2000 blazer wont go into 4wd

Asked by Sep 14, 2016 at 03:44 PM about the 2000 Chevrolet Blazer LT 4-Door 4WD

Question type: Maintenance & Repair

i push the 4hi but it just blinks and goes back to 2hi...i hear
a click down under the vehicle by the encoder motor when i
push the button and a click when it goes back to 2hi...my
vacuum shift actuator thats located under my battery
squeezes down all the way like it should...my front vacuum
actuator solenoid valve located in the engine bay on the
firewall in the middle, the bottom hose is sucking in air
when in 2hi when i unplug the hose and put my finger on
it...thanks for your help!

15 Answers


Make sure your connection on the buttons has good contact, might be loose... I had to put a piece of paper to wedge it tighter in the plug on mine then worked like a champ.... Won't take but two minutes so it's worth a try...

what about if i put a ziptie around it? would that work better?


You may still need an encoder motor. Sometimes when they fail this way. The "stop" switch in the motor doesn't work anymore and it swipes through the range and just goes back. Or its too weak to really move, it sounds like it does but it doesnt.

it broke when i was using it like 2yrs ago...should i hear a noise coming from my control module thats on the passenger side kick panel? bc i dont think it makes a noise


It typically sounds like a relay clicking

this from a different forum i was reading on here.......now we know the possible problems lets check them individualy fist the encoder motor when your in nutral and press the 4hi button does it flash and just never go in? can you hear an electric motor? after you press 4hi get undernieth the blazer and check if you can turn the front drive shaft by hand? in not this is a good thing and means your transfercase is locked in four wheel drive. if you can turn the drive shaft by hand i would replace the encodermotor........okay now should i try having all 4 tires on the ground and have the truck in neutral and see if i can turn the front drive shaft by hand? and then try putting it in 4hi and try spinning the drive shaft by hand? and if the drive shaft spins i need a new encoder motor? bc in 2wd neutral it should spin and 4wd neutral it shouldn't spin right?

i think my solenoid/vacuum actuator are good


I never tried any of those test out. Other than its my understanding the light can not come on until the circuit is closed when the encoder motor get it in 4wd. and since it goes back to 2wd, then its not going into 4wd. Will it also not go into 4wd low? then the encoder motor is not working.

yes will not got into 4wd low and auto 4wd so you're thinking it's the encoder motor? is there a way to test it and see if its the reason?


I know they cost to much to replace if they are not bad. Remove the passenger side kick panel and disconnect the TCCM. Inspect the electrical connections for corrosion. Clean/replace as necessary. A corroded TCCM connection can cause a code for the encoder to be set too. :::Copy & Paste:::Youtube Remanufactured Transfer Case Control Module


Look at that video and check those connections and clean if they are corroded.

2 people found this helpful.

Another video youtube:::How to Diagnose and Repair Chevy Blazer and GMC Jimmy 4WD \ 4x4 Issues

1 people found this helpful.

The TCCM (transfer case control module) has all power and ground connections. I read that you can get diagnostic codes out of the TCCM by grounding pin 13 of the OBD connector under the steering wheel. Pin 13 is the pin use use to ground to check codes. If you did indeed ground #13 the 4wd light will blink Code "1" is "RAM standby power" and is considered normal, may be caused by clearing the codes. Code "2" is "Encoder fault" Code "3" is "TCCM motor circuit" Code "4" is "RAM/ROM failure" Ground pin 13 at the data connector under the dash. The lights on the switch should flash. You are only going to have a choice of 4 codes as mentioned above. Here is the procedure to further clarify. Diagnostic Trouble Code (DTC) Displaying: The transfer case shift control module is equipped with the ability to store diagnostic information, which is useful to a technician in the event of module, component or wiring failures. This information can be retrieved from the transfer case shift control module by way of flash codes, which are displayed on the three transfer case shift control switch buttons. These buttons are located on the instrument panel to the right of the steering wheel Before obtaining DTCs, perform the following transfer case control module (TCCM) Self-Test. TCCM Self-Test Observe the transfer case shift control switch indicators while turning the ignition switch to RUN. A properly operating system will flash all indicators and then will return to the current gear. If the system is operating normally, then proceed to Displaying Codes. If the TCCM failed the Self-Test, then test the following circuits. • Battery Positive Voltage, and Ignition Voltage for battery voltage • Ground Circuit for ground • Diagnostic enable circuit for an open or high resistance • Transfer case shift control switch connector If the above circuits are normal but the TCCM still fails the Self-Test, replace the TCCM. DTC Displaying Turn OFF the ignition for 10 seconds. Connect PIN 13 on the data link cable (DLC) to a ground. The DLC is located in the cab under the instrument panel on the driver's side. Turn ON the ignition, with the engine OFF. Observe the transfer case shift control switch select buttons for flashing codes. Refer to Diagnostic Trouble Code (DTC) List above. Important: If the transfer case shift control switch buttons all blink only once and then stop, no fault codes are stored in the transfer case shift control module. • When one DTC is stored in memory, that code will blink that number of times followed by a 3 second pause and then repeat. • If more than one code is stored, the first code will blink, followed by a 3 second pause and then the second code will blink. • This sequence will continue until PIN 13 on the DLC is no longer grounded. • If the TCCM will not communicate the presence or absence of DTCs, test the above circuits in Self-Test Step 2. If the circuits are complete, then replace the TCCM. Here is a break down of your 4WD system::D 1) let's start off with the easy things -- have you checked your fuses? Don't assume that just because the fuses are labeled 4WD that they are the only ones for your 4WD system! Fuse 10 (on the Jimmy/Blazer) is for the courtesy lights but guess what? It also controls the logic side of the TCCM (+5VDC). Pin 6 (thinner orange wire) should produce +5VDC and should be HOT AT ALL TIMES (meaning you should be able to read +5VDC on the line anytime, key on or off). The two large orange wires are your +12VDC lines and are controlled from the 10A fuse located in spot #15. Check your LARGE orange wires as you are getting +5VDC logic as the lights are coming on on the dash. The +12VDC is used for the encoder motor, check to make sure you have +12VDC at both the large orange wires (they are right beside each other, and there are two large black wires beside them that are ground). Notes: All black wires are ground -- all orange wires are power (hot). There is a 10A fuse (#15) for the 4WD system, located in the fuse panel. There is a 20A fuse, located under the hood, that is also for the 4WD system (I'll have to look up the fuse number). The 4WD system also pulls from the 10A courtesy lamp fuse (#10). 2) The vacuum switch (located on the firewall http://www.kylestubbins.com/files/bl...uum_switch.jpg) or vacuum diaphram (located under the battery) could be malfunctioning. The job of these components is to pull on a cable which engages the front, right 4WD hub. I don't think this is likely to be your problem as you should probably hear the encoder motor running (changing the drive mode from 2Hi to 4Hi/4Lo) but there is a sensor on the hub to tell the TCCM when it is engaged, so it could be problem. 3) the encoder motor/module is bad. This is the module/motor that is mounted directly to the transfer case, who's job it is to physically move the gears of the transfer case to put the TC into the various modes (2Hi, 4Hi, 4Lo). You also want to check the wires at the encoder motor as they are exposed to the elements and could be damaged by something flying up under your vehicle (not likely, but possible). 4) The TCCM (located under the passengers kick panel) has wires that are corroded / broken. Poor connections anywhere along the route will cause problems and most times intermittently, which are a real PITA to find. The TCCM could be bad as well. If I had to guess either your encoder motor is shot, or bad wires on the TCCM. My understanding is that if the 4x4 sw


Take your time and start with the simple like always and check your 4WD selection button. Remove the switch panel from the dash, just pops out and test the wire leads to the switch. Did the TCCM Self test performed without any issues as noted. ( TCCM Self-Test: Observe the transfer case shift control switch indicators while turning the ignition switch to RUN. A properly operating system will flash all indicators and then will return to the current gear. If the system is operating normally, then proceed to Displaying Codes. )

it was the transfer case motor bought a new one for $140 and it works now

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