98 blazer 4 wheel drive not engaging
 

Hey Ive been trying to solve this 4 wheel drive issue by myself for the past few weeks and haven't had any luck. As of now when ever i press the button to go into 4hi or 4lo the 4 wheel light will blink a few times and it will go right back to 2 wheel drive. You can hear the clicking on the TCCM on the passanger side and there is no other engaging noise in the transfer case and theres no air going threw the vaccum so im assuming its just electrical. I replaced the TCCM, vaccum hose switch on transfer case and the push buttons on dash. I also took apart my encoder motor on the case cleaned it out and seen no problems. also theres a problems with my upper screen where it shows the temperture and compass it flickers on and off randomly and im thinking it could be linked to my 4wheeldrive shorting out maybe? thanks!

I saw you checked the vac lines. Did you check the actuator under the battery tray? I dont know about the elec with your overhead though. I know mine did something. Similar when the vac line going to that actuator rottes out on me.

My actuator works fine, i disconnected the vac line that goes into it and no air goes threw it. Its something wrong in the early stage of the system before the vaccum engages.

I'm assuming you have a 3 button 4wd system. When you push the buttons you should be able to here the encoder motor on the transfer case shifting positions. If you are only hearing the tccm click, the encoder is not operating. Again this is assuming you have a 3 button system.

If the switch on the front axle housing is not tripped when you select 4WD, the TCCM will default back to 2WD.

With the engine at idle: When you select 4WD, the vacuum switch on the transfer case supplies manifold vacuum to the actuator under the battery tray. The actuator pulls a cable that operates a clutch on the right front axle shaft. When the clutch is engaged it trips the switch and 4WD is engaged. When you select 2WD, the vacuum must release the actuator immediately.

I had this exact same problem. reason you are not hearing the encoder motor is b/c you probaby have the car running, it's very hard to hear that little motor engage over the noise coming from the engine.

i can almost guarantee you it's a bad vacume hose.

do this

turn the ignition key to start but dont actually fire up the engine. while sitting in the driver seat open the door and now hit the 4 HI on the dash switch. without the engine noise you should now be able to hear the encoder motor turn and engage. hit 4HI and 2HI a few times. If you hear the motor working but the 4HI is just blinking you probably have a bad vacume hose.

when I had this problem, each component of the 4x4 system worked individually, but when put together i still had no 4x4..........after inspecting all the hoses I found that the vacuum hose going to the air balloon under the battery was broken. replaced it and everything worked fine.

Check the vac line at the fire wall as well

Damn u have a quiet encoder motor then, I can hear mine when i engage it LOL.

I am having a similar problem where the 4wd circuit is shorting and incidentally (like you) the temperature/compass digital readout is not working right. Mine doesn't flicker but rather read "--" for all of the information.

I'm trying to find complete diagrams of the 4wd circuit to see where the Gauges circuit (4) may coincide with the 4wd circuit (15). That would explain the unusual gauge display and the 4wd shorting.

I'll let you know if I find anything that helps. Good luck!

i guess so. i thought mine was dead, i couldnt hear it engage over the engine noise. turns out it was just very quiet. I read on some other forum to try engaging it with the engine off so that way u can hear it better. worked for me. :icon_playing:

I did what you said Tinted and i cant hear a damn thing, i even got someone to hit the buttoms and put my ear right up to the motor. So im pretty sure it could be the encoder motor not working. Ya Mark_D I thought it was a weird coincidence that when my 4 wheel drive started acting up my digital gauges did to. let me know if you find those diagrams

well there you go bud. if the TCCM is clicking but nothing happens at the encoder motor I think you probably should replace it. they are like $120 bux on ebay, or so.

there is a great HOW TO on the zr2usa forum but the forum seems to be down right now. it's fairly easy to do, just remove the front shaft. I heard of some guys having problems getting the shaft off the fly wheel but mine came right out.

1998 NV233 selectable transfer case: If the lights are blinking, it's telling you a code is stored. There are 4 different codes: to retrieve them, ground pin #13 in the data link connector, (bottom connector in the image below):

http://i561.photobucket.com/albums/s...connectors.jpg


Turn the ignition to the run position. Count the blinks and post your results.

I did what you said captain put it in start position and all 3 lights went on for a sec then all of them went out. Then when i went to try it again the lights wouldnt go on. Thanks

With a test light or voltmeter, check both terminals of the following fuses:

In the I/P fuse panel, (left side of dash):
FUSE #15 4WD 10a fuse must show battery voltage with ignition in RUN position.
FUSE #8 CTSY LP 10a fuse must show battery voltage at all times.

In the underhood fuse panel:
ATC FUSE 20a must show battery voltage at all times.
BTSI FUSE 10a must show battery voltage in PARK and NEUTRAL with ignition in RUN position.
CRANK FUSE 10a must show battery voltage in START position.

Post the results of each test.

results with a voltage meter:

4wd fuse= no voltage with the fuse in and i got 14 volts at the terminals
CTSY LP= .009 of a volt with the fuse in and 14 volts at the terminals
ATC= nothing with the fuse in and got .002 of a volt at the terminals
BTSI= .002 of a volt with the fuse in and 14 volts at the terminals
crank fuse i got nothing all around

Just to make sure..... leave the fuse in the fuse panel when testing. Test both terminals on the top of each fuse and make sure the ignition switch is in the positions noted for each fuse in post #15 while testing.

Ya i did exactly what you said and those were the results i got. So im guessing theres something not giving me the voltage i need to my fuses?

Help me out here.... no voltage on either terminal on the top of the fuse? What terminals did you read 14 volts?

ya there was no voltage on the top of the fuse then i took the fuse out and check those 2 points out for voltage and got the 14v. So i ended up checking all the tops of the fuses you listed and took the fuses out and checked the 2 terminal points where the fuses plug into as well.

If you show no voltage on one terminal on the top of the fuse, the fuse is bad, replace it and check it again.

I went out and double checked the fuses tested them with 3 different other fuses that were currently working and im still reading nothing on the voltage meter. Theres gotta be a electrical problem, something shorting out somewhere hence why my overhead led display flickers on and off randomly. thanks alot for the help

try removing/unplugging the over display and try the fuse thing again.

Ok I went out and checked the fuses with the volt meter the correct way and all the fuses are getting voltage where there suppose to be.

Hey, I had a similar problem with my 4wd/gauges and it turned out to be the Front Axle Engagement Switch. Messed up a bunch of the gauges including the data that shows on the overhead LED screen.

For me, the Front Axle Engagement Switch was the problem. Not the 3-prong air connector but the 2-prong electrical connector on the front axle. $8-$13 fix.

Check out my thread here:
https://blazerforum.com/forum/2nd-ge...e-65704/page2/

I had the same problem i just disconected the bat and hook it back up and its ben working for months hope it helps

The flickering also makes it sound like it could be a faulty ground. Check the thread below (and links within the thread) for images showing where the 3 grounds behind the dash are. Make sure they are all tight. If the ground is loose, it could cause the circuits to intermittently drop and regain power.

I know this thread is old, but I'm having the same issues. I've noticed the vent tube for trans leaks air when I manually push in on the actuator. I bypassed the vacuum relay system by putting zip ties around the actuator so the front diff locks in. I go into the truck and all I hear is the tccm click and the 4hi lights or 4 low flash. I moved the truck around and now the lights no longer flash the tccm just clicks when I push the 4hi or 4 low It's still not engaging into 4wd. I've checked the tccm connections, they are good. I've put two different encoder or tfc motors on the truck. They both spin (operate) when they aren't hooked up to the transfer case. I'm going to attempt to ground out the number 9 pin on obd2 connector and see what it flashes. If anything. All else fails I'll manually put it in 4wd to get around in the snow.

any chance it could be related to a ignition switch issue? i have a '97, 3-button. it has a starting problem where you have to hold the key to th start postion as it starts or it wont run, i noticed the other day when i did get it to run that the 4-hi button would blink if i tried to engauge the 4wd. the next day the 4wd worked. i know its not a front axle issue as ive rigged the front axle to always be engaged, its been that way for years (as is my '96). so im wondering if my ignition switch is causing multiple issues.