4WD service light on, 4WD works, possible C0379 code - 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 08-21-2011, 01:21 AM
blurry blurry is offline
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2002 Chevy TrailBlazer LT
Sand Beige Metallic 4.2L I6 4X4
Join Date: Nov 2008
Location: liverpool, ny (north of syracuse)
Posts: 39
4WD service light on, 4WD works, possible C0379 code

In my spare time I've been chasing the 4WD service in the wife's 02 trailblazer. I'm set on pulling this code myself without a tech2 and am making some progress (http://forums.trailvoy.com/showthread.php?t=90204)

I'm pretty sure I'm seeing a C0379 front axle actuator code.

here's the story:

turn the 4WD switch to 4WD:
* can hear the encoder motor and the front axle actuator.
* 4WD light keeps blinking
* service light comes on
* driving the truck 4WD and 4LO seem to work (all while the light is flashing)

replaced axle actuator from junk yard, same issue
removed actuator and ran outside of truck, same issue
took one of the axle actuators and there was grease on the connectors, cleaned and now it doesn't work anymore (no biggie)
checked connector and actuator, pins look good
checked wiring going into the main bundle, no sign of damage
replaced TCCM with a spare, same issue

what's next? I tried to read the signals on the actuator, but I'm not sure what to look for. the outer two lines seem to be power and the inner possibly command and signal - anyone know which color wire does what?

thanks for the help!
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  #2  
Old 08-21-2011, 05:15 PM
the roadie's Avatar
the roadie the roadie is offline
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2004 GMC Envoy SLT "Roadiemobile"
Extreme Offroad Pewter 4.2L I6 4X4
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I thought I knew all there was about this system - you've got a unique problem. I'd suspect the TCCM except you swapped it. Was your spare also one of the suspect early 2002 units?

Anyway, the front axle actuator:

Pin A light blue control (5V/ground for in/out and I believe but it might be 12V and ground)
Pin B black ground
Pin C black/white stripe sensor feedback (low for one way -I forget which - in or out, high (5V?) for the other way.
Pin D brown power
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  #3  
Old 08-21-2011, 07:35 PM
blurry blurry is offline
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2002 Chevy TrailBlazer LT
Sand Beige Metallic 4.2L I6 4X4
Join Date: Nov 2008
Location: liverpool, ny (north of syracuse)
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check the sensor feedback and it goes to 12V when engaged (11V actually, but whos counting!)

I pulled all the wires from the protective sleeve and no visible damage to where it joins with a larger bundle on the other side of the engine.

any more ideas?
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  #4  
Old 08-22-2011, 12:08 AM
blurry blurry is offline
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2002 Chevy TrailBlazer LT
Sand Beige Metallic 4.2L I6 4X4
Join Date: Nov 2008
Location: liverpool, ny (north of syracuse)
Posts: 39
Quote:
Originally Posted by the roadie View Post
I thought I knew all there was about this system - you've got a unique problem. I'd suspect the TCCM except you swapped it. Was your spare also one of the suspect early 2002 units?

Anyway, the front axle actuator:

Pin A light blue control (5V/ground for in/out and I believe but it might be 12V and ground)
Pin B black ground
Pin C black/white stripe sensor feedback (low for one way -I forget which - in or out, high (5V?) for the other way.
Pin D brown power
Just realized I never answered your question- one of the tccm units is an 08 the dealer put in a few years ago new, and the junk yard one is an 03. The 08 unit is in right now.

Thanks for the help
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  #5  
Old 08-22-2011, 09:34 PM
blurry blurry is offline
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2002 Chevy TrailBlazer LT
Sand Beige Metallic 4.2L I6 4X4
Join Date: Nov 2008
Location: liverpool, ny (north of syracuse)
Posts: 39
Does the status line for the actuator go through the connector on the side of the fuse box? there are two black with white stripe, the smaller gauge looks like a match. I'm thinking of testing the signal along the way to the TCCM to see where the signal is lost.

here is a picture (the connector on the side is where I suspect the wire passes through:

NOTE: I found the picture on-line, our truck doesn't have the extra wire!



based on this wiring diagram (E11 and D6 on the "CONN ID" connector):

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  #6  
Old 08-25-2011, 08:45 PM
blurry blurry is offline
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2002 Chevy TrailBlazer LT
Sand Beige Metallic 4.2L I6 4X4
Join Date: Nov 2008
Location: liverpool, ny (north of syracuse)
Posts: 39
I'm not getting voltage at C2-B6 on the TCCM, however the actuator reads voltage on the black/white wire. I'm going to cut the wire after the connector and check it. if that has voltage (not a connector issue) then I'm running a new wire to C2-B6.

hopefully that will keep the service light off
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  #7  
Old 08-26-2011, 10:08 PM
blurry blurry is offline
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2002 Chevy TrailBlazer LT
Sand Beige Metallic 4.2L I6 4X4
Join Date: Nov 2008
Location: liverpool, ny (north of syracuse)
Posts: 39
That fixed it! after testing I ran the wire in the original housingand ended up finding the damaged wire. It was pulled out of the housing and crushed - funny thing is that I can't figure what damaged the wire.

For anyone with similar issues: if you are getting the actuator code (C0379), test the voltage between the ground C1-B8 (connector to the outside of the TCCM with a lot of wires) against C2-B6 (center connector on TCCM). if it doesn't read 12V then check between the two center cables on the axle actuator. if those are 12V there is a wire issue - if that is not 12V the actuator sides internally might not be working (grease?)
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