ATC fuse blows

LARRY SADLER

MEMBER
2001 CHEVROLET SILVERADO
5.3L
V8
4WD
AUTOMATIC
170,000 MILES

I have replaced fuse, panel switch, actuator, encoder motor and tccm. Still to no avail fuse keeps blowing. Had a shop inspect wires " they said all is good there". I'm at a loss don't think there is anything left to replace or check any advice? Thank you in advance for any help.

7 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Take a look at the wiring diagram. This fuse actually feeds the B+ for the transfer case control module and the encoder motor. I would suggest one of two things. First you can unhook the C2 connector of the transfer case control module and then replace the fuse again and turn the key on and seeing if it blows. Or you can install a smaller fuse on each leg of this wire and then replace the ATC again and see which one blows first. Whichever one does is the leg of the circuit that is the issue. Since this is a 20 amp fuse I would go with a 10 amp fuse on each wire. Point is, we need to limit down the two wires to one so we know which component or wire is the issue.

Let me know if you have questions and we can go from there.

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Friday, February 28th, 2020 AT 4:43 PM

AKPETE17

MEMBER
4 POSTS

So, I’m having a heck of a time trying to figure this out, this schematic and troubleshooting stuff scrambles my brain.

Is there a typo on schematic or in your testing procedure? You reference a C2 terminal, I only see a C1 and C9 on the fuse side of schematic?

Since you’re talking about an immediate fuse blow with key on, does that mean TCCM behind headlight switch is fine?

I put a new transfer case motor, blows ATC fuse like this- With key off, when I put a new fuse in, I hear the T case motor moving then stop. Turn the key on, push button selector indicates 4HI. 20A ATC Fuse stays intact

Press button to 2WD, hear the motor turning, light indicates 2WD; 20A ATC fuse intact.

When I try to cycle back to 4HI, the motor makes noise then the 20A ATC fuse pops.

With a blown fuse I have power to the left terminal (towards front of car)

Any ideas would be greatly appreciated!

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Tuesday, April 4th, 2023 AT 6:39 PM

KEN L

MASTER CERTIFIED MECHANIC
48,389 POSTS

I would remove the transferer case actuator and work the switches, if the motor can be run throughout all modes and is okay the problem is inside the transfer case which is making the motor work too hard and pop the fuse. Please let me know what happens. Also did the fuse condition stay the same with both the new and old actuator motor?

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Wednesday, April 5th, 2023 AT 10:17 AM

AKPETE17

MEMBER
4 POSTS

Thanks Ken, good idea. I hadn’t considered since there’s all sorts of warning stickers on the motor about not operating when not connected.

So, I just got it pulled off and the motor does move without blowing fuse.

I’m now wondering (and hoping) if I had it misaligned- think the motor came factory set in 2WD and maybe my t case wasn’t in 2WD? It did bolt on just fine, not sure how much the selector post moves in between shift positions.

The original fuse state, I’m not sure, didn’t find out about the ATC fuse until after I replaced the t case motor.

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Wednesday, April 5th, 2023 AT 4:55 PM

KEN L

MASTER CERTIFIED MECHANIC
48,389 POSTS

Yep, that could be, here are the instructions for installing the new actuator motor.

Important: When installing the motor encoder unit to the transfer case, make sure that the transfer case is indexed properly and is flat against the transfer case before tightening the mounting bolts.

Check out the images (below). Please let us know what happens.

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Thursday, April 6th, 2023 AT 11:30 AM

AKPETE17

MEMBER
4 POSTS

After many months of driving in 2WD, icy conditions finally pushed me to address this issue.

I actually fully expected it was the t-case, purchased a refurb one and scheduled an install with my very accomplished mechanic friend.

We started to prepare to pull drivelines and he was like your transfer case is engaged!

Which started 12 hours of troubleshooting- ruled out front differential, he ran down all sorts of electrical stuff and got the ground out to the transfer case control module under the dash on the ATC fuse circuit.

As discussed here, the ATC circuit has two power feeds, one to the encoder motor and one to the TCCM under the dash.

Replaced the $330 reman TCCM ($200 core)- and the ATC fuse was still blowing when car was running. Pulled the encoder motor, still blowing ATC fuse. Bought a new encoder motor ($170)

So two electrical components, $500 and 12 hours later it’s shifting in and out of 4WD with no issues

Now to try to sell off a refurbed transfer case!

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Saturday, February 24th, 2024 AT 1:36 PM

KEN L