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2004 chevy trailblazer_lt
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Discussion Starter #1
I have an '04 Blazer with the Vortec 4.3 I6. ~73K miles.
Service: Oil changes only.

I've used Auto 4WD several times over the past few months. Every so often, the 4WD light on the dash blinks once for just a split second, then goes away for weeks.

Just recently, with 4 inches of snow on the ground and zero degree temps, I went to place it in AWD again while parked in my driveway letting the truck warm up. The light came on steady this time. No weird sounds or anything and it drove fine down the street in AWD. I went ahead and placed it back into 2 HI just to be safe. After I reached my destination, turned off the truck and came back later to restart, the light had cleared. I haven't tried to place it in AWD again in case there's a real problem!

Any ideas? Should I just take it into the dealership to be serviced?

I can do a lot of stuff mechanically, so if anyone knows whether this is a simple fix, I could probably do it!

Thanks!
 

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2004 gmc
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It's difficult to know that you're REALLY in A4WD mode unless you're on a slippery surface and force some rear wheel spin.

Have you tried, or can you try 4HI and 4LO modes and report that they work or don't work OK?
 

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Just to clarify ... do you have a "Blazer" with the 4.3L V6, or do you have a "Trailblazer" with the 4.2L I-6?

I had a 99 Blazer before and I know mine blinked when switching between settings and I never had any problem with it. I have not used my 4x4 in my TB recently to remember if it blinks or not.

I would try using the 4HI setting to see if you have any problems with that.
 

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2004 chevy trailblazer_lt
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Check out this thread too:
http://forums.trailvoy.com/showthread.php?t=46356

Next time you are in your truck, turn the key to on but don't start the truck. Cycle the switch through all the settings and listen to the sounds from the encoder (inside near your left knee) and the front axle actuator (near the front axle on the right side of the transfer case.) The encoder that makes a slight quick noise going from mode to mode, and the actuator makes a high-pitched whine going from 2wd to Auto 4wd. If the front axle actuator doesn't engage the axle in about 4 to 8 seconds, it sets the service light to on. This may happen even if the actuator is running a bit slow, so it may go to Auto 4wd but it was just a bit slower than it should be, or it may go on if the front axle actuator tries to engage the axle but fails to do so after about 8 seconds and gives up, leaving you in 2wd mode.

Listen for the sound of the actuator and watch your light. In good conditions, the Auto 4wd light goes on in a second or two. I would be willing to bet yours is running slower than normal, and your light takes anywhere from 4 to 8 seconds to light.

Once or twice, especially in very cold weather, is no big deal. If it is happening with more and more frequency, it is time to change the front axle actuator.

If you are really mechanically inclined, I would try taking apart the old one (once you know a new one is easily available locally) and seeing if you can clean up the inside and regrease it lightly. It uses circuit boards and a high torque motor to move an engagement lever in and out, so if the circuit board is gone, it is likely toast but if it is failing slowly, it may be that something is slowing the motor. If the motor is going bad, replace the actuator but maybe it is a buildup of old hardened grease that can be cleaned up. If you are mechanical, it may be worth a try.

The front axle actuator was a common problem on Blazers with Auto 4wd, just like it is on our Trailblazers.
 

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2004 chevy trailblazer_lt
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Discussion Starter #5
Yes 4 HI! and Yes to Trailblazer

Sorry, yes this is the 4.2L!! I was off by a digit.

Also, to add to the discussion, I had this in A4WD and went to back down the driveway (light now on). I could tell all four wheels were grabbing on the ice-covered snow. I back straight out into the street covered with about 4 inches of packed snow. I placed it back into 2 HI (light still on) and tried to drive back up into the driveway. Slipped and slid everywhere. Then I reversed back into the street (light still on) and put it back into A4WD. It gained traction and drove right back up into the driveway. The light was still on until I drove around town, turned the truck off, then turned it back on. The light cleared. I'm afraid to put it back into A4WD in case that's a real problem.

Thanks!
 

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Which light are you referring to being on? The light on my 4x4 selector is always on based off of which selection is made, and blinks a few times when switching. Do you mean your service 4x4 light is on? Or do you mean that the "A4WD" light stays on even when you switch it back in 2HI?
 

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Discussion Starter #7
Yes it's the light in the dash

Yeah, I'm referring to the light in the dash. I understand how the switch light works and this is definitely not a switch problem.

When the weather warms up a few degrees, I'm going to try the relay box idea and see what happens when I cycle through the different ignition positions.
 
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