Switch on dash when pressed on 4hi or auto only flashes you can hear transfere case engaging ,when pressed for 4wd low light flashing no power to front axle in all cases is front axle actuator vacum controlled?
Re: my 2000 blazer won,t select 4wd hi/low or auto
Most likely it is a ripped vacuum actuator located under the batter tray. Oil tends to be sucked through the vacuum lines and into the actuator, in turn it ruins the actuator that normally pulls on the shift cable. Reccomend also replacing the vacuum switch on top of the transfer case that is the culprit of oil being sucked through the lines. Good luck!
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Check connection at the 4X4 control module , check power and grounds . Do you know how to do basic electrical testing ? Does your truck have manual or automatic trans mission ? Which transfer case does yours have ?
The NVG 263 transfer case features a three button shift control switch located on the instrument panel. When the ignition is in the RUN position, the transfer case shift control module (TCCM) starts monitoring the transfer case shift control switch to determine if the driver desires a new mode/gear position. At a single press of the transfer case shift control switch, the lamp of the new desired position begins flashing to inform the driver that the TCCM has received the request for a new mode/gear position. The lamp continues to flash until all shifting criteria has been met and the new mode/gear position has been engaged. Once the new mode/gear position is fully active, the switch indicator for the new position remains ON constantly. In the event that the TCCM can not or will not complete the shift, the indicator returns to the previously selected position; this is a Transfer Case Shift Control Switch Indicator Flashes, then Returns to Previous Mode condition.
The NVG 263 transfer case provides the driver with 4 manual mode/gear positions:
• 2HI - 2 Wheel Drive high range
• 4HI - 4 Wheel Drive high range
• 4LO - 4 Wheel Drive low range
Have it check for DTC'S - diagnostic trouble codes ?
If you can't get 4 high, then you can't get 4 low either. You can get the transfer case to go into 4 low, but unless the front axle is engaged, you will still be in 2 wheel drive. There is a vacuum switch that engages the right front wheel. The left wheel is engaged full time. On earlier models, this vacuum switch is located unerneath the battery tray. It is prone to become disconnected from the vacuum line. Check this and all other vacuum lines that are connected to the 4wd system. The way I test my 4wd Jimmy is to find a dirt or gravel road or parking lot and accelerate hard from a standing start in both 4hi and 4lo. If 4wd is not engaged your back wheels will spin.
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.
yea its not shifting again like before ? sounds like your transfer case solonoid has possably gone bad again .. these are a sometimes dont work item .. It is what shifts the transfer case into gear and it might be a little worn or weathered and not letting the switch kick it in gear all the way from the N position. thanks Jerry holler if you need more.
These trucks are famous for the transfer case control module failing and causing problems like you are experiencing. The module is usually located in the passenger foot well kick panel. You should be able to find it easy since that is what is making the clicking noise when you try to go into 4x4. When you find it-unplug the 2 connectors and looks for green corrosion on the terminals in the plug and also on the module. They are famous for water intrusion thru the heater system. If you find corrosion, terminals in the connectors will need to be replaced as well as a new module(they are expensive).