hey guys, i am new here. i just bought a 94 s10 blazer 4wd. it has the electronic 4wd. when i try to select 4wd high nothing happens.. the only way i can get 4wd is if i stop put the truck in neutral and select 4wd low. when i do this both lights flash and 4wd low works. when i first got the truck i was able to drive and select 4wd high if i needed the extra traction.. now it is impossible to get into 4wd high. please help.

 

From what I have researched on the electronic 4x4 and the threads here, your TCCM may have a stored fault code in it memory. There are also other things that can cause this like a bad vacuum switch on the drivers side of the transfer case. This switch controls the vacuum that is routed to your front drive actuator (under battery box) from the intake manifold and the vacuum controls for the heater/ac. You could have a bad vacuum actuator, bad encoder but since it goes into 4LO thatmay not beit.A bad TCCM under the dash, bad connection/wire to the TCCM. Bad vacuum lines from the manifold or to the acuator under the battery box.

If you search this forum you will find how to check the TCCM for codes...

 

hmmm.. tccm?? so i have to have a code reader to clear those codes? i will check all the vaccum lines and hopefully i can solve the problem. is there anything else it might be.. i bought the chiltons manual and it is worthless.. im glad experience is better.. thanks guys. keep the suggestions comming..

 

'94 is pre OBDII so you will have a hard time finding an inexpensive scanner. Try searching the internet for OBDI there should be some open source resources for you. I do know that AutoXray makes a scanner for that year but they run over $199+. Also you can check E-bay for a scanner...

The '94-'95 years are not considered standard years...these years was when GM was doing a lot of changes to the emissions systems and the electronics...

 

In the meantime you can try disconnecting and reconnecting your battery.

 

how do i know if the acuator is good.. all the vacuum lines are good no holes...

 

OK, i went down to the auto parts store and bought some new vacuum hose. i replaced most of the hoses routing to the actuator. nothing happened. 4x4 high still wont work. no luck there.. what are the chances that i have a bad vacuum switch? does anyone know how to test it?? please advise..
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