4wd won;t engage - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2006 - 2009 TrailBlazer SS Tech > 06-09 SS Engine and Drivetrain > AWD Drivetrain

AWD Drivetrain AWD repairs & problems

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  #1  
Old 01-04-2019, 09:07 PM
TechNova TechNova is offline
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4wd won;t engage

04 Envoy. 90K miles.

when I turn the selector switch to 4wd the light flashes for 10 seconds and then goes back to a solid light for 2wd. I have tried it numerous times stopped and in motion.

I can hear the transfer case motor run, cannot hear the front motor.

I checked the fuse, including using a DVOM, the fuse was good.
I unhooked the front connector, the terminals are in perfect condition.

I checked the voltage and had 12 volts at the brown wire when I had someone turn the switch to 4wd. I had 12 volts for about 10 seconds.

This would indicate a bad front axle selector but a new one did not fix the problem.
I removed the selector, rotated each front tire individually and the front driveshaft did NOT turn. I used a screwdriver to push in on the "fork" in the housing. I could feel the fork move and when I pushed it in, rotating either front wheel caused the front driveshaft to turn.
Does anyone have any other ideas on what could be wrong?
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  #2  
Old 01-04-2019, 11:31 PM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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2004 GMC Envoy SLT
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If you are saying that when a new front actuator was installed, the disconnect still did not engage. In that case there is either a wiring issue ot the TCCM is bad.
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Old 01-05-2019, 09:13 AM
TechNova TechNova is offline
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I am getting 12V for about 10 seconds wen the switch is turned to 4wd.
wouldn't this indicate all is good with the wiring and the module.?
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  #4  
Old 01-05-2019, 10:41 AM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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The brown wire should have 12V on it all the time with ignition on. Have you checked fuse #48 in the rear fuse box? If fuse is good, then you need to determine why the 12V disappears.

The Lt Blue wire is the control for the actuator, but if the 12V supply is not present, the actuator will not function.
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Old 01-05-2019, 10:42 AM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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The brown wire should have 12V on it all the time with ignition on. Have you checked fuse #48 in the rear fuse box? If fuse is good, then you need to determine why the 12V disappears. Maybe what you are measuring is a back feed from another source and the main 12V is not present at all.

The Lt Blue wire is the control for the actuator, but if the 12V supply is not present, the actuator will not function.
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Old 01-05-2019, 02:14 PM
TechNova TechNova is offline
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I checked the fuse, it is good.

I need to recheck the wiring diagram, I had the lt brown as the switched 12V.
AllData doesn't let me expand the diagram very much. I will see if I have it in Mitchell or CCC where I can zoom more.
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Old 01-05-2019, 04:41 PM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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Attached is a diagram of the 4x4 electrics.
Attached Thumbnails
Click image for larger version

Name:	4WD_Schematic.jpg‎
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ID:	37723  
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  #8  
Old 01-05-2019, 04:44 PM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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Previous diagram is not the one I wanted, another attached
Attached Files
File Type: pdf 4x4_System.pdf‎ (145.4 KB, 64 views)
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  #9  
Old 01-09-2019, 07:28 PM
Cjbeckman Cjbeckman is offline
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I believe the flashing is telling you that it can't engage the front axle disconnect. It's mechanical not electrical. That's what happened on mine. There are three rather light weight bearing inside it that when they fail they don't allow the shift collar to slide over the splines. There was a good discussion of it and how to diagnose front axle problems on trailvoy.com but I don't have the link. Sorry
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Old 01-09-2019, 08:31 PM
SteveJL SteveJL is offline
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It doesn't sound mechanical though if pushing the fork in manually engages the axle disconnect- and everything else seems tight? no play in cv/drive shafts/bearings?

maybe getting enough volts- but how about amps? just to try the simplest stuff first... I've had a couple of older cars where slow transmission shifting was one of the the first symptoms of a bad battery/connection
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