NEED HELP 03 TB 4x4 not working at times but not disconnect

[Codylop]

Hello,
Quick background on TB. I purchase the trailblazer two months ago as a work vehicle, but starting to enjoy it. I plan on installing a leveling kit and some other tasteful mods.
Trailblazer has 170,000 miles.

Started doing maintenance and repairs(ignition coils,abs module,new speakers,and etc.)Transmission was replaced 10,000 miles ago(have receipt for transmission replacement from a gmc dealer in glove box)and I also checked transfer case oil it looks new and full. I'm not sure but I'm guessing it was change with transmission.

The problem and/or question is with the 4x4 system. Every so often in the morning(not every morning) when I get in to start the truck I would notice the 4x4 switch 2hi is blinking and the neutral light is on. If I move the transmission lever to neutral it will come back to 2hi with a solid light and the red neutral light also turns off with out touching the 4x4 switch. Drives just fine and operate as one should.

The other problem is the 4x4 not engaging all the time. I followed the instructions on this site and this is what I got, however when it does work I can feel the steering wheel get harder to turn and less wheel spin in the snow. I'm in Missouri and just got some snow.

With just the passenger front tire off the ground, I can turn the system from 2hi to 4hi and I'm getting the front 4x4 disconnect to work properly (tire will spin in 2hi and not in 4hi)every time. I can hear the motors on the disconnect and transfor cases working.

The weird thing is the driver side wheel.
At first when lifting the driver side wheel and putting the system in 4hi it spins freely with the front prop shaft to the transfer case also spins, but if I turned the system back to 2hi then back to 4hi a couple of time I might get it to stop spinning . As in the transfer case engaged the clutches and 4x4 will work now.
So is this the encoder motor on the transfer case bad?
I also don't have the 4x4 service light on,however I did check with my obd2 reader and no codes there.
Thanks.

 

[Codylop]

Update. Checked for play at front axle disconnect and theres play in cv shaft at disconnect. Not much but more then it should. I'll change disconnect when I can.

In the morning, every day this week, it is doing the neutral light on and 2Hi flashing on the switch. If I put the transmission in reverse it will go in reverse and work fine but the 4x4 switch will still flash 2Hi and show neutral light. Is not until I put the transmission in neutral that the 4x4 switch will stop flashing the 2Hi and the neutral light will go off. I do hear the transfer case motor running when it does this.

One other thing, I tried auto 4HI in my driveway. The driveway was iced over and step up hill to the main road.
When in A4HI and in reverse(backing out of driveway) if the rear wheel would start slipping the transfer case would hit the clutches or front wheels for a half second then stop.

I'm thinking the brake in the transfer case motor encoder is bad. With a loose bearing in the front disconnect.

 

[Chickenhawk]

Could be possible there are multiple problems. I would start by replacing the switch itself. Cheap and easy fix, and they do go bad, especially if not used regularly. The encoder is probably next, but I would save the disconnect for last. Based on my own experience chasing a similar problem, there is always a certain amount of play in the shaft. The disconnect is also the most difficult repair of the three and sometimes takes a very BFH to remove.

 

[Codylop]

Could be possible there are multiple problems. I would start by replacing the switch itself. Cheap and easy fix, and they do go bad, especially if not used regularly. The encoder is probably next, but I would save the disconnect for last. Based on my own experience chasing a similar problem, there is always a certain amount of play in the shaft. The disconnect is also the most difficult repair of the three and sometimes takes a very BFH to remove.

Thanks.
What brand for switch and encoder motor? I see Dorman is every where but see bad reviews on Dorman encoder motor.
I used a Dorman ABS module and is great so for.

 

[TJBaker57]

Do you happen to have a Bluetooth OBD2 reader, the kind used with Torque Pro, DashCommand, OBD Fusion or the like??

If you did I could likely show you how to read the encoder position sensor and you could see what was going on down there during these flashing 2Hi/Neutral events

 

[Codylop]

Do you happen to have a Bluetooth OBD2 reader, the kind used with Torque Pro, DashCommand, OBD Fusion or the like??

If you did I could likely show you how to read the encoder position sensor and you could see what was going on down there during these flashing 2Hi/Neutral events

I do and I use OBD Fusion.

 

[TJBaker57]

I do and I use OBD Fusion.

So to do this we need to know the TCCM Part# and Operating system number and the Calibration number of the TCCM in the truck.

No need to get into the dashboard, we can read these with OBD Fusion.

Go to user-defined PIDs and add an entry like seen here. The pictures are the settings for reading out the part number. No need to make separate entries for the operating system and calibration as we can just edit this same entry and hit the TEST button for the other values. Where you see "08" is the address of the data block that holds the part number. Change that to 0A for the operating system and 0C for the calibration number. In the images below 12580060 is the part number for the TCCM I am looking at right now.




The reason we need this is I am hoping yours will match one of the handful of TCCMs I have data on. You see, the TCCM doesn't support reading out it's data the way OBD Fusion and Torque Pro etc. do it. So I get the data by entering the information OBD Fusion will need to read out the data directly from the memory location it is in. I have scanned a number of different TCCMs and have read out the memory to find where they keep what I want. If yours is a match for one that I have scanned then we should be able to read out the sensor values from the encoder/motor and should be able to see if it's behaving or not.

 

[Codylop]

So to do this we need to know the TCCM Part# and Operating system number and the Calibration number of the TCCM in the truck.

No need to get into the dashboard, we can read these with OBD Fusion.

Go to user-defined PIDs and add an entry like seen here. The pictures are the settings for reading out the part number. No need to make separate entries for the operating system and calibration as we can just edit this same entry and hit the TEST button for the other values. Where you see "08" is the address of the data block that holds the part number. Change that to 0A for the operating system and 0C for the calibration number. In the images below 12580060 is the part number for the TCCM I am looking at right now.

View attachment 102943View attachment 102944View attachment 102945


The reason we need this is I am hoping yours will match one of the handful of TCCMs I have data on. You see, the TCCM doesn't support reading out it's data the way OBD Fusion and Torque Pro etc. do it. So I get the data by entering the information OBD Fusion will need to read out the data directly from the memory location it is in. I have scanned a number of different TCCMs and have read out the memory to find where they keep what I want. If yours is a match for one that I have scanned then we should be able to read out the sensor values from the encoder/motor and should be able to see if it's behaving or not.

Thanks. I'll do this and will report back.

 

[Codylop]

So to do this we need to know the TCCM Part# and Operating system number and the Calibration number of the TCCM in the truck.

No need to get into the dashboard, we can read these with OBD Fusion.

Go to user-defined PIDs and add an entry like seen here. The pictures are the settings for reading out the part number. No need to make separate entries for the operating system and calibration as we can just edit this same entry and hit the TEST button for the other values. Where you see "08" is the address of the data block that holds the part number. Change that to 0A for the operating system and 0C for the calibration number. In the images below 12580060 is the part number for the TCCM I am looking at right now.

View attachment 102943View attachment 102944View attachment 102945


The reason we need this is I am hoping yours will match one of the handful of TCCMs I have data on. You see, the TCCM doesn't support reading out it's data the way OBD Fusion and Torque Pro etc. do it. So I get the data by entering the information OBD Fusion will need to read out the data directly from the memory location it is in. I have scanned a number of different TCCMs and have read out the memory to find where they keep what I want. If yours is a match for one that I have scanned then we should be able to read out the sensor values from the encoder/motor and should be able to see if it's behaving or not.

 

[Codylop]

Got that on the 08 PID but 0A 0C would not work.

 

[TJBaker57]

Got that on the 08 PID but 0A 0C would not work.

Did it say something like "DATA ERROR" for the "0C" ??

I overlooked one setting for Torque Pro that is likely needed for the "0C" to work. The "0C" data block returns more data bytes than what most bluetooth adapters expect. So there is a special setup command for the bluetooth adapter to allow long messages. It is set in the "vehicle profile" editor in Torque Pro, seen here.....

 

[Codylop]

I'm on OBD Fusion and don't see this setting.

 

[TJBaker57]

I could take a guess that your 0C value will be 12581142.

If so then it is likely that the following will work for the encoder sensor return voltage..





This I believe is the raw value from the sensor. A Tech 2 tool returns a value from a similar setup but I think the Tech 2 setup returns a value that is somewhat massaged by software, maybe a short-timed average?? That location intruction for mode&pid would be 2300013D01 instead of 2300009501.

I also have several more parameters available for that unit # 12580060 as seen below....

 

[TJBaker57]

I'm on OBD Fusion and don't see this setting. View attachment 102983

Ah yes... OBD Fusion. I will look at my setup to see if I can determine what to do there. We might not need it though..

I think I remember that happening, but I could see the response in the test window in OBD Fusion and I could pick out the bytes I needed and did the decoding myself

 

[TJBaker57]

I just tried this out on my own 2002 using OBD Fusion. This is what a setup there would look like, except in your case change the 00009101 to 00009501.






This should return a value that closely corresponds to the following table for encoder return voltage....

 

[Codylop]

It worked!!! This log is from the encoder motor going from A4wd to 4Hi. You can see it try to get the volts where it needs it but can't hold it there. It looks like the brake on the motor is bad. I'll replace the transfer case encoder motor and recheck the volts. Thanks Tjbaker57!!!!

 

[TJBaker57]

I'm curious what it does during those times when it shows the neutral light and the flashing 2Hi

 

[Codylop]

I'm curious what it does during those times when it shows the neutral light and the flashing 2Hi

It looks like the neutral and 2hi are close in volts. I'm not sure if they are close together in the gear selector but I'm guessing they are.
If the brake in the motor is bad, can it go between the two or just enough to send the wrong volts back?
I'll try to check it when its doing the neutral light and 2hi flashing in the morning,however it only does this in the morning sometimes. Thanks again!!

 

[TJBaker57]

It looks like the neutral and 2hi are close in volts. I'm not sure if they are close together in the gear selector but I'm guessing they are.
If the brake in the motor is bad, can it go between the two or just enough to send the wrong volts back?
I'll try to check it when its doing the neutral light and 2hi flashing in the morning,however it only does this in the morning sometimes. Thanks again!!

Yes, you can tell by the voltages where the positions are! Neutral is when the encoder motor turns the transfer case shaft fully counterclockwise and 4Hi is fully clockwise. It doesn't spin all around, the full rotation from 4Lo to 4Hi is only like 80° or so.

 

[TJBaker57]

I generally expect a little variance in the exact voltage, but I watch for the reading to be somewhat stable once in a particular mode. A reading that jumps around suggests a failed sensor or bad connection somewhere. My own 2002 had a cracked solder joint in the sensor.

The brake is spring loaded to the ON (locked) position and requires power from the TCCM to release.

 

[TJBaker57]

I also discovered where the "AT AL" instruction goes in OBD Fusion..

 

[TJBaker57]

It worked!!! This log is from the encoder motor going from A4wd to 4Hi. You can see it try to get the volts where it needs it but can't hold it there. It looks like the brake on the motor is bad. I'll replace the transfer case encoder motor and recheck the volts. Thanks Tjbaker57!!!!View attachment 102992

And Thank You for playing along!! You are I believe the first to make use of this particular focus of my efforts!

 

[Codylop]

And Thank You for playing along!! You are I believe the first to make use of this particular focus of my efforts!

Thanks. It was kool and crazy to see what can be done with OBD Fusion and a Bluetooth reader.
I bought this setup two years ago for my e46 BMW and never thought it could do more.
I end up buying a Harbor freight OBD reader recently so I can read the abs codes on the TB but for $175 I feel I paid to much.

 

[Codylop]

Thanks. It was kool and crazy to see what can be done with OBD Fusion and a Bluetooth reader.
I bought this setup two years ago for my e46 BMW and never thought it could do more.
I end up buying a Harbor freight OBD reader recently so I can read the abs codes on the TB but for $175 I feel I paid to much.

Here is another log. This one is from A4Hi to 4Hi in more detail.

 

[TJBaker57]

View attachment 102995
Here is another log. This one is from A4Hi to 4Hi in more detail.

So varying a couple tenths of a volt isn't a great deal. But I think I would expect to see at least a half volt difference between A4WD and 4Hi. For example, today my 2002 was reading about 2.63 in 2Hi in the drive home. Once home I switched to 4Lo then back to 2Hi and it settled at 2.73 for 2Hi. The number will likely have some drift to it and I imagine it can also vary between different TCCM particulars. Mine is a 2002 with the factory original TCCM. Many have been updated to different part numbers like yours. There were a raft of small changes made to the TCCM firmware in the early years as they made adjustments for this & that. Before passing judgement or making a diagnosis I would observe the operations over a range of shifting and see what shows up.

 

[Codylop]

Was able to catch it doing the neutral light this morning. Volts were lower then 2hi but not all the way down to neutral volts. See log. Volts did jump up to 2hi when I put the transmission in neutral and it switched.

 

[TJBaker57]

Since we now can see that the encoder seems to be functional, it moves when commanded by the TCCM, and the voltages, while not where we expect them to be at times, look stable, I would have a look at the mode switch also. Particularly since you now know how to set it up in OBD Fusion. Just add another PID and change the name for that one to be TCCM Mode switch. The rest of the setup is the same except use 00009401 instead of 00009501.

For anyone following along, the values 00009501 and 00009401 are for the TCCM part # 12580060 with OS# 12580062 and Cal # 12581142. They also work for part# 12584313 with a different OS# but the same Cal#, but not for other part##. These memory locations are slightly different for various TCCM part, OS, and calibration numbers. I have tested 5 different TCCMs and have the data points for those. We use the memory locations directly because the TCCM does not offer the option of requesting this data by the normal "PID" number.

 

[Codylop]

Here's the TCCM switch log. Going from 2Hi to A4Hi then 4Hi. I'll upload some more in a little.

 

[Codylop]

Here is the switch sitting in 2Hi. You can see the volts jumping. I know is not much but it shouldn't be doing this.

 

[Codylop]

Here is the Encoder and the switch volts. This is from 2hi to A4Hi then 4Hi.
It looks like the brake on the motor is bad. You can see in 4Hi is keeps trying to up the pressure on the clutches but comes back down. At the same time the switch volts is the same.

 

[Codylop]

Since we now can see that the encoder seems to be functional, it moves when commanded by the TCCM, and the voltages, while not where we expect them to be at times, look stable, I would have a look at the mode switch also. Particularly since you now know how to set it up in OBD Fusion. Just add another PID and change the name for that one to be TCCM Mode switch. The rest of the setup is the same except use 00009401 instead of 00009501.

For anyone following along, the values 00009501 and 00009401 are for the TCCM part # 12580060 with OS# 12580062 and Cal # 12581142. They also work for part# 12584313 with a different OS# but the same Cal#, but not for other part##. These memory locations are slightly different for various TCCM part, OS, and calibration numbers. I have tested 5 different TCCMs and have the data points for those. We use the memory locations directly because the TCCM does not offer the option of requesting this data by the normal "PID" number.

Can you log your Volts on your TCCM to see if is close to what I posted?
It would help to see what a proper functioning 4x4 is doing. Thanks.

 

[TJBaker57]

I think some "jitter" in the switch as well as the encoder sensor is somewhat normal. My switch does that too. You may remember back at post #13 I mentioned that the Tech 2 uses a different address of this data. The alternate addresses are in the last picture attached there. I sort of remember back when I was working these things out that the other address seemed smoothed out without the signal jitter.

Your encoder signal does look a little goofy. Starts out lower than it should be at 2Hi and the fall off from the 4Hi is odd.

The jump up to A4WD with a little adjustment back down I think is normal behaviour. I see the same sort of punch-up then fall back behaviour in things like the exhaust cam phaser solenoid. It's like punching the gas pedal to get to where you need to be but then pulling back when you get there. Does that make sense?

 

[Codylop]

I think some "jitter" in the switch as well as the encoder sensor is somewhat normal. My switch does that too. You may remember back at post #13 I mentioned that the Tech 2 uses a different address of this data. The alternate addresses are in the last picture attached there. I sort of remember back when I was working these things out that the other address seemed smoothed out without the signal jitter.

Your encoder signal does look a little goofy. Starts out lower than it should be at 2Hi and the fall off from the 4Hi is odd.

The jump up to A4WD with a little adjustment back down I think is normal behaviour. I see the same sort of punch-up then fall back behaviour in things like the exhaust cam phaser solenoid. It's like punching the gas pedal to get to where you need to be but then pulling back when you get there. Does that make sense?

Yes it does.. I'll try to catch it doing the neutral light in the morning but its looking like I need to change the encoder motor.

 

[TJBaker57]

Another thing I'd be curious about is what do the switch and encoder signal voltages read when you have that flashing at 2Hi and neutral light on happening.

I'll see about recording some data on mine tomorrow.

 

[Codylop]

Ok thanks.

 

[TJBaker57]

So I can't remember why I was going to record data for today!! But I grabbed some anyway. I used a different app that is better for this task, Car Scanner ELM OBD2 Pro.



Green is the mode switch
Red is the encoder
Blue is the front axle lock indicator

I accidentally placed the mode switch between two selections once. Several indicator lights flashed but no shifting until I saw the error and corrected the switch position.

Seeing the bigger picture here one can see why a small jitter of either mode switch or encoder signal likely isn't a big issue in light of the full range of values and the separation between selections.

 

[Codylop]

So I can't remember why I was going to record data for today!! But I grabbed some anyway. I used a different app that is better for this task, Car Scanner ELM OBD2 Pro.

View attachment 103004

Green is the mode switch
Red is the encoder
Blue is the front axle lock indicator

I accidentally placed the mode switch between two selections once. Several indicator lights flashed but no shifting until I saw the error and corrected the switch position.

Seeing the bigger picture here one can see why a small jitter of either mode switch or encoder signal likely isn't a big issue in light of the full range of values and the separation between selections.

Thanks. I wanted the log, to see what a good working 4x4 would do.
I see that your encoder doesn't do the over shot in 4HI like mine is.
I'll get a dorman encoder from O'Reilly.
I want the GM replacement but they discontinue it.

 

[Codylop]

Replaced transfer case motor today.
Man that plug was a painful. Everything looks to be 100% now. I'll post a log.

I was able to catch it doing the neutral light one morning. It was cold and I was in a hurry so no log but I was able to look at the volts.
The 4x4 switch volts was normal but the encoder was down to 2.3ish volts. I had to put the transmission in neutral then switch the 4x4 switch to A4Hi back to 2Hi for it to move the encoder motor back to 2.8 volts. Thanks for everything.

 

[Codylop]

Here is the log with the new transfer case motor. You can see when switching to 4Hi it no longer comes back down and its holding volts are higher.
There's a chance of snow next week. I'll update the post after the snow about how the 4x4 is working.

 

[Codylop]

Everything is working!!
No longer doing the neutral light in the morning and 4x4 is working properly!!! Thanks TJBAKER57!!!