Hi, (a new Blazer 2000 LT 4.3 User!)

I've just bought my truck and the 4x4 system is not working (quite common, I've read all the threads about it on here) ..

There's one thing I couldn't find tho, it's the voltage on the 4 pins connector that feeds the T-Case encoder Motor.. I thought I would see 12 Volts on Black and 12 Volts on Red, but I have 12 Volts on Black and 5 Volts on Red..

I believe this is a problem, it sounds like one of the drivers in the TCCM is shot and is sending logic voltage to this pin.

However, the Black (5volts) goes to ground when I try to go in 4Hi or 4Low, so I believe that at this point the encoder should move. However it doesn't and it sounds like the encoder motor is shot because I don't hear it when I am under the truck when someone pushes the 4Hi button..

I diagnosed my 4x4 with the help of this forum, thank you very much btw!!

And my vacuum actuator works perfectly, I also can hear the clicking in the TCCM and under the T-Case Encoder I hear the solenoid lock also but not the motor..

I'm in the process of buying a new encoder motor, however I am wondering if my TCCM is okay..

Also, I have these resistance values on the Speed sensors: E13 320 ohms, E12 1870 ohms, F5 1870 ohms, F6 320 ohms.

E16 Ground pin compared to vehicle body ground is 320 ohms (a bit high I believe) ..

E16 to ground on 4 pin connector is 0 ohm.

The speed sensors should read between 1300 and 2700 ohms I've read, but the Low Speed pin, I am not sure what it is .. (Probably a path to ground, thus 320 ohms since there's 320 ohms to my body ground)


I am also wondering if there would be a market for home made TCCM, I do a bit of electronics and microcontrollers, I believe I could easily make an open source or sell DIY TCCMs..

 

Anybody with a multimeter can help me?!

 

Anyone!? I just need to 2 voltages on the feed motor pins...

 

Anyone!? I just need to 2 voltages on the feed motor pins...

 

Should be +12V & ground to the red/black wires at the shift motor in the encoder motor assembly that switches depending on the intended direction of the shift. If you are getting +5V, you either are not measuring on the proper wire or there is a problem with the wiring.

As far as your endeavors, I wish you luck, but I think it's a waste of time and energy. While I could re-engineer the TCCM, I can more effectively (both cost & time wise) spend my time on other things.

As far as auto operation goes, I doubt you will be able to build that into your implementation. The TCCM samples the front & rear prop speed sensors and adjusts the load on the clutch pack accordingly until the speeds match for a set period of time, then unloads the clutch pack, returning the transfer case to 2HI mode; all the while, the front axle remains locked in.

Another thing worth mentioning that the NV236 has an integrated brake in the encoder motor assembly. This brake must be energized to disengage it and cannot stay energized for very long or you could risk overheating the coils. Each time the TCCM needs to adjust the load on the clutch, the brake is energized, the adjustment is made, then the brake is de-energized.

 

Thank you for your answer!

I agree with you that it's a waste of energy, in the end, I don't feel like doing it, but I don't feel like buying a new TCCM ..

The clutch pack is driven by the encoder?
The solenoid is the brake you are speaking of? I thought I'd have to unlock the solenoid then moving the encoder to the desired position and then lock it back.

As for the Auto4Wd, I think it's only a matter of creating a PID loop in a AVR microcontroller and driving the clutch pack in relation to the speed difference between rear and front..

What I really don't understand is how to drive the clutch pack, if it's on the encoder motor, I see the solenoid as being a kind of mode selection between gear position (4HI, 4LO or 2HI) and the clutch pack.

Thanks for the information!
I think I test the correct wire, it's on the 4 wire connector, it's the one next to the RED one. The wire stay's high at 5v the RED one is at 12v and that is when the encoder is idle.

On mode selection the 5v goes to ground while the Red stays at 12v, effectively trying to drive the encoder.. So the hbridge driver in the TCCM is shot in my opinion, one thing I could try is isolating the component at fault in the TCCM and fixing it.

I also don't have the latest TCCM part number.

I think I'm going to just buy a TCCM and an encoder motor in the end, but well, yeah I don't feel like paying it :P

 

The clutch pack is inside the transfer case. Take a look at the NV236 exploded view on drivetrain.com. The encoder motor turns the shift sector shaft which applies force to the clutch pack varying the degree of engagement, thereby varying the amount of torque to the front axle from 0/100 F/R to 50/50 F/R relating to 2HI & 4HI respectively.

The brake locks the encoder motor itself once the TCCM determines that the shift sector shaft is in the proper position. It is just a solenoid that pulls back on the brake assembly.

The TCCM determines the shift sector shaft position by monitoring the states of the various channels from the encoder portion of the encoder motor. While not exactly like the encoder found on the NV233 transfer case, it is similar. I have disassembled & documented the encoder found in the NV233 in the Tech Article (DIY) section. I'd like to do the same thing with the NV236, I just need to have someone send me an encoder.

 

Isn't the NV236 a hall effect encoder!?

I've just bought a nv236 encoder with a new TCCM I plan on repairing my old encoder I'll post pictures when I'm done.

 

Here are a few articles on the NV246, the big brother to the NV236:
New Venture NV246
New Venture NV246; Tricks
Courtesy of RSGear.com

The encoder section is a contact type position sensor much like the transmission range sensor. It is not a hall effect sensor like the CKP, WSS, CMP, etc sensors which are required to be hall effect because they are non-contact sensors due to necessity as they are dealing with fast rotating components where contact type sensors would wear out far too quickly.

In my experience, what actually goes bad in an encoder motor is either the windings in the brake solenoid, the windings in the encoder motor itself, or the gears in the encoder. Rarely is there an encoder fault in the encoder portion of the encoder motor assembly, but it can happen. Winding faults are fairly easy to diagnose by measuring the resistance across the coils while applying a voltage. If the resistance goes to infinity (or really, really high), then the winding is bad. Even when an encoder fault is indicated by the TCCM, it often can be traced back to corrosion and/or other wiring problems and not directly related to a fault in the encoder internal to the encoder motor assembly.

Concerning the 5V you are getting to the encoder motor, have you disconnected all of the wiring & made sure that nothing is shorted out somewhere in a harness out of sight? I would hate to see you get all new parts and still have the same problem.

 

Well I already bought the TCCM and encode motor.. The TCCM I bought is the newer part number btw, the one I had is not.

I don't think there was a short in the harness, in fact I thought it might have been the winding of the motor, but now that you say that, I'm going to check that right now..

In any case, if I bought the TCCM or encoder for no reason, I'll just sell them back on ebay..

I'll be back, I'll check the resistance to ground of the motor feed harness..

Ok so there's 1.6 MEGA ohm to ground on the RED and Black Feed wires. No short to ground there.. I unplugged the 4 wires harness from the TCCM but kept the large connector on and turned on the truck.. There was no voltage on the RED or BLACK, so I don't think it's a short in the harness, if it was shorting to a 5 volts carrying wire, it would be one of the large connector.

There is also no short between Red and Black but it was in the Mega Ohms between them which I believe is and open coil in the encoder motor.. I don't understand the 5volts though, this is msot probably a TCCM problem, like a shorted MOSFET..

Also, I hear the solenoid clicking in the NV236 and I checked the voltage of the encoder channels and they don't change.

Oh and also, the ground wire in the harness to the body of the truck is showing 300 ohms, is this within specs?

Thanks!

Btw, I might be slow or something but I still don't understand the clutch plate design, even with the diagram.. It looks like according to the diagram that the clutch plate lives inside the motor.. And I don't understand how the motor can have 2 functions, one function applying clutch pressure and another one gear selection..