4x4 Help?

I Have a 2004 Chevy Trailblazer with a Shifting in & Out Of 4wd Problem, Right now it's stuck in 4lo, and I've Replaced the switch, the TCCM, and the Transfer Case Shift Motor with No Luck, the lights on the switch don't blink when I Try to Shift in 2hi, I Think that it's either a fuse or a ground issue, but I Don't know what fuse to check, is there more than 1 (it says Fuse #8 in the underhood fuse box but that Fuse is good), and It Has ground at the motor on the Transfer case, Plus when I try to shift out of 4lo, there is NO Noise from either actuator, Then I saw I could take the shift motor Off The Transfer Case and shift it Manually, with a good pair of channel lock pliers, it moves just a little counter clock wise, and when I put the truck in drive it goes about 10 ft and the Transfer case moves into Neutral, so I put the motor back on (had to twist it a little) oand now it's still Stuck in 4lo, and my "Service 4wd Light" is on!!!! The Only Scan Tool I Have is the Launch Creader Pro CP CRP123, which it doesn't show any Codes for 4wd! Someone Please Help!! This Trailblazer is My Daily Driver and I Can't go over 25mph without The Motor Taching 3000 Rpms which uses up the gas like crazy, Plus I don't want to Ruin anything, even Though I also Have a 2005 Trailblazer 4wd, which worked perfectly, (That's where I got the parts I replaced in my 2004 Trailblazer) The Transmission in my 2005 Bit the Dust, So I Bought this 2004, for 1/8 of what it would of cost me for a tranny and have it installed ( especially Being on a Fixed Income)!!! So Please Can Someone give me a direction on what to check next??? I'd Greatly Appreciate it!!!
 
I guess every one is out 4wheelin in the new snow... :smile: did it ever work? how did you get to this state of "disrepair"... history? You can find the link to schematics here on the site or in one of the regular poster's signature (mooseman).
 

Mooseman

Master Blaster
Moderator
If you can't turn the shaft more than that by hand, it sounds to me like an issue with the transfer case itself and the position sensor in the encoder motor is reporting that to the TCCM, throwing an error.

What was the maintenance like? Was the fluid changed as per the 50k miles interval? It is recommended to do this whether the 4x4 is used a lot or not. There have been failures from neglected fluid.
 
Then I saw I could take the shift motor Off The Transfer Case and shift it Manually, with a good pair of channel lock pliers, it moves just a little counter clock wise, and when I put the truck in drive it goes about 10 ft and the Transfer case moves into Neutral, so I put the motor back on (had to twist it a little) oand now it's still Stuck in 4lo


OK, when the transfer case is in 4Lo the transfer case shaft should be pretty much all the way couterclockwise already. Turning CLOCKWISE from that position will take you next to Neutral and after that to 2Hi. It will NOT stay in this or any other position reliably without being secured by the shift motor or some other means. To place the shift motor in the corresponding position it is recommended to use a pair of 9 volt batteries to both release the motor brake and run the motor to the desired position. This requires a working knowledge of using jumper wires to connect to the proper circuitry at the motor harness. Some have suggested simply connecting the motor harness with the motor NOT attached to the transfer case and then selecting the 2Hi position amd allow the truck to position the motor. This assumes the electronics of the motor are working as designed. Either way, once you get the shift motor in the right place (2Hi) you then reinstall the motor. If I were having issues and had to use the vehicle I would do all this but then pull the ATC fuse so the system won't move the shift motor away from the 2Hi position.
 
Replaced the switch, the TCCM, and the Transfer Case Shift Motor

You replaced with NEW parts or used? Edit: reread your post and see these were used parts.


Right now it's stuck in 4lo

This means the shift indicator light at 4Lo is on steady? And the switch is where?


lights on the switch don't blink when I Try to Shift in 2hi

If the service 4wd light is on this may be normal. With some system faults the TCCM disables shifting. To reset remove the ATC fuse for a short while, maybe a minute or so then reinstall. If the service 4wd light comes right back then you have a current fault. If the system tries to work for a while you likely have an intermittent fault. I used my truck for several years like this with an intermittent fault. It wasn't so difficult for me though as I can reset my TCCM with an app on my phone so when it balked or set a code I didn't have to pull a fuse or even get out of the vehicle to reset it and get back on the road.
 

TB's Trailblazer

Newbie
Thread Starter
I guess every one is out 4wheelin in the new snow... :smile: did it ever work? how did you get to this state of "disrepair"... history? You can find the link to schematics here on the site or in one of the regular poster's signature (mooseman).
Lol Yes 4wd fun in the snow, It worked perfectly when I first bought the 2004, (beginning of Jan. 2021) I Don't know any of the Trucks Maintenance History, But the oil was fine, tranny fluid was fine, runs like a clock, the only thing it needed was rear upper trailing arms ,which I put new ones on approx 2 days after buying the truck, My Dooryard has a slight Incline, so As I was approaching My Dooryard (at Approx. 10 mph), I would switch it from 2wd to 4hi, to beable to make it up the driveway, (until the plow guy plows it) and I would back into my garage, Leave it in 4hi, until I had to go somewhere and would shift it back into 2wd before pulling out of the Garage, until 1 day coming back from a Doctor's Appt. I went To shift it into 4hi, and it took a few but shifted, then it wouldn't shift back into 2wd, so I played with the switch, and it went to 4lo, and has been stuck there since, and that was approx 2 wks ago, and even after replacing all that I mentioned above, (it still doesn't work, the Trailblazer had 198,980 miles when I bought it, now has 199,059 on it, I put roughly about 40 miles a month on it,!!!
 

TB's Trailblazer

Newbie
Thread Starter
You replaced with NEW parts or used? Edit: reread your post and see these were used parts.




This means the shift indicator light at 4Lo is on steady? And the switch is where?




If the service 4wd light is on this may be normal. With some system faults the TCCM disables shifting. To reset remove the ATC fuse for a short while, maybe a minute or so then reinstall. If the service 4wd light comes right back then you have a current fault. If the system tries to work for a while you likely have an intermittent fault. I used my truck for several years like this with an intermittent fault. It wasn't so difficult for me though as I can reset my TCCM with an app on my phone so when it balked or set a code I didn't have to pull a fuse or even get out of the vehicle to reset it and get back on the road.
yes they were used parts from my 2005 Trailblazer, (which worked perfectly before I parked it 3wks ago due to tranny going, that's why I bought the 2004 Trailblazer, figured I could use a lot of the parts off my 2005, seeing so I bought all new brakes & rotors, sway bar end links, muffler, tires, last summer for my 2005!! Yes The Indicator light is on Steady on 4lo, and it stays there No Matter where I try to switch it to, so I just leave the switch on 4lo also!! I've Done that, Removing the ATC Fuse a Few Times, The lights blink when I try shifting and it worked twice before I Changed the TCCM, Then it stopped working ,That's why I replaced the TCCM, with the one in my 2005, I first replaced the Switch itself, cause I was Told that was the Prob, then when that didn't work, I tried the resetting The TCCM, (by Pulling Fuse #8 (in underhood fuse box)), it worked 2 times and then didn't, So I Replaced the TCCM, and that didn't work, so when the Transfer Case Actuator Motor wouldn't make any Noise, I thought it might've been That, because I used my Multimeter to check for power & grounds, which it had, so I replaced the actuator motor and it still didn't work or make any noise, so that's where I got Stuck..
 

TB's Trailblazer

Newbie
Thread Starter
If you can't turn the shaft more than that by hand, it sounds to me like an issue with the transfer case itself and the position sensor in the encoder motor is reporting that to the TCCM, throwing an error.

What was the maintenance like? Was the fluid changed as per the 50k miles interval? It is recommended to do this whether the 4x4 is used a lot or not. There have been failures from neglected fluid.
I Really Don't know what the Maintenance Schedule on it was Like, I Know it had regular oil changes, and all the fluids I could check before I Bought it were in Great condition, Oil, brake, Tranny, power steering,, But the Truck runs Fine, and shifted fine in & out of 4wd, then all of a sudden, it just crapped the bed, Thank-God, it didn't cost a penny to replace the 4wd switch, TCCM, Encoder Motor!!!! But Like I asked about any other fuses, (Besides the ATC Fuse #8 in the Underhood Fuse Box) That would power any of the TC Components, because like I said, (The Motor/ actuator, Encoder, whatever People wanna call it!) Doesn't make any Noise Now when it did when it worked fine!!
 

Mattwurst79

Registered Member
To summarize this:

You have both Voltage and good grounds at both electrical actuators!?
So changing the fwd disconnect motor was an idea although it is strange you don't hear any of the motors.
Im not sure but since you have electrical power at both connectors at the actuators couldn't it be both actuators being bad!?
I mean believing the front actuator will only start when the transfercase motor has turned into 4wd mode!?
I would quit searching for electrical/blown fuse-issues when you have power down there and focus on the actuators. As far as I know the position sensors are integrated in the motors and might be reading false or toast.

Chris
 
So I'm still not clear on the behaviours of the service 4wd light in your truck.... But I have a longshot idea for you to try to get you out of 4Lo. It will sound a little screwy but what have you got to lose?

Setting out some points first. You are stuck in 4Lo. Shifts into or out of 4Lo require the trans to be in neutral. Owners manual states best practice is to have the truck moving slowly, less than 2 mph for this shift. This is to release any built up stress on the current gearing and also allow the intended gearing to get properly aligned for the shift. The procedure I am about to outline will not have the truck rolling but you will need to physically rock the vehicle forward or back a little. Some will say the engine needs to be running for these shifts also. I cannot say this is required as for MY truck, it is NOT required. I can shift into and out of 4Lo with the key ON and engine OFF.

So here goes...

1) select a smooth level surface where you will be able to leave the truck in neutral without the parking brake applied and it can be rocked a couple inches forward and or backwards. If you need to you could place some blocks at one or more wheels to prevent it from going further than a few inches either direction.
2) get in the truck, turn the key to RUN but DO NOT start it.
3) Roll down the drivers window.
4) Press the brake pedal and shift the transmission to neutral.
5) Slowly release the brakes making sure you are not rolling away.
6) Turn the key back towards the OFF position. It won't turn all the way because you are in neutral so just turn it as far as it otherwise will go. Some gauges etc should go off, some will stay on.
7) Pop the hood, get out and remove the 25 amp #8 fuse. Leave the hood open and the fuse readily available.
8) Back in the truck, turn the 4wd selector switch to 2Hi. The key remains where it is do not turn it yet.
8)At the fuseblock replace the 25 amp #8 fuse.
9) Now, with the drivers door closed, place yourself where you can get the truck rocking a little forward and back, forward and back, and while it is moving this way turn the key to RUN. At this point the TCCM should initialize, see the request for a shift to 2Hi, the trans is already in neutral so the shift should be attempted and you at the least should hear that.


I did this 3 times just now with my 2002 Trailblazer. When I had the truck moving a little the shifts happened as desired. The one time I did NOT rock the vehicle I heard the shift attempt but it failed and the light went back to solid at 4Lo with the switch at 2Hi. Also the front disconnect went from engaged at first to disengaged while the shift was attempted, then back to engaged when the shift failed and the system returned to 4Lo.
 

TB's Trailblazer

Newbie
Thread Starter
So I'm still not clear on the behaviours of the service 4wd light in your truck.... But I have a longshot idea for you to try to get you out of 4Lo. It will sound a little screwy but what have you got to lose?

Setting out some points first. You are stuck in 4Lo. Shifts into or out of 4Lo require the trans to be in neutral. Owners manual states best practice is to have the truck moving slowly, less than 2 mph for this shift. This is to release any built up stress on the current gearing and also allow the intended gearing to get properly aligned for the shift. The procedure I am about to outline will not have the truck rolling but you will need to physically rock the vehicle forward or back a little. Some will say the engine needs to be running for these shifts also. I cannot say this is required as for MY truck, it is NOT required. I can shift into and out of 4Lo with the key ON and engine OFF.

So here goes...

1) select a smooth level surface where you will be able to leave the truck in neutral without the parking brake applied and it can be rocked a couple inches forward and or backwards. If you need to you could place some blocks at one or more wheels to prevent it from going further than a few inches either direction.
2) get in the truck, turn the key to RUN but DO NOT start it.
3) Roll down the drivers window.
4) Press the brake pedal and shift the transmission to neutral.
5) Slowly release the brakes making sure you are not rolling away.
6) Turn the key back towards the OFF position. It won't turn all the way because you are in neutral so just turn it as far as it otherwise will go. Some gauges etc should go off, some will stay on.
7) Pop the hood, get out and remove the 25 amp #8 fuse. Leave the hood open and the fuse readily available.
8) Back in the truck, turn the 4wd selector switch to 2Hi. The key remains where it is do not turn it yet.
8)At the fuseblock replace the 25 amp #8 fuse.
9) Now, with the drivers door closed, place yourself where you can get the truck rocking a little forward and back, forward and back, and while it is moving this way turn the key to RUN. At this point the TCCM should initialize, see the request for a shift to 2Hi, the trans is already in neutral so the shift should be attempted and you at the least should hear that.


I did this 3 times just now with my 2002 Trailblazer. When I had the truck moving a little the shifts happened as desired. The one time I did NOT rock the vehicle I heard the shift attempt but it failed and the light went back to solid at 4Lo with the switch at 2Hi. Also the front disconnect went from engaged at first to disengaged while the shift was attempted, then back to engaged when the shift failed and the system returned to 4Lo.
Thanks Bud I'll Try That!!!!
 

TB's Trailblazer

Newbie
Thread Starter
To summarize this:

You have both Voltage and good grounds at both electrical actuators!?
So changing the fwd disconnect motor was an idea although it is strange you don't hear any of the motors.
Im not sure but since you have electrical power at both connectors at the actuators couldn't it be both actuators being bad!?
I mean believing the front actuator will only start when the transfercase motor has turned into 4wd mode!?
I would quit searching for electrical/blown fuse-issues when you have power down there and focus on the actuators. As far as I know the position sensors are integrated in the motors and might be reading false or toast.

Chris
Thanks!!!!
 

Mektek

Hobbyist
Ordinarily the shift to 4lo is limited to parameters set by the TCCM. But if there is a problem then some of this goes out the window. I had a shift to 4lo happen at 30 mph - that's quite a shock but does not appear to have done any damage.
Others have had it happen at highway speeds which does a lot of damage to the driveline.
If the OP had old used parts there could be a problem with them too.
Check the impedance of the transfer case encoder ring on the motor harness to be sure it has continuity. Even if it does, an old used one can be flaky while still having correct impedance. The encoder ring giving correct readings is absolutely critical to the shifting working correctly.
 

TB's Trailblazer

Newbie
Thread Starter
I Want to Thank-You ALL Very Much, For the Feed Back/Replies to my Question Above, I Finally Fixed my Problem, by using a simple multimeter on a few fuses in the underhood fuse block, I found both my Horn Fuse (fuse # 21) Blown and Also a Truck Body Controller Fuse (Fuse # 31) Blown, Replaced Both Fuses, and Now Both the Horn works and shifting through the 4wd ranges work Great!! So Now I have a Spare actuator switch, TCCM, and TC Actuator Motor :smile: Again Thank-You All So Very Much for the Help & Suggestions!!!
Tim
 

jmabs509

Newbie
I Want to Thank-You ALL Very Much, For the Feed Back/Replies to my Question Above, I Finally Fixed my Problem, by using a simple multimeter on a few fuses in the underhood fuse block, I found both my Horn Fuse (fuse # 21) Blown and Also a Truck Body Controller Fuse (Fuse # 31) Blown, Replaced Both Fuses, and Now Both the Horn works and shifting through the 4wd ranges work Great!! So Now I have a Spare actuator switch, TCCM, and TC Actuator Motor :smile: Again Thank-You All So Very Much for the Help & Suggestions!!!
Tim
Wow glad you got it fixed, but how is this related? Horn fuse has nothing to do with the 4x4 i would think? What is the truck body controller fuse do? I am chasing 4x4 fix also on my 04 TB I6
 

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