Np 246 pinout?

[xDan]

Hey does anyone have the encoder motor pinout for the 246? 2003 if year matters. My tccm doesn't throw codes, the pushbutton control responds to shift requests, which is also evident on the tech 2 data page. Shees stuck in 4hi, and the only mode it goes to is 4wd auto, but the SUV always starts in 4hi. Really need a pinout... The only ones I'm finding are exploder or 243.

 

[Fless]

Try this, but I think this gen has a 5v reference (at least at the switch):

Full article here: https://atracom.blob.core.windows.net/gears/2006/2006-08/2006_08_08.pdf

 

[Fless]

That sounds like a bad encoder motor. On mine it would start in 2hi, I could switch it into 4x4 and the mode light would indicate that, but the Tech 2 showed actual was Auto. If you get to the decision that it's the motor, you can replace the resistance ring inside, or get a whole new motor. Pretty sure @Sam Harris and some others have done the fix instead of the full replacement.

 

[Sam Harris]

That sounds like a bad encoder motor. On mine it would start in 2hi, I could switch it into 4x4 and the mode light would indicate that, but the Tech 2 showed actual was Auto. If you get to the decision that it's the motor, you can replace the resistance ring inside, or get a whole new motor. Pretty sure @Sam Harris and some others have done the fix instead of the full replacement.

Yup. Mine was acting strange for a couple years. It would randomly show the incorrect mode, even though it was in the expected 2wd mode. It also reported “SERVICE 4WD” fairly regularly, though a stop / start would typically clear that up. Sometimes she would refuse to go into the requested t-case mode, like 4hi, or auto.
Once I started her up and it showed in 4lo, and I couldn’t get it to change, I decided it was time to look into it further (again it was truly in 2wd, thankfully), so I was still able to drive fine. I changed the encoder ring, p/n: 88962315, after my Tech2 confirmed it was the problem. No trouble whatsoever since.. cheap replacement part, and the swap was easy.

It’s buried somewhere in the what did you do to your GMT800 thread. I suppose I really should have a build thread. It would make this kind of reference a lot easier.

 

[Fless]

@TJ Baker has a post with pics:

Service 4wd issue

Before anyone asks, yes I search the forum but didn’t find anything quite like I’m experiencing. Any and all help is appreciated. 1998 Tahoe with push button 4wd with auto mode. When I turn on the vehicle no warning light comes on. After I drive for about 5 to 10 min the service 4wd light comes...

www.tahoeyukonforum.com

 

[xDan]

Hmm, some colors are sure to match up, or that is at the TCCM? At the encoder motor on the tcase, it's an 8 pin connector utilizing 7 pins. RED, ORANGE, TAN and BLACK are 12 or 14 gauge, with a dark blue/white, brown/white and green/black 20 gauge wires. The connector pins and wires coming off the backshell are all good, with the right amount of dielectric grease in there. So the grn/blk is the reference voltage, and when disconnecting that plug and starting it up, probing that gives 3.95V and it drops off to low after 4WD codes trigger...I tried testing as per the 2002 and older method with it disconnected but I wasn't getting good voltage drops on anything really...maybe the TCCM is dropping it's signals when that is disconnected?

Anyways, I went into it further with the tech 2 and noticed the following:
Pulling the TREC CB and resetting the TCCM triggers three ATC codes:
C0306 - Motor A/B circuit malfunction
C0321 - Tcase lock circuit malf.
C0327 - Encoder circuit malf.
After erasing the codes, if it's in park, no 4WD codes trigger but in neutral, C0327 returns.

On the data screen I'm getting:
Encoder supply: 5.09V, and that holds steady ALWAYS
Encoder return: 4.08V, varies a little but good and stuck at the 4hi voltage, even during switch commands...so the encoder motor seems to be reporting the correct gear back to the TCCM (and it's definitely stuck in 4hi, I can hear the front driveshaft engaged as well as the front half shafts.
Mode switch return: 0.51V and during switch command delays or motor calls, that voltage stays constant. I'm unsure what this means, if that is normal or what?

In 4hi, it shows tcase lock disabled and when switched to auto 4wd, shows tcase lock enabled. Both modes show front axle requested as YES.

When going into the tcase function menu, all lights and button selections work, transfer case lock mode works.
When ATC motor A or B control is activated, I get this error: "Motor control attempted within 10 sec of previous control" no matter how long I wait. The tech 2 displays -50% motor load when turning ON either circuit, and -5% when selecting OFF.
Of note: When I trigger motor control, I can faintly hear the motor turning, with no grinding noise or clunks, until the error message displays.
I also, of course, inspected the two output shafts for play, leakage and damage but they are just fine. I also checked the fluid and it's a nice blue color at the fill hole. No sign of leakage anywhere on the tcase or trans either, just the engine rear main seal leak.

It's probably something in the encoder has gone bad IMO, as you all are saying, but with hearing the motor rotate and getting that error, could it possibly be the motor shaft is sheared off somewhere? It's too dark to pull the driveshaft and remove that encoder, I'll have to do it tomorrow. Let me know if after seeing all this info, if that just reaffirms the encoder motor or possibly something else? I wish this thing was a 241 or better yet, a 205! lol.

 

[Sam Harris]

I’d still expect it’s the encoder ring. Besides, it’s a cheap, fairly easy replacement. Be sure to let us know the result, either way. Keep us updated. And good luck.

 

[Fless]

I’d still expect it’s the encoder ring. Besides, it’s a cheap, fairly easy replacement. Be sure to let us know the result, either way. Keep us updated. And good luck.

I tend to agree with this, since you're getting the lock circuit and motor codes for one. If you replace the entire encoder motor assembly, save the old one for a ring replacement. Wouldn't hurt to have a spare if that's all that's wrong with it. The encoder motor as a unit is the weak link.

It's curious, though, that the Auto setting is commanding the front diff actuator. I'm not sure that it should do that until the TCCM tells it to engage, and for that you need wheel speed differences. But I'm not sure, and I'll have to check into that next time I have the Tech 2 plugged in to mine. One thing you could do is remove the front diff actuator and see if it's engaging during both (actual, per the Tech 2) Auto and 4x4 modes. In Auto it absolutely shouldn't engage until the TCCM senses speed differences between the front and rear wheels.

It also wouldn't hurt to see if there are updated calibrations for the TCCM, although typically that module isn't the problem with this setup. For that you'd need TIS2000 to use with your Tech 2, or using the newer online check.

 

[Fless]

One thing to add is that the diagrams in the link I posted don't necessarily apply to our pinouts, as you have correctly noted the 8-pin connector at the encoder motor. I have yet to find a wiring diagram that is for the 2003-2006 version of the encoder motor connector. AlldataDIY probably has it.

 

[exp500]

Maybe these will help-

 

[exp500]

Maybe these will help-

 

[Fless]

Maybe these will help-
View attachment 356308View attachment 356309

That shows the 8v system to the dash (select) switch. Mine is 5v reference from the ATCM (TCCM) on F14 (and F13 to the encoder motor). Seems to be for the earlier models; not sure how much different the newer systems would be.

 

[xDan]

That shows the 8v system to the dash (select) switch. Mine is 5v reference from the ATCM (TCCM) on F14 (and F13 to the encoder motor). Seems to be for the earlier models; not sure how much different the newer systems would be.

Yea. The 2003-2006 is unique, but mostly similar to the previous iteration, in functionality. NBS is 5V ref. and has motor A/B simplified control vs the older system. I'm ordering an encoder motor assembly...if that fixes it, I may tear down my old one to maybe figure out the differences.

 

[Fless]

Yea. The 2003-2006 is unique, but mostly similar to the previous iteration, in functionality. NBS is 5V ref. and has motor A/B simplified control vs the older system. I'm ordering an encoder motor assembly...if that fixes it, I may tear down my old one to maybe figure out the differences.

Have you had your encoder motor off? If so, does the shift shaft on the T/C have two flats, or is it splined?

 

[xDan]

It's curious, though, that the Auto setting is commanding the front diff actuator. I'm not sure that it should do that until the TCCM tells it to engage, and for that you need wheel speed differences. But I'm not sure, and I'll have to check into that next time I have the Tech 2 plugged in to mine. One thing you could do is remove the front diff actuator and see if it's engaging during both (actual, per the Tech 2) Auto and 4x4 modes. In Auto it absolutely shouldn't engage until the TCCM senses speed differences between the front and rear wheels.

I found a good writeup on the avalanche forums, the motor lock circuit, when de-energized (disabled in tech 2) actually LOCKS the encoder motor in it's current gear selection. When showing ENABLED in the tech 2, that energizes the circuit and the lock is turned OFF. Only during gear change commands and in auto 4wd (during an adaptive mode) is the lock circuit enabled (turning OFF the lock)...so it should only enable when actively changing the clutch fork on the clutch, like you said. It is counterintuitive. This is a DC motor electronic lock within the encoder motor control circuitry, not anywhere else, only commanded by the TCCM.

 

[exp500]

I never found a service manual for 2003-2006 that showed a different wiring diagram.
Then also this S/B-
GM SERVICE BULLETIN
Bulletin No.: 05-04-21-003C
Date: April 15, 2008

Subject:
Service 4WD Light Illuminated, DTC C0374 Set (Inspect Wiring Harness to Transfer Case Speed Sensors,, Replace Wiring Harness) Models:
2004-2007 Buick Rainier
2003-2006 Chevrolet Avalanche, Suburban, Tahoe
2003-2007 Chevrolet Silverado Classic, TrailBlazer, TrailBlazer EXT
2003-2006 GMC Yukon, Yukon XL
2003-2007 GMC Envoy, Envoy XL, Sierra Classic
2003-2004 Oldsmobile Bravada
2005-2007 Saab 9-7X With Four Wheel Drive or All-Wheel Drive

and Active All-Wheel Drive (RPO NP4) or Active Two-Speed (RPO NP8) Transfer Case

Supercede:
This bulletin is being revised to update the Model and Warranty Information. Please discard Corporate Bulletin Number 05-04-21-003B (Section 04 - Driveline/Axle).

CONDITION:
Some customers may comment on intermittent illumination of the Service 4WD light. Upon investigation, the technician may find DTC C0374 set. The customer may also comment on intermittent erratic operation of the 4WD or AWD system after driving through rain/snow or simply going through a car wash.

CAUSE:
The speed sensor signal may have become corrupted. Possible openings in the speed sensor wire insulation (twisted pairs) can allow water intrusion. Also wire connections contaminated by water may result in short circuits and erroneous speed sensor readings. This most often occurs on the rear speed sensor circuit.

CORRECTION:
Inspect the wiring harness to the transfer case speed sensors. On Rainier, TrailBlazer, Envoy and 9-7X models, fabricate a replacement speed sensor harness between the C101 connector and the speed sensors. Completely inspect and test all wiring. Refer to Speed Signal Front Axle Actuator and Indicators schematic in SI.

Replace the affected twisted pairs. Do not over-twist the two wires in the replacement harness. Wires should be twisted at a rate of 9 revolutions per foot. Use service connector pack, P/N 88987993 at the speed sensor end and terminal, P/N 15326267, at C101.

Terminal testing tools and service terminals can be found in Terminal Repair Kit J 38125. Terminals are available from SPX/Kent-Moore.

The smaller transfer case harness splices into the larger chassis harness a few inches in front of the cross-member. The chassis harness routes along the left side of the frame under the driver door area. Use nylon tie straps to secure the fabricated harness to the main chassis harness between the transfer case and C101.

On the full-size pickup and full-size utility models, replace the 2.2 m (88 in) pigtail harness that runs from the C151 connector under the hood to the transfer case. Use either harness P/N 15832722 or 15224663 depending on vehicle equipment. Refer to Propshaft Speed Sensors Front Axle Actuator and Transfer Case Shift Control Switch schematic in SI.

Important: Technicians should verify the integrity of the splice joints after the repair. All splice joints and connections should seal properly against water or a repeat condition can occur.

 

[Fless]

I actually knew that about the encoder motor. Kind of works reverse of what you'd think, until it's explained.

I was talking about the actuator on the front diff -- it's commanded on in 4HI and 4LO, engaging the front diff fulltime. But it should be commanded off in AUTO, until the TCCM's speed sensors' input tells it to engage. That's the AUTO part of the mode, engaging/disengaging only the front diff.

 

[xDan]

I never found a service manual for 2003-2006 that showed a different wiring diagram.
Then also this S/B-
GM SERVICE BULLETIN
Bulletin No.: 05-04-21-003C
Date: April 15, 2008

Subject:
Service 4WD Light Illuminated, DTC C0374 Set (Inspect Wiring Harness to Transfer Case Speed Sensors,, Replace Wiring Harness) Models:
2004-2007 Buick Rainier
2003-2006 Chevrolet Avalanche, Suburban, Tahoe
2003-2007 Chevrolet Silverado Classic, TrailBlazer, TrailBlazer EXT
2003-2006 GMC Yukon, Yukon XL
2003-2007 GMC Envoy, Envoy XL, Sierra Classic
2003-2004 Oldsmobile Bravada
2005-2007 Saab 9-7X With Four Wheel Drive or All-Wheel Drive

and Active All-Wheel Drive (RPO NP4) or Active Two-Speed (RPO NP8) Transfer Case

Supercede:
This bulletin is being revised to update the Model and Warranty Information. Please discard Corporate Bulletin Number 05-04-21-003B (Section 04 - Driveline/Axle).

CONDITION:
Some customers may comment on intermittent illumination of the Service 4WD light. Upon investigation, the technician may find DTC C0374 set. The customer may also comment on intermittent erratic operation of the 4WD or AWD system after driving through rain/snow or simply going through a car wash.

CAUSE:
The speed sensor signal may have become corrupted. Possible openings in the speed sensor wire insulation (twisted pairs) can allow water intrusion. Also wire connections contaminated by water may result in short circuits and erroneous speed sensor readings. This most often occurs on the rear speed sensor circuit.

CORRECTION:
Inspect the wiring harness to the transfer case speed sensors. On Rainier, TrailBlazer, Envoy and 9-7X models, fabricate a replacement speed sensor harness between the C101 connector and the speed sensors. Completely inspect and test all wiring. Refer to Speed Signal Front Axle Actuator and Indicators schematic in SI.

Replace the affected twisted pairs. Do not over-twist the two wires in the replacement harness. Wires should be twisted at a rate of 9 revolutions per foot. Use service connector pack, P/N 88987993 at the speed sensor end and terminal, P/N 15326267, at C101.

Terminal testing tools and service terminals can be found in Terminal Repair Kit J 38125. Terminals are available from SPX/Kent-Moore.

The smaller transfer case harness splices into the larger chassis harness a few inches in front of the cross-member. The chassis harness routes along the left side of the frame under the driver door area. Use nylon tie straps to secure the fabricated harness to the main chassis harness between the transfer case and C101.

On the full-size pickup and full-size utility models, replace the 2.2 m (88 in) pigtail harness that runs from the C151 connector under the hood to the transfer case. Use either harness P/N 15832722 or 15224663 depending on vehicle equipment. Refer to Propshaft Speed Sensors Front Axle Actuator and Transfer Case Shift Control Switch schematic in SI.

Important: Technicians should verify the integrity of the splice joints after the repair. All splice joints and connections should seal properly against water or a repeat condition can occur.

Interesting. I think I'm going to go over the disconnected harness, including output shaft and front speed sensor harnesses.

I actually knew that about the encoder motor. Kind of works reverse of what you'd think, until it's explained.

I was talking about the actuator on the front diff -- it's commanded on in 4HI and 4LO, engaging the front diff fulltime. But it should be commanded off in AUTO, until the TCCM's speed sensors' input tells it to engage. That's the AUTO part of the mode, engaging/disengaging only the front diff.

Oh ok, gotcha. Have you tested the speed sensors before, or changed them? I'm waiting on a new encoder motor to get here and my garage is full...and the weather is bad so I'm not rushing to take it out just yet. I am going to tear down the old encoder though and have a look. With that removed I should be able to manually shift the transfer case.

 

[Fless]

Oh ok, gotcha. Have you tested the speed sensors before, or changed them? I'm waiting on a new encoder motor to get here and my garage is full...and the weather is bad so I'm not rushing to take it out just yet. I am going to tear down the old encoder though and have a look. With that removed I should be able to manually shift the transfer case.

I never had to inspect the speed sensor harness, since the encoder motor was the solution for me. If you have have a Tech 2 you may be able to view the T/C speed sensors' activity, if it comes to that. What I need to do is to get someone to chauffeur me around while I play with the Tech 2, to see what live data interests me. Too crazy doing it while driving.

When you shift the transfer case, it may help to have the driveshafts "free" by being in neutral and/or having it on four jackstands or a lift. We had to wiggle the rear shaft a bit to get mine to easily shift the T/C with the splined shaft.

 

[xDan]

Oh yea I saw the speed sensor data, all zeros.