2000 blazer transfer

[gametrail]

I cant get the 4x4 on my 2000 blazer to kick in?

[FishFind]

do you hear any noise when you push the button?? Do you see any of the lights blink.

Please be more descriptive of what is happening.

[gametrail]

Sorry the light comes on put I dont hear anything. I was told that it had a little electric motor I should hear. Is that right?

[FishFind]

yes its called a encoder motor and it is under the drivers side on the transfer case. Roll down your window and see if you hear it. What do the lights do on the selector switch?? blink and go back to 2wd? Also put it in neutral and try and select 4hi or 4lo.

Just because you don't hear it does not mean it is not working. You can test it by jacking just the front passenger tire off the ground. Go and spin the tire it should spin free. Then go and start the truck and push 4hi wait for the light to turn solid on the switch and then go and see if the tire still spins. The truck must be running because it is a vacuum actuated 4x4. If the engine is off it will not engage.

For the 4lo the truck needs to move a few feet for it to engage. So if you want to test that you will need to drive 20 feet or so in 4lo and then leave engine running and do the same test.

[FishFind]

Here is a post from Muddog321

1. Select mode on dash switch
2. Signal goes to the Transfer case control module (TCCM) or computer located in the cab on the passenger side behind the kick panel.
3. If you want 4 Lo the TCCM commands the encoder motor on the transfer case to switch a lower gear in (requires putting the shifter in Neutral and be stopped or only going 2-3mph). Note that if 4 Hi selected no action done in the transfer case. The transfer case is chain coupled and has the low and high gear. You can put all systems into Neutral by pushing the 2Hi and 4Lo button at the same time when the key is in the run position (or running but not off or acc).
4. The left front (drivers side) CV axle is always engaged to the front differential, but the right side is not coupled in 2wd. There is an actuator located under the battery tray that when commanded is vacuum actuated and pulls a cable from it to the right side CV axle coupler engaging that axle. A sensor is on that axle that tells the TCCM the axle position.
5. On 99up there is an additional vacuum switch on the firewall that switches the vacuum on and signals the TCCM also.
6. The dash light on the selector switch flashes while all this is occurring and will not switch out of 2wd unless all parts report correctly – same on the switch to any mode or back to 2wd.

So, there are a lot of possible failure areas with actuators/computer/motor/sensors/vac hoses and a special scanner is required to read the codes when the Service 4WD light comes on. But, a few things can easily be done before going to the dealer.
1. Check all vacuum hoses from the intake to the drivers side reservoir can, then to the extra switch (99up) and down to the under battery actuator. Small hose is 5/32 and larger is 7/32”.
2. See if the actuator pulls the front axle cable to engage it. If not and all hoses are good the diaphragm may be leaking on the actuator. If it engages but the light is still flashing remove the indicator switch on the front axle (only electrical plug in there) and manually push it in with the connector plugged in and see if the light stops, if so replace.
3. Listen to the encoder motor clunk when 4 Lo selected. If not working look at the wiring going to it for any cuts/breaks and repair if any found. Another indicator switch on top of this case. The fluid in the AutoTrac case should be the newer light blue Autotrak –II synthetic P/N 12378508 ($7 qt) not the red Dexron III.
4. If the light keeps flashing after this then disconnect the battery for 30 minutes for a TCCM reset.
5. Still not working – take it to the dealer and stop at the bank on the way for $$$$!


Here is a link to the thread. http://www.automotiveforums.com/vbul...ghlight=blazer