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Old 01-14-2009, 09:39 AM   #1
loulblades
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Default 4 Wheel Drive Diagnostics


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I ran across this troubleshooting guide for 4 wheel drive from another source. I cleaned it up a bit and reformatted it some. It is in a Microsoft Word format
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File Type: doc Chevy 4WD Diags.doc (469.0 KB, 533 views)
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Old 01-23-2009, 09:17 AM   #2
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interesting, i did not know you could determine DTC (diagnostic trouble codes) without an OBD II scanner. that file provides instructions on how to make the 4x4 buttons blink in a "Morse Code" like fashion to reveal any trouble codes concerning the 4x4 system. very cool!

haven't tried it, but if it's accurate that is a great find.
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Old 02-03-2009, 10:11 AM   #3
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i can't get the word document to open,is there another link around with this info?
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Old 12-05-2009, 04:14 PM   #4
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Default diagnostics codes

loulblades,
I've went through your word document and it looks very promising for troubleshooting the electric version of tahoes 4x4. As for my self i consider my self to be some what knowledable about cars and electricity. So I'm coming to you for your opinion on a matter of my 4x4 recently my 4x4 has gone out the 4hi and 4lo blink constantly when i try to engage it. i can hear the soleniod engage but i can tell its not in 4wheel drive. so i put it on a lift then engaged the 4hi and again i can hear the soleniod engage on the transfer case plus the front driveshaft also starts to spin but of course the wheels are doing nothing. So i took it a step further and checked to see if there was voltage at the front diff soleniod and yes there was so i assumed it was the soleniod gone bad. Then i go to a local junkyard and replace it with another one and what happens the same thing. But i do notice when i manually engage the front diff the 4hi indicator light stays on and the front wheels spin and switch does not blink making me think that the other electical plug on the front diff is the indicator for the switch on the dash. So do i just have bad luck and grabbed a bad front soleniod from a junkyard that cost me 5 bucks or is there something else i'm missing. When i tested the other soleniod i did not install it first time instead plugged it in then had the 4hi button pushed i wanted to see if i can see the plunger stick out or not, i also tried it in the axle as well.. fuses were also checked and came out good with power running through them..

Your help on this matter is greatly appreciated.
R.Flores
Sgt./USMC
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Old 12-05-2009, 08:55 PM   #5
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Since you said the light quit blinking when you manually engaged the front diff that let's you know that the fedback to the TCCM is good.

Also since you said there was another connecter on the diff, I am figuring this is the thermal solenoid type. There is a TSB to convert from the thermal to motor type. With the motor type the proximity sensor (second connector) is not used.

The thermal type are very prone to problems. If it is cold out they take longer to engage and sometimes don't. It wouldn't surprise my at all to pick one up in the junkyard that didn't work. They can be tested by applying 12 volts to it (again the thermal variety). The motor type is a little more complex.

Of course I said all this without knowing the year of your truck. Pre January 96 Tahoes had the thermal types as far as I know unless they were converted.

Hope this helps.
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Old 12-06-2009, 01:11 AM   #6
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Default thermal

Ah yes just a couple of things i forgot to mention that you reminded me on your post.
Well first of all My TAHOE is a 97 second of all i thought about that not knowing if it was thremal or not i went ahead and tried warming up the soleniod but still nothing. you stated something about a different type actuator the motor type HMM might be something i want to look into. I'm trying to get all the lil bugs and stuff out the truck before i deploy next year so that way it doesn't worry my wife . thanks again..
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Old 12-06-2009, 01:48 AM   #7
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Default tsb

ahh i think i found what your talking about
http://www.4x4posi-lok.com/app_chevy-k.html

that is a simple and almso fail safe way of doing it right there
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Old 12-06-2009, 10:34 AM   #8
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This is not what I was referring to. The Posi-Lok is used to get rid of the actuator and manually engage the front diff.

The motor type actuator requires 12 volts all the time (when ignition is on). 12 volts is applied to cause the actuator to engage and the other pin on the connector is the feedback to the TCCM (transfer case control module) to let it know the diff is engaged.

If you put the Posi-Lok in, you don't have to worry about actuators any more.
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Old 12-07-2009, 12:37 AM   #9
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Default 12vdc actuator ??

Oh ok well in that case i need a lil help in guiding me to the right direction on that one. Last night i really couldn't sleep so i had found that posi-lok actuator for $179-202 but the more i was looking into it and at it I was thinking well if i can find an 12vdc actuator that can push that pin in then i'll fabricate a bracket and some sort of rubber gromet to stuff inside the hole where the soleniod was. Anyways i really didn't find anything but if you got something a pic or website then please shoot it my way so that way i can look more into it.
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Old 12-07-2009, 10:53 AM   #10
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Look above the actuator on the diff to see if there is a 2 pin connector. This is what is used on the thermal actuator type to determine if the diff is actually engaged or not.

I think that since your truck is a 97 it should have the motor type actuator. I believe that 96 was the last year that the thermal actuator was used on 1/2 ton trucks but I can't state that as a fact, someone else may know.

The actuator is available at an auto parts for less than $100.
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