out this morning to see if the 4x4 worked & it did! I hit the 4hi button & it went right in 1st try but when I turn off the truck it don't work again. Now if I remove the neg battery cable It works as long as I don't turn off the truck. I am going to install a 12v Battery Disconnect Switch for a quick fix until I can track the problem down.

Can it be my natural safety switch? Others have said the computer control for the 4x4, but if this is the case wouldn't the 4x4 just plain quit & never work? Is there a relay that may have gone out?? All my vacuum lines are in good shape.

Please someone HELP the snow just keeps coming!!

Here is a link to the switch I want to install: http://www.dxengineering.com/Parts.a...rtNo=DXE-G1432

I can just turn this off when I turn the truck off & turn it on before I start it again. (beats removing the cable every time)

[jamack1]

I would try going to a local junk yard and getting the 4 X 4 control module. I believe that this module is monted to the ECM holding bracket. It should be located behind the passengers side dash. The 4 x 4 control module is a gray steel box, that can be removed fairly easy. It's just a plug and play type design. Unplug the old one and install the used one. This may help with the problem.

[93Jimmy]

Here is a pic of the switch mounted

I got the switch mounted & it works like a charm! I just shut it off when I know I am going to be needing the 4 wheel drive. I mounted it in the cab under the dash so it is easy to get to. I tell ya it's a cheap easy fix. I will be out lookin for a control module when the weather breaks.

[muddog321]

What you are doing is resetting/rebooting the 4wd little computer called the TCCM with the power disconnects and 30 min is the norm, so check the connector on it and if the pins are loose or corroded fix them. You also have a sensor on the fornt axle and then the actuator under the battery.

[93Jimmy]

Originally Posted by muddog321

What you are doing is resetting/rebooting the 4wd little computer called the TCCM with the power disconnects and 30 min is the norm, so check the connector on it and if the pins are loose or corroded fix them. You also have a sensor on the fornt axle and then the actuator under the battery.

Where is the ECCM located? I just got this truck & I have no clue where anything is.