05 Trailblazer with code C0327 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > 4x4 Drivetrain

4x4 Drivetrain 4x4 Repairs & Problems

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  #1  
Old 02-04-2009, 07:30 AM
Tyler101 Tyler101 is offline
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2005 Chevy TrailBlazer LT
Indigo Blue Metallic 4.2L I6 AWD
Join Date: Feb 2009
Location: Ottawa, ON
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05 Trailblazer with code C0327

Wifes trailblazer had the service light come on and would no longer switch through the 2wd, awd,4hi,4low while the vehicle was running. You were able to switch the vehicle off turn the switch to another option restart the truck and the vehicle would switch and you would have the light above the switch indicating your selection. All lights above the indicator are now off and it does not appear to switch at ALL. Tried pulling the fuse #8 for 30min to wake up the TCCM but no luck.

Took it to a small garage and they pulled the Co327 code and wanted $1500 to repair. I did some research and it looks like I need either the TCCM or the Encoder motor or both. I am going to do the repair myself and just want to know the correct part numbers to order. I live in Canada and will either source from up here or if the price is significantly better through somewhere like gmpartsdirect in the US.

There seems to be some confusion on whether or not you have to take the vehicle after the swap to the dealer to have software loaded?
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  #2  
Old 02-10-2009, 12:59 PM
bandy47 bandy47 is offline
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4wheel drive inoperable

I have an 02 Envoy which had a similar problem. My fix was diagnosed at the dealer as being the Transfer case control module (tccm). The part was identified, which they would sell me for $355 (discounted because I am a GM employee- retired). And they would charge me only1 hour of labor to reprogram it since I already paid for the diagnosis of .5 hr at 92.00/hr or $46.00 instead of 2 hours of labor. Well this didn't seem right to me to have to pay for computer programming a module at a labor rate. So I asked if they would consider letting me procure the part myself from a GM service parts operation at the regular employee discount and just have it reflashed at the dealer. At first the service write-up guy said sure thing,but after a quick conference with the service mgr. backed out of the agreement and said that they would not reprogram the part either if I replaced it myself.
I decided this was not someplace I wanted to do business with and left. I subsequently got the information of part no. (12590220) price for gm employee= 155.94 plus tax. I found out that reprogramming is not be necessary. I searched a few junkyards in my local area and found the part for $75.00 plus tax at Middletons Autoparts in Fraser Mi. and the guy even put it in my dash as a favor. I drove out of the parking lot with my 4 wheel drive and the dash light indicators working. I'm sorry to say GM service dealers embarass me.
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  #3  
Old 02-10-2009, 01:11 PM
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KHill KHill is offline
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Bandy here basically covered it. If you can get the TCCM on the cheap, I don't see why the dealership would have to reprogram it becasue it works within the 4wd system and not with the PCM or other computer components. The only thing I would possibly consider elsewise is that there have been reports of the dash switch causing this problem as well. Make sure all the contacts are clean in the system and then go for the part. Living in Ottawa, you definitely don't want this problem getting any worse this time of year.


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  #4  
Old 02-10-2009, 01:40 PM
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C0327 is an encoder motor feedback failure, not likely involved with the switch at all. An open wire in the connector or wiring harness from the TCCM to the encoder motor could also cause that.

If all indicator lights on the switch are off, do you have the Service 4WD light on?

You can get encoder motors and TCCMs off Ebay or junkyards. Without some additional troubleshooting with a meter or a tech tool at the dealer, I don't know of a way to tell it's one or the other. Do you have any trailblazer or envoy owners nearby to trade TCCMs with?

Finally, the details about the need for reflashing the TCCM at the dealer is as follows: The TCCM needs to know what gear ratio is in the vehicle so it can make some calculations about the algorithms in A4WD mode. It also needs to know if it's in an AWD or 4WD vehicle because the AWD ones don't have a front axle actuator, or a control switch at all. They're always in AWD mode.

A used TCCM has been flashed at the factory with the VIN of the vehicle it was in, and if that vehicle matches yours, no problem. If the gear ratios are different, you'll peobably never notice the difference in A4WD performance, either.

A blank TCCM that's never been flashed, may not operate at all, and the backyard mechanic may conclude it was DOA.

That's why a dealer reflash/reprogramming may or may not be necessary for all TCCM replacements.

That $1500 proposal was just ludicrous, unless the mechanic has three kids all in law school at the same time. He definitely was going to shotgun it.
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  #5  
Old 02-20-2009, 11:04 AM
Tyler101 Tyler101 is offline
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A little update and still pretty frustrated...

The Service 4wd light was on, with no lights above the switch indicator. Borrowed a friends 03 trailblazer to do some swapping to pin point the problem. Started with the TCCM, mine worked in the 03, theirs had no change in mine (still not working service light still on). Tried while I had the dashes out the switch as it was a 2min check. Still no change, mine worked in the 03. Now left with just the Encoder motor as the problem. Struggled to get mine off as it seemed that it was still under a load of sorts. Vehicle was in 2wd. Could not get the old motor back on as the key was off and would not turn in the encoder motor. So I ordered a new one off ebay, got it yesterday. BTW the GM retail in Canada is $1068, got mine for $200 CND off ebay....plug it all in and bolt the encoder motor on. Turn the key in the ignition and all service lights are off now and the switch light is good and working. Changing the positionl, the light moves and you can hear the actuator moving clearly. Thinking GOOD to GO now! Put the dash all back together bolt the belly pan back up, back it off the ramps all happy. Down the driveway in the snow (fresh 3 inches from last night) definetly in 2wd as I spin a bit. Shift to N, change the switch to 4HI everything does what is suppose to it seems, but the vehicle spins as it remains in 2wd? Now the service 4wd lights are on again, and the dash switch has no lights....right back to where I started but a few dollars shorter in the wallet. Any ideas before I light it up
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  #6  
Old 02-20-2009, 11:49 AM
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the roadie the roadie is offline
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Sounds like the encoder motor is working but the front axle actuator is not. I'm not sure how much you searched and read before your first post, but I've posted a few times about listening for the sounds of the two different motors before. One easy way to confirm the encoder motor is running is to reset the TCCM by pulling and inserting the fuse (1 minute should be plenty), then try 4LO. It's easy to tell if the TC has started using the 2.7-to-1 reduction ratio.

Listening to the noises is like this:

You can do this in neutral, with the key on but the engine NOT running.

The encoder motor is a lower pitched noise that lasts a bit longer than the actuator. It runs in all three possible mode transitions. From 2WD->A4WD, from A4WD->4HI, and from 4HI->4LO.

The front axle actuator is a 2 second higher pitched whine, and it ONLY makes a noise when going into or out of 2WD.

The actuator can work fine when removed from the vehicle, yet stall out the motor due to internal problems in the splined disconnect that it works on, or congealed grease and low temperatures, or grease that gets on electrical slide contacts inside. I posted disassembled pics of this when I fixed Teebes' vehicle last year. Lots cheaper than a new actuator as long as you enjoy taking things apart to the lowest possible component level.

If yours worked fine for the first time, and you had no service 4WD light, then it WAS working OK. If the encoder motor OR the actuator fails to succeed in fully moving when the TCCM commands them to, it will set the light. Most importantly, it permanently gives up trying. You need to reset the TCCM by pulling the fuse to get it to try again.

You could swap actuators with your friend, and/or pull the actuator off the vehicle and see if it whines as expected while it's in mid-air. Putting the skid plate on may have wiggled some wires, even to the encoder motor. Remember my first post - flaky wiring could still be your issue. Compare motor noises to your friend's TB while it sits in the driveway.
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  #7  
Old 02-20-2009, 03:09 PM
Double D Double D is offline
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Why are you shifting to neutral before switching to 4WD? I am not an electronics wizard at all, but with the old vacuum systems this was no no. You just move the switch while driving in gear at any speed. You only need to be driving s-l-o-w-l-y for a switch into 4Lo.
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  #8  
Old 02-20-2009, 03:35 PM
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KHill KHill is offline
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I believe neutral is recommended for the 4Lo switch, everything else is just recommended at 35mph or lower. I can't see this harming anything, although I don't know everything.
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  #9  
Old 02-20-2009, 06:11 PM
Double D Double D is offline
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Per my Owners Manual:

Shifting Into 4HI(Four Wheel Drive) or A4WD(Automatic Four Wheel Drive)
Turn the knob to 4Hi or A4WD. This can be done at any speed unless you are shifting out of 4LO. The indicator light light will flash while shifting. It will remain on when the shift is complete.
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  #10  
Old 02-20-2009, 06:18 PM
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the roadie the roadie is offline
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Going into or out of the LO range requires neutral plus coasting at less than 3 MPH (or stopped). It ensures zero torque on the gear train.
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