Yes, I did the whole Search thing already. Now that that is out of the way, I'm a bit confused on my Blazer's 4x4 issue.

My 99 is an auto with the 4 button 4WD switch on the dash.

The issue is blinking lights on the 4HI and 4WD Auto after switching from 2HI. It goes in/out of 4LO just fine and back to 2HI just fine.

My research lead me to the encoder motor sensor. I just replaced it (and the motor) with a used one and the blinking light issue remains. Only now when I put it in 4LO that light now blinks. Of course the used encoder sensor could be bad as well. That's a given.

I do believe my truck is fully engaging 4x4 whenever it is placed in 4HI and/or 4 Auto. I can hear the TCCM clicking after pressing any of the buttons and can also hear and see the Tach move slightly indicating the vacuum actuator doing it's job.

Now couple of questions.....

1) Does the TCCM need to be reset to clear the codes from the old encoder motor ?

2) How can I determine if my 4x4 is actually engaged fully ? Icy roads would be great for this test! Do I just jack the truck up on jack stands and watch the wheels or what ?

Thank you.

Frustrated in Ohio

 

You could use a land mass and add water . Once vehicle is in combination of said elements accelerate rapidly while turning. Evidence should be in the pudding.

 

Anybody ?

 

Test the 4 wheel drive in some mud.

 

If I can find some I'd love too do that!

 

Anyone out here ?

 

'03 Chevy Blazer -- where's my 4 wheel drive? (UPDATED) | KyleStubbins.com

 

I did double check the TCCM wires and grounding points. All checked out and did not fix the issue.

I then decided to follow other ideas and start checking for a Vacuum leak.

I found a dry rotted hose to the right of the brake booster (driver's side), hose was broke off completely.

Fixed the hose and FIXED my Blazer's blinking lights on the 4x4 switch and now my 4x4 works PERFECT !

 

Not that it matters now, but I had to reset ECM (disconnect battery for 15 minutes) on a 1995 blazer after an encoder motor replacement. The defective one didn't sense 4HI, replacement behaved the same as the defective one shifting to 4LO or 2HI only until the ECM reset. You might be able to return a functional encoder motor.

 

Thanks for the tip. Can't return electrical parts to a Wrecking yard.