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2004 chevy trailblazer_ls
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Discussion Starter #1
Basically whats happening is it won't shift in to any of the four wheel drive selections. you can hear the motors trying to engage the lights all blink and then it goes back to 2wd. Took it to a trusted mechanic and he says its gonna be about a thousand dollars becasue mine has all wheel drive its not that easy to fix and something has to be programmed. Mine is a 2004 chevy trailblazer 4.2L V6. dont wanna dump a thousand dollars into this thing. sounds like i need a encoder motor which i have found this part online for 200 dollars.
 

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If the lights blink, then go back to 2HI, you don't have a bad TCCM (control module) which is the only thing that needs a dealer to reprogram.

You have either a bad front axle actuator or encoder motor or transfer case. The first two have sensors that report back to the TCCM whether or not they succeed in changing state when commanded to. The blinking is a sign that they have failed.

The encoder motor turns a shaft on the transfer case, and if that's jammed or gummed up, it can fail the sensor feedback test as well, but it might not be the encoder motor's fault.

You need a competent mechanic who knows the trailblazer system, and isn't guessing and telling you fibs like it's an "AWD" system when it is not. It's a TRUE 4WD system that happens to have an "A4WD" mode on the selector switch. An important difference.

How many miles do you have, and was the transfer case fluid changed religiously every 50K as required by the manual? It's a very, very important maintenance item on these systems.

You also have an I6, not a V6 engine. :confused:
 

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Discussion Starter #4
It has 87,000 miles and no the transfer case fluid hasn't been changed. bought it with 49,000. Should I try that first and see what happens. I hardly ever use the four wheel drive and was told that I need to use it to keep things running correctly. Thanks roadie I appreciate you help and sorry for calling it a v6 when yes its a inline 6.:weird::weird:
 

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2002 chevy trailblazer_ls
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Took it to a trusted mechanic and he says its gonna be about a thousand dollars becasue mine has all wheel drive its not that easy to fix and something has to be programmed.
So much for being a trusted mechanic... I mean, maybe he knows how to fix stuff and do it right, but he definitely doesn't have a clue on the Trailblazer 4x4 system. Go to someone else...
 

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2004 chevy trailblazer_ls
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Discussion Starter #6
I guess I will start by going and getting my fluids changed. If that don't work i'll try the encoder motor.
 

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A fluid transfer pump helps out greatly doing the transfer case. Also, make sure you ONLY use the GM AutoTrak II fluid in the transfer case (2 bottles). And another thing - remove the fill plug FIRST - Last thing you want to do is pull the drain plug and drain the case, just to find the fill plug is stuck and you can't get it off! Both use a 10mm hex key - I had to use a pipe on the end of my hex to get enough leverage to break the fill plug free.
 

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2004 chevy trailblazer_ls
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Discussion Starter #9
Alright guys I just picked up my tb from the mechanic he claims its the computer box underneath the dash in front of the driver side door that needs to be programmed. I took it to a new mechanic to get another opinion. Im hoping for a cheaper alternative on this opinion. any thoughts?
 

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id say listen to the guy who knows what he is talking about. dealers will try to throw fancy crap at you to get money outta you. expecially if your not very well versed on the problem. id look into the encoder motor and sensors before paying some dealer to reprogram. worst case. you have new parts that will last.:thumbsup:
 

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Again it doesn't sound like anything that needs a reprogramming to be fixed, Like it has been said before you should try the actuator or encoder motor first just my opinion though. I had this same problem on my on myy TB when I purchased it, I was able to get it for alot less this way and I know it was likely one of three things I replaced the both and didn't need to have anything reprogrammed this doesn't mean that you 100% won't need anything reprogrammed just that you should try the others first.
 

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It may be cheaper to try the dealer TCCM reprogramming than to slap in a new actuator or encoder motor. But personally I think your mechanic isn't absolutely certain how our system works and he's guessing. It could be a bad TCCM in that case, and you'll have wasted your money at the dealer.

Too bad you don't have a local trailvoy buddy to trade parts with for the diagnostic work.
 

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hi all my new freind

i am not to good in english so be patien with me i got 2003 trail blazer and the tight on the knob ho is write 2wd 4wd lwd or hwd i have no light any wher and no 4wd somebody could help me please
 

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Is the "Service 4WD" light on your dashboard illuminated?

If yes, you may have a bad TCCM. (transfer case control module).

Are you going to fix it yourself or pay a trained mechanic?
 

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2002 gmc envoy_slt
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my 4x4 issue

I have a 2002 envoy and my serive 4wheel drive light just came on,... non of the lights on the switch selector will change out of 2hi and my back hatch is now locked and wont lock on to close. I recently took my suv to midas and they said that the diff's are fine. I dont know what to do,.. someone plz help It has 150,000 miles ...this is my first suv.
 

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kstartheking: Welcome.

The back hatch issue is probably in the latch mechanism. Nothing to do with 4WD.

When you took it to Midas, did you tell them to change the differential fluid? They can't POSSIBLY tell you your diffs are fine without changing the fluid. They can just tell you the level is OK. That service was due at 100K miles.

Do you know the maintenance history? How long in time and miles have you owned it?

Did you or Midas look at the transfer case? Its fluid needs to be changed every 50K miles or else you might have exactly your problem. If the fluid's NEVER been changed or looked at, the transfer case might be toast.

Can you describe exactly what happens when you turn the mode switch from 2HI to A4WD? Describe any flashing of the switch lights and noises under the vehicle.

2002 vehicles were notorious for bad TCCMs (transfer case control modules). The question I asked the previous poster also applies to your situation. Are you a moderate DIY mechanic who wants to learn the systems and fix it yourself, or are you looking for confirmation that you are hosed and need to locate a trustworhy mechanic who knows the trailvoy systems and can fix it competently? Can you afford a dealer visit if you have no good independent mechanics to choose from?
 

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Bill - we should all take up a collection for you to do a "How to identify and fix your TrailVoy 4x4 System" video series
:undecided

... get you some junkyard spares to play with and rip apart
:yes:
 

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If the lights blink, then go back to 2HI, you don't have a bad TCCM (control module) which is the only thing that needs a dealer to reprogram.

You have either a bad front axle actuator or encoder motor or transfer case. The first two have sensors that report back to the TCCM whether or not they succeed in changing state when commanded to. The blinking is a sign that they have failed.

The encoder motor turns a shaft on the transfer case, and if that's jammed or gummed up, it can fail the sensor feedback test as well, but it might not be the encoder motor's fault.

You need a competent mechanic who knows the trailblazer system, and isn't guessing and telling you fibs like it's an "AWD" system when it is not. It's a TRUE 4WD system that happens to have an "A4WD" mode on the selector switch. An important difference.

How many miles do you have, and was the transfer case fluid changed religiously every 50K as required by the manual? It's a very, very important maintenance item on these systems.

You also have an I6, not a V6 engine. :confused:
If the lights blink, then go back to 2HI, you don't have a bad TCCM (control module) which is the only thing that needs a dealer to reprogram.

You have either a bad front axle actuator or encoder motor or transfer case. The first two have sensors that report back to the TCCM whether or not they succeed in changing state when commanded to. The blinking is a sign that they have failed.

The encoder motor turns a shaft on the transfer case, and if that's jammed or gummed up, it can fail the sensor feedback test as well, but it might not be the encoder motor's fault.

You need a competent mechanic who knows the trailblazer system, and isn't guessing and telling you fibs like it's an "AWD" system when it is not. It's a TRUE 4WD system that happens to have an "A4WD" mode on the selector switch. An important difference.

How many miles do you have, and was the transfer case fluid changed religiously every 50K as required by the manual? It's a very, very important maintenance item on these systems.

You also have an I6, not a V6 engine. :confused:
Hey, seems like this is the place to go. Been reading posts and can't seem to find my answer.
I have a 2002 TB, 270000 km but I just purchased.
I'm having an issue getting it to engage in 4-wheel drive. I have no warning lights on the dash, and the switch illuminates properly. I can run the switch through all the spots and everything illuminates as it should. When I go to all-wheel drive the light illuminates, when I go to 4WD light illuminates, and when I go into 4 Low the light illuminates and you assume that everything is working properly. But it doesn't actually engage in 4-wheel drive, and I don't hear anything happening underneath. Just wondering if it's an encoder motor or if it's the transfer case motor that I need to change. Fluid change and everything else is up to date
 

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First off...the terminology matters...your 2002 TB does not have an "all wheel drive" mode. It has an "A4WD" which is automatic 4 wheel drive. NOT the same as AWD and not all wheel drive. What we have (A4WD) puts the system in a ready state for 4 wheel drive where a very small amount of torque is available to the front and the vehicle monitors the front vs rear wheel speeds. When the vehicle computers detect that the rear wheel(s) are spinning faster than the front(s) it engages a clutch in the transfer case to give more power to the front wheels. When the fronts then turn the same as the rear the clutch is reset back to the the " ready" position. Most people recommend not using this mode at all as it has a habit of engaging harshly. Some call it the "slip bang" mode!

Anyway,,, that aside, you can do a quick test by shifting the vehicle into 4Hi, turn it off, jack up ONE front wheel (NOT any more than the one) and see if you can turn this wheel around. If it turns you are no doubt NOT in 4WD.

When I first got my 2002 TrailBlazer it acted like yours, except that I DID hear the shift motors. But I had no 4WD at all. In my case I found that my front axle disconnect had failed internally. The actuator for this front axle disconnect was operating as it should but internally was unable to engage and lock the front axles together as it should.
 
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