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2004 chevy trailblazer_ltz
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3 Posts
Discussion Starter · #1 ·
Hey guys. Thanks in advance for helping me.

A few nights ago I was trying to get out of an icy parking lot, was slipping so I switched into 4Hi as it was an ice skating rink. Everything switched over just fine and I went on my way. Back on clean roads I switched back to 2wd and the light blinked as normal in transition, but after about 10-20 seconds of blinking it jumped back to 4Hi and stayed steady. I tried switching to A4wd which worked, but now it's stuck in a4wd- I try to switch it into 2wd, 4hi, even 4lo (in N) and all I get is blinking and then a jump back to steady over a4wd. The service light is not on, and only went on once for a split second and went off when I turned the car off and on again. It is not on now. Disconnected the battery for 10 mins to no avail.
Help!
 

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2003 chevy trailblazer_lt_ext
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967 Posts
Did you try to set it to 2HI when shut off and see what happens? When I was having similar issues a few years ago, that always got me back to 2HI.

I can see one of two things, either the encoder motor is bad (which was my issue a few years ago), or you simply need to change your transfer case fluid. I'll save the rest for Roadie to comment on. He can tell you a whole lot more than I can about this.
 

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2004 chevy trailblazer_ltz
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Discussion Starter · #4 ·
Looks like I'll be replacing the encoder motor. Any tips on how to get the motor in properly as I can't set the switch to 2wd? Lookin over the forum I can see that there are some issues with things aligning properly if you can't get it in 2wd.
 

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2004 gmc
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26,181 Posts
Doc's got it. Tired or congealed grease in the encoder motor, or a transfer case that isn't letting the encoder motor turn its control shaft.

How many miles, and was the transfer case fluid changed every 50K as required? How's your level today?

This also points out to everybody lurking to get to know the NOISES your 4WD system makes. Each of the mode transitions has a distinctive sound or one or two motors doing their things for different lengths of time. You can do it with the engine off, but the ignition set to RUN. Memorizing the noises, and knowing how the two items (front axle actuator and transfer case encoder motor) do their jobs, can make for a much less stressful diagnostic session when something quits working.
 

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2003 gmc envoy_slt
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7,190 Posts
Try as Doc Brown posted:

Put the switch in 2HI and turn off the truck,

Restart and see if the light stays steady in 2HI.
 

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2004 chevy trailblazer_ltz
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Discussion Starter · #7 ·
Tried the 2hi Key trick. No luck. Fluid was just changed 5k mi ago, no leaks. Level is good. Any tips for switching the motor when you can't get the transfer case into 2wd? Sounds like this can be a huge problem when trying to replace the encoder motor.
 

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2004 gmc
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26,181 Posts
You can rotate the shaft after you get the motor off, or better yet, connect the new encoder motor to the wiring, and while it's in the air, put the mode control switch to A4WD to make the motor move to match the TC shaft.

People use that trick all the time to match HVAC actuators to the shafts they're putting them on.
 

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2004 gmc envoy_sle
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I have had this same problem last month. Turn the truck on and put the vehicle in Neutral, than try changing it to another setting. That work for me for now but still could be a problem with it.
 
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