4wd 4x4 lo button flashing

The service 4wd light comes on from time to time.

I've been having trouble with the 4hi and Auto 4wd button responding. Most times, nothing happens - 2hi just stays lit.

Now, I've noticed a couple times after I start up, the 4lo button flashes for 30 seconds, or so.

Any ideas?

I checked the actuator under the battery and things look fine.

What year?

I've got a similiar problem.
I have a 2000 4.3 blazer.
Driving in 2HI, engage Auto 4wd then the 4LO light blinks for 30 seconds or so.
Put the car in neutral and select 2HI, 2HI blinks then I can hear it engage into 2HI from 4LO.

Thank you for your help.

My bad.... My jimmy is a 2001.

Do you have the same tires on all four corners?

BlazerLT,

Yes. Same tires on all four corners, P235/75R15.

My 4x4 will not switch to 4LO unless I switch to Park, then back to drive.

yes you have to be in neutral to engage 4lo - but you sound like you are having other issues - the module itself under the switch could be bad , you could try resetting the computer , others have had to do this with this year .

Yes, same tires on all corners.
and yep, already reset the computer.

You have 4 button so check the vac solenoid on the firewall and see if it works - push 4Hi button and see if you hear the front actuator engage the pass side CV axle. Then search all the posts on the fixes - all posted many times.

The service 4wd light comes on from time to time.

I've been having trouble with the 4hi and Auto 4wd button responding. Most times, nothing happens - 2hi just stays lit.

Now, I've noticed a couple times after I start up, the 4lo button flashes for 30 seconds, or so.

Any ideas?

I checked the actuator under the battery and things look fine.

Scanner time on that one:rofl: :lol2: .

You need to get out a engine and transmission capable scanner and check for transfer case codes.
If you can get any codes post back code no.

usually when your service light latches it indicates a fault in the encoder motor circuit. ie to ground or open. I would scan for transfer codes and check back.

1st Check vac actuator under battery tray for tears, or leaks, and that the vac hose is connected. Replace if found

2nd Check vac hose leading from vac actuator to vac switch on transfer case for cracks and dry rot. Replace if found.

3rd Check remaining 2 hoses from vac switch on transfer case for dryrot or cracks Replace if found.

4th Check for the presence of tranny fluid in the vac hoses (this is fairly common)

If all of the above are fine, disconnect your negative battery cable for 1/2 hour then reconnect it. If your 4x4 works after that you probably have a failing TCCM (Transfer case control module)

If that doesn't solve it, it's most likely the encoder motor

Sorry for the untimely response but after following the advice of rlilth, there was a hole in the hose coming from the vacuum actuator.

Now I have an extra 4 button 4WD switch that works fine.

If anyone wants it, let me know. I would be willing give it up for $15 plus S&H.

BTW, the below link was also helpful:
www.automotiveforums.com/vbulletin/showthread.php?t=340818

Thanks for all your help.