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Discussion Starter #1
When I push 4x4, the yellow 4x4 light flashes continuosly. No 4x4
I hear the xfercase shift motor when i push the button. Sounds normal
Pulled the plug out of the front actuator... I get 14V at the brown wire all the time wether it's in 4x4 or not. Fuse in the dash side panel is good. Are there any other fuses?

Only wrench in this is a possible wire/connection problem when the truck was repaired. I followed the harness from the actuator all the way up. Everything is connected. I checked the xfer case. Everything is connected. When i disconnected the xfer case plug, the service 4x4 light came on. Figure that was normal. Restart reset the light.

The question is this... what is the most likely problem? Actuator or xfercase switch?
Will the new style actuator I put on my wifes 94 Blazer (Full Size ClassicK) 26060073 fit as a swap test? Looks the same.
Are there other voltage readings I can take at the actuator plug from the other three wires to be sure it's getting the proper signal.

Also... maybe it's not up front at all? I was reading in the si2000 (GM Service CD) that the xfer case looks for the front axle to engage before shifting. Is that true? My si2000 always refers to the Autotrac case. I'm not sure if only the autotrac does that.

I have the option of taking it in to the dealer. I have extended warranty. Just like fixing things myself and not having to come up with something to drive while it's there.
Edited by: hoot
 

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Discussion Starter #2
Got my answer....


If you can hear the encoder motor on the tcase moving it does sound like the front axle is not engaging, but that would only be a guess. The first step is to see what, if any, code set. But if you want to check the actuator here’s how it works, power is supplied from the 4wd fuse on the brown wire, it should have 12v all the time (key on)and should be checked with a test light. The TCCM grounds the lt. blue wire to turn on the actuator. When the axle has engaged 12v is sent from the actuator to the TCCM on the black/white wire, this tells the TCCM the axle has engaged. You can check the power and ground but putting your test light on the solid black wire (pin E) and probing the brown wire (pin C). You will need a Tech 2 to command the circuits on and off to do other checks. G110 ground is located on the L/F body mount, right below the driver’s door on the frame.



If the TCCM doesn’t see that the axle has engaged it will cancel the shift.

Also, if you take to the dealer, let them know you unplugged the connector or they might try chasing the codes it set.


Thanks GMSID and dmaxalliTech for responding (via email)
 

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Discussion Starter #4
Be doing some checking tonight. No 4x4 yet.
 

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Discussion Starter #5
Bingo!

The short harness from the actuator to the plug attached to the drivers side wheel well liner apparently was pinched when the tree slammed the truck.

No continuity in the black wire through that harness.

GMSID... you da man
 

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Good job, Hoot! You saved yourself a trip to the dealer, although you probably might have got a lot of new parts thrown at it before they found the short.
 

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Discussion Starter #7
poolrebel stopped over and helped out checking one end to the other. We disconnected the C150 plug and checked the harness from the connector-to-frame wire (G110). Had ground there. That was a good sign.

From the connector to the actuator we got nothin.

The GM troubleshooting steps also were excellent in this case along with your instructions GMCSID.

Thanks again.
 

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Discussion Starter #8
 

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i have seen time and time again the 4x4 sw shorted and causing an intermittent 4x4 service lamp on. 9 times out of 10 the 4x4 sw is at falt. again as a tech i have seen thousands of these why no recall. its a known problem and has a bulliten. the switch is about $45 dallars to replaced it remove the cluster trim by pulling straight out tilt the wheel and shif the shifter to 1 to ease removal with a small screw driver release the tab holding the switch remove harness conector replace
 

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Discussion Starter #11
patrick said:
i have seen time and time again the 4x4 sw shorted and causing an intermittent 4x4 service lamp on. 9 times out of 10 the 4x4 sw is at falt. again as a tech i have seen thousands of these why no recall. its a known problem and has a bulliten. the switch is about $45 dallars to replaced it remove the cluster trim by pulling straight out tilt the wheel and shif the shifter to 1 to ease removal with a small screw driver release the tab holding the switch remove harness conector replace
My buddy poolrebel just had his replaced for the same reason.... then we replaced the NSBU switch last week.
 

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I get the new switch put in on friday. Dealer had to order it and it arriver today. Luckly they are going to cover it under warrent.
 

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Discussion Starter #13
Thought you had it done Jay.

Interested in a couple of bags of sand? I picked up a few too many sand tubes for ballast. You can have them. 60lbs each. Got two extra.
 
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