I havetwo problems with the 4wd on my 2004 blazer. It is a 2,4hi, 4lo version, not autotrac.

4wd Engagement:
If I disconnect/reconnect the battery and drive,4hi takestwo button pushes and then engages. It will shift back to 2wheel with a button push or two.It will not go back into 4hi unless I disonnect the battery again and repeat. Runningcodes gives a"motorencoder error".

Noise:
The front differentialhumswhen NOT engaged in 4wd. It goes away completely when itis engaged in 4wd.It sounds very similar to a wheel bearing that is going bad when it occurs.
Is the front diff not fully disengaging?

Should I replace the motor/encoder, vacuum switch, or both. Can one cause and error in the other?

I appreciate any advice, thanks

Duane

 

DTC Displaying
[ol]Turn OFF the ignition for 10seconds.
Connect PIN13 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.
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 3second pause and then repeat.•
If more than one code is stored, the first code will blink, followed by a 3second pause and then the second code will blink.•
This sequence will continue until PIN13 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 Step2. If the circuits are complete, then replace the TCCM

This is just a starting point, when you have a code (1, 2, 3 or 4), let us know and we'll see if we can help[/ol]

 

Chevy Lover,
Thanks for your reply. I double checked the codes todayusing pin 13and am still getting just two blinks, no others. Does replacing the actuator unit fix this? Is it possible that it doesn't retract all the way and cause a slight opening in the vacuum switch?

My priority is to get the 4wd shifting reliably, I can live with a 130$ fix, but also worried about the vibration/noise in the front diff. Again, it's intermittent, so, I don't think it's as serious as a bearing going, but it's starting to drive me crazy. Any thoughts? Thanks

Duane

 

I had a noise after driving for 30 minutes or so on the highway, actually it would start after I slowed down. Turned out my vacuum switch was going bad and the vacuum created while driving was aprtially engaging my front axle. The resolution was to replae the vacuum switch. The noise I had was like a card in the spokes but only louder, faster, and metalic in sound. Not saying its your problem, but it might help you out some.

 

Thanks, I'm leaning toward replacing both the transfer motor and the vacuum switch over the holidays.... While I'm under there and the tools are out.... Another thread also pointed to the vacuum switch with similar intermittent noise as I described too. I'll be sure keep checking back here in the mean time for any other suggestions and also post the results.

 

2 blinks means code 2 which is probably either the encoder motor on the transfer case or a poor electrical connection to the encoder motor.

Hopefully fixing one problem will fix both issues.