I have a 2003 chevy blazer LS, 2-door 4wd w/ vortec engine. The 4wd is activated by a 3-button switch on the dash (2wd-hi, 4wd-hi, 4wd-lo). The problem is I can't get it to go into 4wd-hi no matter what I do. When I shift into 2wd-hi or 4wd-lo the switches light up momentarily and I can hear a clicking sound from under the dash behind the glove box, and then the transfer case goes into these gears just fine. But when I punch the 4wd-hi button, nothing happens. No light, no clicking noise from under the dash -- nothing, it just won't go into gear, it stays in 2wd-hi. Help!
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https://www.youtube.com/watch?v=IP0jhBG0jv4
Jun 30, 2012 - Uploaded by Mark Jenkins
How to Diagnose and Repair Chevy Blazer and GMC Jimmy 4WD\ 4x4 Issues .... The transfer case either doesn't want to engage, or it gets stuck in 4 lo. ... my s10 4x4, I watch your videos and I start to work on my truck,I start ...
? 9:02
https://www.youtube.com/watch?v=stooGR4BcjE
Mar 2, 2012 - Uploaded by 1A Auto Parts
I have a 1996 chevy blazer ls...my 4 wheel drive stoppedworking. ... 4l and I hear the click underneath me, but that's it..itdoesn't engage, but the ... I have a 2003 gmc Sonoma and when I put it into 4 high it feels like it does
Sounds like the encoder switch is bad ..it on the transfer case .it has a motor with wires going to it.when you press the button it sends a signal to that motor to switch into a certain gear..
take the switches 2wd 4wd hi 4wd lo out of the dash and unplug them all then use small wire to jump the 2wd connectors then replace new 4wd button and new 2wd button
As I recall the 96 blazer had electronic shifting for 2wd to 4wd. There should be a small panel on the drivers dash buttons for 2wd, 4wd lo and 4wd hi.
Simply press the desired button while stationary and if the system is functioning properly then it will shift and the light for the engaged type of drive will be lighted. Generally you would like to be in 2wd for this vehicle.
Check the fuse to your 4wd at the fuse panel at the end of the dash drivers side. If the fuse is good, put the transmission in neutral and listen for the Transfer case encoder motor to work when you push the button on the dash for 4wd hi then to 2wd. If you do not hear it working, inspect the wire harness at the Encoder motor to make sure there not damaged in anyway due to corrosion or disconnected.
Here's some info on how the 4wd system operates on newer Blazers for all those searching for the cause of the flashing dash switch light and no engagement.
4WD System Operation on 98 up (2nd Generation) Blazers/Jimmies
The front drive shaft always turns on “shift on the fly” systems so the drive train is at the same speed in the front as the rear or the whole thing would break when engaging 4Hi or Autotrac when moving. InstaTrac (NV243 case or NP1) has 3 buttons. AutoTrac (NV246 case or NP8) has 4 buttons and clutch packs in the transfer case and is the only system for on pavement driving! Prior were the NV231 (87-93) lever and NP233 (94-97) electric motor. Your VIN # is the only sure way the dealer can get correct parts/listings! 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, just make sure you turn off your radio first. 5. Still not working – take it to the dealer and stop at the bank on the way for $$$$! 12577412 is the part number for the Transfer Case Control Module (TCCM), or you can do the Salvage Yard for $15.00 if that's the part that has gone bad.
i have a 1993 blazer 4.3 w code 4x4 with a 4L60 E . my truck wouldn;t go in 4 hi or low. so i changed the transfer case motor and it works fine now. If you turn the ignition key to on but not crank the engine and open the driver door and push 4 hi button, you should hear the transfer case motor cycle for 3 or 4 seconds every time you push button and the light will flash until it goes in 4wd If the 4 hi button light doesn't flash during cycle then it could be a bad switch. if the transfer case motor won't cycle it could be a fuse or a bad transfer case motor . Hope this answers your question. pgale89
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