NEED HELP Transfer case encoder co327 problems

matty8412

Active Member
Hello everyone. I'm seriously in need of some answers about my 2006 chevy trailblazer EXT LT 4.2L I6.
So we came back from camping and a couple days later we had the service four wheel drive light come on. I had the truck scanned at a mechanic shop and came back that my decoder motor was non recognizable. So I bought a new ACDelco decoder motor and installed it. Ever since, the truck has been in 2wd but stuck in first gear. Service 4x4 light is still on and no lights on the selector switch. I had pulled the #8 fuse and waited 30 minutes. After 30 minutes I plugged the fuse back in and still nothing. I've been throwing so much money at this truck with no fix. All fluids have been changed with the specific fluids for everything. Really puzzled here and we really need our truck back on the road.
Any help will be greatly appreciated
 
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Mooseman

Moderator
A quick Google search found me this:

And a google search of this site gives lots of threads on that code:

So the service AWD light comes on as soon as the ignition is on or just when you try to shift it?
 
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matty8412

Active Member
Both. Turn the key and the service 4x4 warning comes on and all the lights start blinking on the selector switch and then they all go out except the warning light. Even after doing a reset. Co 327 is the only code the technician found. I'm wondering if I need to get the tccm flashed at a gm dealership and see what happens. I did get told by a transmission tech that I can manual turn the shaft on the t-case all the way counter clockwise to set it in 2wd but I cant shift out of 1st gear. Even at 3500rpm she wont shift gears. I'm just hoping it's not anything internal in the t-case.
 

Mooseman

Moderator
Although it didn't give a final resolution, this thread does give a full description of the code and what can be done to possibly correct it.


Since you encoder motor is new, I would suspect a wiring issue.
 

TJBaker57

Well-Known Member
Frankly, I don't see (or know of) a connection between the C0327 code and a transmission that won't shift out of 1st gear.
 

TJBaker57

Well-Known Member
Off the top of my head...I would be looking at the speed sensor(s) on the transmission in the area where the encoder motor was changed. If the wiring to these was disturbed or broken then the computers don't know how fast they are going and won't shift right, or so I would expect. I seem to remember a service bulletin on these speed sensors as well, having to do with the wiring which are twisted pairs and have been subject to degradation on some vehicles. The bulletin even called for replacing some of that wiring if need be.
 

MRRSM

Lifetime VIP Supporter
While occurring on a different Truck Platform Forum...conceptually... and almost to the point of exhaustion... The C0327 Diagnosis and Solution are discussed from all possible angles that may prove helpful in this instance as well:

 
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matty8412

Active Member
Off the top of my head...I would be looking at the speed sensor(s) on the transmission in the area where the encoder motor was changed. If the wiring to these was disturbed or broken then the computers don't know how fast they are going and won't shift right, or so I would expect. I seem to remember a service bulletin on these speed sensors as well, having to do with the wiring which are twisted pairs and have been subject to degradation on some vehicles. The bulletin even called for replacing some of that wiring if need be.



So now I have a new decoder motor on and I reset the computer by unplugging the battery. Pulled the #8 fuse for 30 minutes and plugged back up. I then put the #8 fuse back in and turned the key. No warning light up on the dash and the light came on the selector switch. I then turned the selector switch to 4hi and then started the truck. Tried putting her in reverse but nothing happens. Put her in drive, nothing happens. It seems to me that the transfer case is stuck in neutral. The dash warning light came on and now the selector switch has no lights on at all. I tried to reset the computer again with no results. From this morning truck only had 2wd but wouldn't shift out of first and now with the new decoder motor on and after a complete disconnect reset, the t-case is stuck in neutral. Any ideas now? Anyone?
 

Mooseman

Moderator
Take the encoder motor off and try to move the shaft on the TC with vice-grips. I can't remember in which direction does what though. I think turning it to the left takes it to 2WD. Hopefully your TC is OK.

The way you are supposed to do it is to first start the truck and then move the selector. 2LO is kinda different in that you have to move the truck a little to get it to shift in and out of it.
 
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matty8412

Active Member
But the encoder motor wont go back on after I manually shift the t-case shaft. How will I get the encoder back on? Can I take the encoder motor and physically turn the cogs in order for everything to line up? I dont want to damage the new encoder motor
 

Mooseman

Moderator
With the encoder removed but still connected, turn on the ignition and turn the selector to 2WD. You should then be able to get it on the TC shaft.
 
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matty8412

Active Member
That's what I tried and nothing happened. The 2wd light was on steady and the service light was back on. The encoder was not connected to the tc and did not move at all. I hope the new decoder motor isn't fried. That just cost me $300 in the hole. I'm at the point of of putting her on a trailer and bring it to the nearest tranny shop that is 1 hour away. But then is it worth it?
 

Mooseman

Moderator
You should be able to shift it to 2WD to drive it with the encoder motor removed. If you can't shift it to 2WD, then I'm afraid that the transfer case may be broken. I'd just get one from a pick-n-pull or a used one somewhere. They're not prone to failure unless they're not maintained.

If the encoder motor isn't moving at all, I think it might be your TCCM. You can pick one up cheap from a pick-n-pull. Get one from an 03+ TB or Envoy. 02 had a defect.
 
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matty8412

Active Member
I will give her my best. I really do hope that it is not the t case. She was such a great truck before all this started to happen to her
 

budwich

Well-Known Member
Probably too late at this point... hope you got this address and wasn't too expensive.
Did you check the connector for proper electrical conditions? It "sounds like" there is some signal loss going into or out of the encoder and as result, the vehicle "thinks" its in or needs to be in 4w low which I think locks the tranny at 1st.
 
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matty8412

Active Member
Probably too late at this point... hope you got this address and wasn't too expensive.
Did you check the connector for proper electrical conditions? It "sounds like" there is some signal loss going into or out of the encoder and as result, the vehicle "thinks" its in or needs to be in 4w low which I think locks the tranny at 1st.
Hello budwich. Unfortunately the issue has not yet been resolved. This is damn frustrating since I have spent lots of money without no gain. I bought a new encoder motor and had a technician come out with his scan tool and came back with a code C0306. And i have been given these links stating that it was a short to ground including circuit A/ circuit B. So I went back to the parts shop and got another brand new encoder motor. But this "new" encoder motor had 4 used bolts in the box and did not come with a plastic tool device in the slot that the shaft of the tcase stabs into as the first one did have that plastic tool. I'm thinking this 2nd new encoder motor is a rebuild or one that someone tampered with and brought it back like that. I don't have the cash to bring it in to the dealership/stealership. I've also checked the ground wires and they tested positive. If I cant get this trailblazer issue solved, my last resort to to actually send it to the Hutterites. They told me that they can definitely fix it and would be nowhere as expensive as the dealership. Sounds funny but they know what they are doing since all their vehicle's are bowties and nothing else. I would love to check the electrical connections but I have 0 (zero) experience with electrical. I've been told many of times that a little knowledge can cause a lot of damage. So I stay away from that. If someone can sort of teach me what to do I can maybe then try. I live almost 2hours from town and cant afford to bring the truck in. Thanks for all the help in advance. Much appreciated.
 

budwich

Well-Known Member
Hello budwich. Unfortunately the issue has not yet been resolved. This is damn frustrating since I have spent lots of money without no gain. I bought a new encoder motor and had a technician come out with his scan tool and came back with a code C0306. And i have been given these links stating that it was a short to ground including circuit A/ circuit B. So I went back to the parts shop and got another brand new encoder motor. But this "new" encoder motor had 4 used bolts in the box and did not come with a plastic tool device in the slot that the shaft of the tcase stabs into as the first one did have that plastic tool. I'm thinking this 2nd new encoder motor is a rebuild or one that someone tampered with and brought it back like that. I don't have the cash to bring it in to the dealership/stealership. I've also checked the ground wires and they tested positive. If I cant get this trailblazer issue solved, my last resort to to actually send it to the Hutterites. They told me that they can definitely fix it and would be nowhere as expensive as the dealership. Sounds funny but they know what they are doing since all their vehicle's are bowties and nothing else. I would love to check the electrical connections but I have 0 (zero) experience with electrical. I've been told many of times that a little knowledge can cause a lot of damage. So I stay away from that. If someone can sort of teach me what to do I can maybe then try. I live almost 2hours from town and cant afford to bring the truck in. Thanks for all the help in advance. Much appreciated.
Its been a while since I changed out my tran case motor... but its pretty simple. There are two wires for motor control, two for reading the position and two for "brake control"

your problem is UNLIKELY to be the motor since you have tried at least two (if I understand the "dialog" so far).

Further, your previous post:
QUOTE: "That's what I tried and nothing happened. The 2wd light was on steady and the service light was back on. The encoder was not connected to the tc and did not move at all. I hope the new decoder motor isn't fried. That just cost me $300 in the hole. I'm at the point of of putting her on a trailer and bring it to the nearest tranny shop that is 1 hour away. But then is it worth it?"
kind of points out the problem. As was suggested, mechanically disconnect the motor from the transfer case and cause it to move by using the switch on the dash to set the motor to align with the position of the shaft of the case WHICH you need to ensure is in the "right" position as stated previously (most likely 2W). "

You indicated that you have moved the shaft to the right position... confirm that this is true and INDEED you have moved it by hand... this is to ensure that the transfer case is indeed mechanically happy. IF you can't move the shaft by hand, I do believe this is mechanical issue in the case.... and that's a more significant problem than the encoder motor.

what does this mean... "I've also checked the ground wires and they tested positive." especially when you say you have ZERO electrical experience.... :-(

ONE IMPORTANT NOTE: I do believe there is nothing stopping the encoder motor turning "all the way around" when not mounted to the transfer case and I think this can cause problems if not carefully when powering the motor when not mounted... was there warning labels on the unit?
 
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matty8412

Active Member
Its been a while since I changed out my tran case motor... but its pretty simple. There are two wires for motor control, two for reading the position and two for "brake control"

your problem is UNLIKELY to be the motor since you have tried at least two (if I understand the "dialog" so far).

Further, your previous post:
QUOTE: "That's what I tried and nothing happened. The 2wd light was on steady and the service light was back on. The encoder was not connected to the tc and did not move at all. I hope the new decoder motor isn't fried. That just cost me $300 in the hole. I'm at the point of of putting her on a trailer and bring it to the nearest tranny shop that is 1 hour away. But then is it worth it?"
kind of points out the problem. As was suggested, mechanically disconnect the motor from the transfer case and cause it to move by using the switch on the dash to set the motor to align with the position of the shaft of the case WHICH you need to ensure is in the "right" position as stated previously (most likely 2W). "

You indicated that you have moved the shaft to the right position... confirm that this is true and INDEED you have moved it by hand... this is to ensure that the transfer case is indeed mechanically happy. IF you can't move the shaft by hand, I do believe this is mechanical issue in the case.... and that's a more significant problem than the encoder motor.

what does this mean... "I've also checked the ground wires and they tested positive." especially when you say you have ZERO electrical experience.... :-(

ONE IMPORTANT NOTE: I do believe there is nothing stopping the encoder motor turning "all the way around" when not mounted to the transfer case and I think this can cause problems if not carefully when powering the motor when not mounted... was there warning labels on the unit?
So I am able to move the t case shaft by hand with no problem. The way I tested the grounds was with a test light. Having the alligator clip end connected to the positive battry post and the test light on the ground wire on the cab mount under the driver seat underneath the truck. I have read that there is a ground under the battery tray as well and another ground on top if the driver side a arm. I have not tried to check voltage on the pig tail connector that the tcase motor connects to. I didnt want to risk frying something that I would regret.
 

TJBaker57

Well-Known Member
The code tells you there is a problem with the circuit. The code does not identify exactly what. May be the motor, may be the wiring, may be a bad connection. Has the actual wiring been checked with a meter and verified??

Edit: wiring diagram calls out a ground on the firewall for this circuit as well
 

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budwich

Well-Known Member
OK... thanks. so that indicates that the transfer case is "mechanical functioning" in some form and not bound up internally such that the encoder motor can not move it.

Your test of the ground is OK assuming that those are the grounds being used. I would suggest you get a meter and do some reading on how to measure voltage and resistance with one. You are likely dealing with an electrical problem basically with "both eyes closed"... your chance of success is minimal. Learning... there is nothing magically about a meter. You likely have everything you need. A regular battery to practice how to read voltage and a light bulb to practice how to read resistance.

As mentioned, it is likely that no / little power is getting to the motor to cause it to turn. So you need to check those pins in the connector to see if there is voltage and ground there.

The pin "pair" will need to have ground and power one way and then opposite the other way to turn the motor back... standard normal dc motor operation. I do believe that the wires have some form of voltage on them at "all times" (key on) because that's how the system does its checks to cause the DTC.
 
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budwich

Well-Known Member
I see further that IF you have dtc0327, "all motor activity stops". Basically, you need to check for the presents of 5v in the GY wire. Go from there.
 

Mooseman

Moderator
I would do a continuity check for each wire from the TCCM to the encoder motor. I would also check those going to the disconnect just to be sure. The wiring diagram posted above should help with that.
 

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