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Virtual Wrench (L J)
Virtual Wrench (L J), Chevy Mechanic
Category: Chevy
Satisfied Customers: 13357
Experience:  35 years Master Mechanic
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Chevrolet S10 Blazer 4x4 (Mid Size) I have a 2001 Chevrolet

Customer Question

I have a 2001 Chevrolet Blazer LT 4WD with 4 button 4WD switch. The ATC fuse keeps blowing. My VDR shows a DTC - C0323. I have changed the following in an attempt to correct the situation:

1. Replaced the TCCM.
2. Replaced the Encoder Motor (Doorman) Don't know if that was a good idea!
3. Replaced the Switch on the front differential.
4. Replaced the Vacuum valve under the hood.

C0323 usually is the Encoder Motor not locking. Could I have a bad aftermarket encoder? Should I acquire the GM Part# XXXXX actuator-encoder motor and return the other?
Submitted: 3 years ago.
Category: Chevy
Expert:  Virtual Wrench (L J) replied 3 years ago.

Hello,

 

If you tell me the fuse number i can look up that circuit and see what all is controlled from it. Check all of the fuses also, they all tie into the 4x4 circuit

 

graphic

 

Customer: replied 3 years ago.

Hello,

 

I really don't know what you mean by the fuse number. It is in the fuse box under the hood. I believe it would be the E5. It is 20A. None of the fuses in the box inside are blown.

Expert:  Virtual Wrench (L J) replied 3 years ago.

Thanks, XXXXX XXXXX appear to be the right one,

 

Lets try the procedure below to see if we can pull any codes from the TCCM,,,it will be different than the C0323 code. If you can do that and get back to me, we will go from there.

 

graphicgraphic

Customer: replied 3 years ago.

This might be a silly question, but which pin is pin 13? Can you supply a pic?

 

Thanks

Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi,

 

Nothing wrong with asking that :-) jumper #16 to a good ground.

 

graphic

Customer: replied 3 years ago.

Thanks. It will be awhile before I get back to you this time. Hope that is OK. What is your name so I get the same person OR can wait for the same person.

 

Thanks,

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi Joe,

 

That is just fine, just reply right back here to this page and let me know. We can work as long as is needed and I will be around all day. You might just bookmark this page to get back easier.

 

LJ

 

 

Customer: replied 3 years ago.

LJ,

 

Nothing, just kept blowing the Diag fuse. Tried with the ATC blown and the a new ATC.

Nothing at all. No blinking of any kind.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi,

 

Got a problem child here 'eh.....If you click here you will get the wiring diagram for the 4x4 system. What you are going to have to do is start by disconnecting things to isolate which circuit that is causing that fuse to blow. You have replaced just about everything is the system other than the shift control switch and the PCM. and wiring that may be shorted to ground somewhere. It's just going to take some pretty involved testing along with a pocket full of fuses to find it. The possibilities are just so many that it is hard for me to tell from here. Give it a go with that diagram and let me know how it goes.

 

 

Customer: replied 3 years ago.
One more question. Will TCCM GM# XXXXX and 12577412 interchange? They are both for the NP8 transfer case, and supposed to be for the S10, Jimmy, Blazer, Bravada, Astro My vin is: 1GNDT13W012110915.
Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi,

 

I don't know with 100% certainty they will interchange, but i do know the 12577412 fits the 2001 Blazer you have.....not sure if that helps any...

 

graphic

 

 

Customer: replied 3 years ago.

Perhaps this could be the problem. Need a good way of cleaning the contacts:

 

graphic

Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi there,

 

Yep,,,i think you are onto something now..

 

Maybe use some spray electrical contact cleaner on the connections and try to get them to secure real good. I would also make sure to check the other ends of those wires for signs of corrosion as well. Thanks for the update and keep me posted if needed. I will be on here tomorrow too.

Customer: replied 3 years ago.
Before you go. The shorting out would not blow the TCCM would it?
Expert:  Virtual Wrench (L J) replied 3 years ago.

Sorry, just missed you.

 

Well,i hate to say it but,it is always a possibility. Just make sure those contacts on the connection don't let the wires touch together, like to the ground wire. then connect it back up and see what happens. Talk tomarrow.

Customer: replied 3 years ago.

LJ,

 

Have to wait on parts, then try everything. I'll get back to you in a couple of days or so. Not trying to put you off or anything.

 

Thanks,

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

No problem Joe,

 

Just give me a shout when you want.

Expert:  Virtual Wrench (L J) replied 3 years ago.

Hello Joe,

 

Just checking on how things are going and i didn't want our conversation to time out. Let me know when you can please.

 

 

Customer: replied 3 years ago.

LJ,

 

Still waiting on parts.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Thanks Joe,

 

i will check in with you next week if i haven't heard from you, just so your question doesn't time out.

 

Thanks

 

 

Customer: replied 3 years ago.

LJ,

 

Thanks so much for your patience. Just don't want to have to spend another $48 to get you back...if you know what I mean.

 

Thanks,

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Yeppers i sure do!

 

You might want to just bookmark this page for easier return.

 

Talk later.

 

 

LJ

Customer: replied 3 years ago.

LJ,

 

Parts are here. Should be done by Sunday.

 

Talk to you then.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Thanks for the update.

 

Good luck Joe.

 

 

Customer: replied 3 years ago.

LJ,

 

Took out the aftermarket encoder and replaced with GM. Replaced the cable to the front axle. The vacuum hose connects to the top on the vacuum guage, correct?

 

Well, anyway, worked four or five times and blew the fuse! "Everything" is new, Genuine GM parts now.

 

Cleaned the heck out of the plug for the TCCM.

 

Don't know where to go now.

 

Joe

Customer: replied 3 years ago.

LJ,

 

Up above I meant the vacuum switch under the hood by the firewall. Should I have a short to ground, where would be the most likely place to find it?

 

Thanks,

 

Joe

Customer: replied 3 years ago.

LJ,

 

The only two places it could possibly be the TCCM or the Encoder Motor. The ATC fuse supplies power to thos two units. Figuring which one is the problem.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi Joe,

 

If you disconnect the shift cable, see if it still blows a fuse. It wont engage the front axle, but you can tell if shift fork may be binding inside, causing that fuse to blow.

 

graphic

 

 

 

 

Customer: replied 3 years ago.

LJ,

 

Try that tomorrow.

 

Will let you know.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Ok,

 

If it doesn't blow you know the area of the problem, but If it still blows, then you just leave it disconnected and disconnect the switch on that shift fork assembly Part # XXXXX in that last diagram i sent and see if it blows,,,let me know tomorrow or whenever you get a chance.

Customer: replied 3 years ago.
Do I switch it through the gears anyway? 4LO never works because the transfer case is to old I guess.
Expert:  Virtual Wrench (L J) replied 3 years ago.

Yes you can....i didn't like to hear the 4 low not working though :-(

Customer: replied 3 years ago.
Well, the 4LO has never worked since I have owned it. It goes in but never comes out and then another encoder and manually taking it out of low. Maybe the transfercase?!?
Customer: replied 3 years ago.

Can you give me the part number for the transfer case? Vin: 1GNDT13W012110915

Customer: replied 3 years ago.

NP8 automatic transfer case, two speed automatic.

Expert:  Virtual Wrench (L J) replied 3 years ago.

Sorry, had to step out,

 

Here you are.

 

GM # XXXXX

 

Also click here for the description and operation of the 236-NP8 as you will see it's a pretty involved system.

Customer: replied 3 years ago.
Any reason why it won't go into 4LO?
Expert:  Virtual Wrench (L J) replied 3 years ago.

Good morning Joe,

 

In most all cases it is because of binding inside of the T-case and would have to be taken apart to find out exactly why. This will also blow that ATC fuse you have come to know so well :-)

 

I also spoke to a friend of mine who works at GM and is pretty darn familiar with the 4x4 systems on these and here is what he had to add.

 

I have seen many harness problems at the pinch weld above the transmission where the harness runs down to the encoder. It is very hard to see in the truck, so you have to disconnect the harness and pull it up from the top to see if it is chaffed and shorting to ground in this area. I have had to rerun the wires from the TCCM to the encoder motor A/B circuits, and from the underhood fuse box, using 14 gauge wire,to correct issues of blowing this fuse and use a 25 amp fuse , instead of the 20 amp. There has to be a short to ground, or binding in the transfer case, to blow the ATC fuse. I think the problem is in the transfer case,( since it has problems getting it in and out of 4 low), and/or the harness shorted. Definitley go for the wire issue before you go replacing the T-case.

 

LJ

 

Customer: replied 3 years ago.

I will check it out.

 

Thanks LJ

Expert:  Virtual Wrench (L J) replied 3 years ago.

You are most welcome.

 

Please don't forget about me :-)

 

LJ

Customer: replied 3 years ago.
I won't. We can end this if we can exchange email, and go from there. Mine is XXXXX@XXXXXX.XXX
Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi Joe,

 

I wish i could, but we are not permitted to work with customers off the site :-( if you notice your email addy gets X'ed out so it's not even possible.

 

HOWEVER, if you please click on accept for my time spent already to show your appreciation, we can still communicate right here on this page as long as you like with absolutely NO extra charge at all.

 

LJ

Virtual Wrench (L J), Chevy Mechanic
Category: Chevy
Satisfied Customers: 13357
Experience: 35 years Master Mechanic
Virtual Wrench (L J) and 5 other Chevy Specialists are ready to help you
Customer: replied 3 years ago.

LJ,

 

Accepted. Glad we can still finish this.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Thanks Joe.

 

Just reply back right here if needed.

 

LJ

Customer: replied 3 years ago.

LJ,

 

Found a transfer case with 55K miles for $309. Got to get that one...never find one like this again! Anyway, it will be easier to check the wiring with it out anyway.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Wow! That is a great price.

 

And yes, it sure will open up that area much better.

 

Best wishes my friend!

Customer: replied 3 years ago.

LJ,

 

Got it to go into 4LO, but the with a very loud clunk and jerk. Came out of 4LO ok.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.
Yup, sounds like it's been binding.
Customer: replied 3 years ago.
Transfercase or front axle? Sounded like the transfercase.
Expert:  Virtual Wrench (L J) replied 3 years ago.

Most likely the t-case.

Customer: replied 3 years ago.

LJ,

 

Transfer case in, shifts well through all gears. Have started it several times without blowing the fuse. Haven't driven it yet...keep your fingers crossed the fuse doesn't blow when I do. I will let you know.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Good morning Joe,

 

Got 'em crossed for you!

 

Let me know how it turns out please.

 

 

Customer: replied 3 years ago.

LJ,

 

Took it for a short drive, shut it off, started it again...fuse not blown! So, that was the initial test. Tomorrow, I take it for a 110 mile trip. If the fuse does not blow tomorrow, I think we are safe.

 

Thanks for all your help. Let you know how it goes tomorrow.

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Sounds good,

 

Don't wear it out now...:-)

 

LJ

Customer: replied 3 years ago.

LJ

 

Houston, we have ignition. Fuse has not blown...don't think it will now.

 

Thanks much for your help.

 

Joe

Customer: replied 3 years ago.

LJ,

 

How do I print this conversation?

 

Thanks,

 

Joe

Expert:  Virtual Wrench (L J) replied 3 years ago.

Hi Joe,

 

Thanks for the update. Other than just copy and paste, i don't know how else you would print everything.

 

Glad you got it handled.

 

 

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