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2005 chevy trailblazer_ls
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Discussion Starter · #1 ·
Last year when it got cold my 05 Traillazer LS started having issues. When it got cold and snowy, the 4wd switch lights would all flash when the car was started and then go to the 2hi or whatever was selected and that light would flash then after 15-20 flashes all lights go out and have no ability to use the 4wd. The weather broke in 2 days and all was good until it got cold and snowy this month and it started again. I finally broke down and took to dealer. Was diagnosed as the actuator on the front axle.......replaced. this did not fix it. They replaced a spider gear in the front axle area that the actuator engages, and thought was fixed. But was inside the warm shop. They parked it outside overnight and you guessed it, same issue. Took it back inside and can't find what is problem. Said they checked the TCCM (?) but it was not that. I feel this is electrical issue as the trans/4wd works great in warm times......ANY IDEAS FOR ME TO RUN BY THE DEALER? They have had it for a week so far. I feel they are making honest effort but its a mystery...
 

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2004 gmc
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It should be obvious to a trained and experienced mechanic, but they need to drag their Tech II tool out to the truck while it's cold and misbehaving. If it isn't the TCCM (transfer case control module) which is behind the dash near the driver's left knee, then it's the wiring or the switch. The Tech II tool can command the TCCM to exercise the front axle actuator PLUS the encoder motor that changes the modes on the transfer case itself.

If the Service 4WD light never comes on, then that rules out a communication issue from the PCM to the TCCM.

Are you paying them to go through this guessing game, or do you have an extended warranty? They should have access to better tech support engineers at GM than we are at trailvoy, you'd think.
 

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2005 chevy trailblazer_ls
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Discussion Starter · #3 · (Edited)
Paid 500 bucks for initial repair, that didnt do it. They havent said anything yet. Gave me a loaner 03 TB til they figure it out. Never a service 4wd light
 

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2005 chevy trailblazer_ls
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Discussion Starter · #4 ·
The dealer finally listened a bit to me. They let it sit outside and checked the TB after sitting in cold, voila, encoder motor sensor bad. Works great now............. SO Far...... no extra charge for troubleshooting a whole week but still got 475 bucks but I got my car back.....I'll take it!
 

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2004 chevy trailblazer_ls_ext
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Free fix

FREE FIX. Hi. I have the same issue with my 2004 Trailblazer. In the cold, sometimes the 4wd selector switch lights flash at start up, and after 10-15 seconds, they go off. After thinking about it, I wondered if the Encoder motor was having a syncing/positioning problem. The next time I started it up, when the selector lights began to flash, I quickly pushed the brake pedal and shifted the gear lever to Neutral. BINGO, it worked!!! The selector light locked solid and functioned normally. I live in a snowy climate, so yes, the transfer case is shifting into AWD and 4HI after doing this.
 

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2004 isuzu ascender
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thank you!

I had same problem with my 04 isuzu ascender( identical to 04 tb) I read your post about shifting into neuteral, and, like you explained, it resolved instantly! thank yiu so much for saving me what was sure to be big bucks at the stealership!!
 

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2004 gmc envoy_slt
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Not to burst anyone's bubble, but this may be a temporary solution. It sounds to me that something is binding either in the transfer case or the splined disconnect causing the encoder motor or the actuator not to complete its action. Selecting neutral eases some tension and allows the action to complete. Normally, going into or coming out of 4HI or A4WD can be done in gear and moving. Eventually this problem may become worse.
 

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2004 chevy trailblazer_ls_ext
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EnvoyBoy2004,

Thank you for your reply, but This problem occurs when the temp dips below 10-20 degrees F. Sometimes as little as a 5 to 10 degree dip will render the 4wd inoperable. Also, why would the gears bind with this temp change? Also, what is the tension difference from when the TB is in neutral compared to Park? I have an electronics background. When the temp goes down, resistance goes up. There is a reason the problem is resolved when the actuator motor sensor is changed (electronic). I understand and respect your concern. This is not a fix for all 4wd problems, but it seems to work in this situation. I will save the $500.
 

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2007 chevy trailblazer_lt
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FREE FIX. Hi. I have the same issue with my 2004 Trailblazer. In the cold, sometimes the 4wd selector switch lights flash at start up, and after 10-15 seconds, they go off. After thinking about it, I wondered if the Encoder motor was having a syncing/positioning problem. The next time I started it up, when the selector lights began to flash, I quickly pushed the brake pedal and shifted the gear lever to Neutral. BINGO, it worked!!! The selector light locked solid and functioned normally. I live in a snowy climate, so yes, the transfer case is shifting into AWD and 4HI after doing this.
And this is why I love forums! i just bought an 07 trailblazer and literally the next day had this problem. Thanks for the free fix, worked like a charm :thumbsup:
 

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Free fix

FREE FIX. Hi. I have the same issue with my 2004 Trailblazer. In the cold, sometimes the 4wd selector switch lights flash at start up, and after 10-15 seconds, they go off. After thinking about it, I wondered if the Encoder motor was having a syncing/positioning problem. The next time I started it up, when the selector lights began to flash, I quickly pushed the brake pedal and shifted the gear lever to Neutral. BINGO, it worked!!! The selector light locked solid and functioned normally. I live in a snowy climate, so yes, the transfer case is shifting into AWD and 4HI after doing this.
This worked for my 06 Envoy xl Denali
 

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Free fix

FREE FIX. Hi. I have the same issue with my 2004 Trailblazer. In the cold, sometimes the 4wd selector switch lights flash at start up, and after 10-15 seconds, they go off. After thinking about it, I wondered if the Encoder motor was having a syncing/positioning problem. The next time I started it up, when the selector lights began to flash, I quickly pushed the brake pedal and shifted the gear lever to Neutral. BINGO, it worked!!! The selector light locked solid and functioned normally. I live in a snowy climate, so yes, the transfer case is shifting into AWD and 4HI after doing this.
Thank You for the heads up and your knowledge. This FREE FIX worked perfectly ! ! !
 

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Hi, this is as close as I can get to a forum for my problem.

Recently - along with several other problems, my 4wd selector switch and possible the entire transfer case system, went sideways. The first was the little dash light top right that shows a 4wd issue came on. It is intermittent. O'Reilly's scanner detected no codes. (Not shocked.) The next indication (not at the same time) was when starting up, as usual, the 4 LEDs flash and normally goes to 2WD. It instead showed 4wd low. I tried moving the selector back and both to different positions - the selection will flash (i.e. auto) but then never light up and it stays at 4wd low. Sometimes when starting all the lights flash then all go out and I get nothing. It appears to drive normally most of the time. Sometimes it does drive like it is 4wd hi.

Along the way the selector knob on the switch broke off so it now has a new switch thanks to NAPA. Not expecting it to solve the problem - it did not, but at least I can now try switching again.

I tried the trick of pulling fuse 8. No luck
I tried the trick of after starting, shifting to neutral. No luck.

Recommendations on what I should go after next?? TCCM?? Actuator on transfer case? Working on a budget and dealership prices are out of the question.

Thanks so very very much.

John
 

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2002 chevy trailblazer_lt
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1,243 Posts
Hi, this is as close as I can get to a forum for my problem.

Recently - along with several other problems, my 4wd selector switch and possible the entire transfer case system, went sideways. The first was the little dash light top right that shows a 4wd issue came on. It is intermittent. O'Reilly's scanner detected no codes. (Not shocked.) The next indication (not at the same time) was when starting up, as usual, the 4 LEDs flash and normally goes to 2WD. It instead showed 4wd low. I tried moving the selector back and both to different positions - the selection will flash (i.e. auto) but then never light up and it stays at 4wd low. Sometimes when starting all the lights flash then all go out and I get nothing. It appears to drive normally most of the time. Sometimes it does drive like it is 4wd hi.

Along the way the selector knob on the switch broke off so it now has a new switch thanks to NAPA. Not expecting it to solve the problem - it did not, but at least I can now try switching again.

I tried the trick of pulling fuse 8. No luck
I tried the trick of after starting, shifting to neutral. No luck.

Recommendations on what I should go after next?? TCCM?? Actuator on transfer case? Working on a budget and dealership prices are out of the question.

Thanks so very very much.

John
First thing, if there is a service 4wd light on, there is a code. If Oriellys or whoever can't see it then they have the wrong scanner. It's there. That's why the light is on.

What can you do about that?? Not a damn thing! So let's move on.

Don't have one of those small bluetooth OBD2 adapters do you?? Guessing not so will talk of doing it the old school way.....

If the indicator light is reading 4Lo then it is very likely getting a bad signal back from the shift motor sensor. If you have a multimeter and know how to use it then you can test the voltage signal from the shift motor sensor back to the TCCM through the dashboard side access panel. You will need a small probe like a sewing needle or a piece of small gauge solid copper wire to probe into the connector at the TCCM. The signal from the shift motor position sensor is the one labelled "brn/wht C1, B6 Encoder Signal" in this picture....

57371


Here is the access panel....

57372



The voltage returned should be close to these values....

Mode Switch Return VoltageEncoder Return Voltage
4Lo1.590.77
Neutral0.851.6
2Hi4.062.75
A4WD3.223.15
4Hi2.423.84
 

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WOW!!!! Thanks for the response. I opened the panel and found the connectors. Have meter but it is in the Motorhome which is at the repair shop. Will get the meter and check likely over the weekend. Thanks again. Have a great weekend.
 

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Hi, this is as close as I can get to a forum for my problem.

Recently - along with several other problems, my 4wd selector switch and possible the entire transfer case system, went sideways. The first was the little dash light top right that shows a 4wd issue came on. It is intermittent. O'Reilly's scanner detected no codes. (Not shocked.) The next indication (not at the same time) was when starting up, as usual, the 4 LEDs flash and normally goes to 2WD. It instead showed 4wd low. I tried moving the selector back and both to different positions - the selection will flash (i.e. auto) but then never light up and it stays at 4wd low. Sometimes when starting all the lights flash then all go out and I get nothing. It appears to drive normally most of the time. Sometimes it does drive like it is 4wd hi.

Along the way the selector knob on the switch broke off so it now has a new switch thanks to NAPA. Not expecting it to solve the problem - it did not, but at least I can now try switching again.

I tried the trick of pulling fuse 8. No luck
I tried the trick of after starting, shifting to neutral. No luck.

Recommendations on what I should go after next?? TCCM?? Actuator on transfer case? Working on a budget and dealership prices are out of the question.

Thanks so very very much.

John
Just one more poker in the fire ---- this is sometimes a problem being created where a problem doesn't really exist ---- except in the driver.

If you don't set the parking brake first THEN put the transmission in PARK --- you allow a lot (or a little) pressure on the drivetrain because the transmission is the device that is holding the car and with pressure on the parking pawl, you will be putting pressure on the front axle slider - yoke - actuator - the transfer case actuator and possibly both driveshafts.

No wonder the system fails and starts blinking dash lights!

The trick of going to neutral can actually help many times - but that's a great big clue that the driveline is bound up by the vehicle trying to roll against the Park pawl in the transmission - when the parking brake has not been applied.

Parking ---> with foot on service brake ---> apply Parking brake FIRST - then put transmission in PARK. - lock car and walk away.​
Driving away ---> with foot on brake --- start engine --- Put transmission in gear - release the Parking brake and then drive away.​
<I give them instruction books and they tear off the covers and eat the pages> <sigh>
 

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Just one more poker in the fire ---- this is sometimes a problem being created where a problem doesn't really exist ---- except in the driver.

If you don't set the parking brake first THEN put the transmission in PARK --- you allow a lot (or a little) pressure on the drivetrain because the transmission is the device that is holding the car and with pressure on the parking pawl, you will be putting pressure on the front axle slider - yoke - actuator - the transfer case actuator and possibly both driveshafts.

No wonder the system fails and starts blinking dash lights!

The trick of going to neutral can actually help many times - but that's a great big clue that the driveline is bound up by the vehicle trying to roll against the Park pawl in the transmission - when the parking brake has not been applied.

Parking ---> with foot on service brake ---> apply Parking brake FIRST - then put transmission in PARK. - lock car and walk away.​
Driving away ---> with foot on brake --- start engine --- Put transmission in gear - release the Parking brake and then drive away.​
<I give them instruction books and they tear off the covers and eat the pages> <sigh>
Thank you for offering no assistance at fixing the problem only what may have caused it.

Hope you have a wonderful day
 

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You want me to come on over and explain the big words for you?

The answer is in my response ... don't do what I told you not to.
 
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