Question about 1999 Chevrolet Blazer

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99 Blazer put itself into 4 lo and would not switch back into 2wd, indicator lights were flashing

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I found by turning auto off...then hold in the button for 2wd or the desired position... turn the key ON and start the car will cause it to shift to that position.. Flashing means in process of positioning. USADCO

Posted on Jul 17, 2008

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2006 trailblazer indicates 4 lo but is in 2 wheel drive


Switch may be bad. Change switch should fix it.

Mar 13, 2014 | 2006 Chevrolet Trailblazer

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My 1998 Chevy Blazer is stuck in 4hi. It WILL switch to 4Lo, but it will not switch back to 2wd. Any ideas of what might be wrong and how to fix it?


there is a electrical actuator on the transfere case that controls when you put in 4 wheel hi or 4 wheel lo and 2 wheel

Dec 29, 2012 | 1998 Chevrolet Blazer

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I recently purchased a 1999 Chevy Blazer 4WD LT with the 4WD AUTO 4 switch push button. We picked it up cheap. We now know why... 4WD dash switch is dead, changed it with a used one lights flash and n


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..

Apr 21, 2012 | Cars & Trucks

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I have a 1996 chevy blazer and dont know how to disengage from four wheel drive to two wheel drive?


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.

Mar 10, 2010 | 1996 Chevrolet Blazer

1 Answer

2003 blazer will not come out of 4 lo, auto will flash when pressed and then go out


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.

Jan 22, 2010 | 2003 Chevrolet Blazer

1 Answer

1997 Suburban Transfer Case stuck in 4WD Lo


most likely needs an encoder motor. That is the fancy term for the motor that switches the t_case through the gears. The flashing lights indicate a code had been stored and you should have gotten it serviced then before further damage. as long as you dont drive it in 4 wheel you should still be ok

May 10, 2009 | 1997 GMC Suburban

2 Answers

2001 Dodge Durango stuck in 4 wheel-Low. Won't switch back to 2WD


Just to clarify, the "transmission" is not stuck in 4-Lo. It is the "transfer case" that is attached to the transmission that actually engages the 4-Hi and 4-Lo modes. To properly shift your vehicle into 4-Lo, you know that you have to shift the transmission into neutral and slow down to less than 5 mph. Once your vehicle slows down to this range, your can switch your transfer case into 4-Lo mode. Due to the inner workings of the transfer case, the actual shift into 4-Lo may take a few seconds to complete. This is normal and does not signify that there is an issue. All transfer cases that have 4-Lo mode will act this way regardless of the make or model. To make a long story short, to shift out of 4-Lo you must follow the same steps that you took to shift into 4-Lo, just in reverse order. Switch the transfer case to 4-Lo mode if it isn't already there. Slow down to less than 5 mph (your vehicle must be moving, though). Then, shift your car into 4-Hi or 2WD. Give your vehicle several seconds to complete the shift. The transfer case indicator light will flash until it is complete. When it does complete the shift into the new gear mode, you will most likely hear a "clunk" (the range sleeve inside the transfer case disengages from its mating spline) from under your car. Again, any transfer case with 4-Lo (regardless of make or model) will exhibit this same noise. This should help you get out of 4-Lo. It is good practice to shift your car into and out of 4-Lo at least a few times each year to keep all of the splines free of corrosion and build-up. Based on the age of your vehicle, your transfer case may also need a complete flush and some new transmission fluid. Hope this helps.

Feb 22, 2009 | 2001 Dodge Durango

4 Answers

My 98 chevy blazer won't shift into 4wd.


Had the same problem, disconnected the battery for about fifteen minutes, reconnected, 4 wheel drive hi and lo work like a charm now.

Dec 14, 2008 | 1998 Chevrolet Blazer

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