No AWD but no codes under normal use

No AWD but no codes under normal use

Postby zGerman [OP] » August 22nd 2019, 10:07am

Hello all! I think the answer is encoder motor but I wanted still ask before I spend $120 and an hour under the van.
I have a 2001 AWD but it really is a RWD at this time. I have no codes and the relay under the dash clicks once when I turn on the ignition. The ATC fuse is OK. The AWD light is off but working. I can force an error when I run up a steep hill and let the rear spin for 10-15 seconds. With the brute force method of letting it spin I get the expected C0374 error. So I came to the conclusion that the control unit is at least somewhat alive and working and the sensors are fine too. Seems like the encoder motor does not engage the T-case in to AWD.
Dear wizards - is there anything else to try or should I order a new Transfer Case Shift Encoder Motor?
2001 Astro conversion van AWD 4x4 - 2+1 lift, 16x8 wheels, 245/70-16 tires, 2 inch wheel spacers, Jeep front bumper, NP231 and Jeep Liberty shifter.
Rudimentary camper build tailored to my needs with 200W of solar, a fridge and a diesel heater.
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Re: No AWD but no codes under normal use

Postby zGerman [OP] » August 25th 2019, 4:25am

I purchased and installed a new encoder motor. The install was easier and quicker than expected but the result is unchanged. Since I had the front drive shaft off I also know now that the tcase front output spins freely when parked. The front axle does transfer torque, when tightening the u joint bolts the vehicle rocked back and forth.
So the transfer case does not engage. Any suggestions to what to do next?
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Re: No AWD but no codes under normal use

Postby Mmusicman » August 26th 2019, 9:01pm

It would be nice to know if the encoder is getting a signal to engage, and is in fact engaging.
There are ways to test it.. to read the signal, or to send it your own temporary test signal.. but it's tricky.

The system uses PWM (pulse width modulation).. so you would need to know what you are looking at.
FWI: There is a place in the DS kick panel with 2 heavy gauge wires that feed the encoder.

You could drain the oil and see what comes out.
These units have clutches that "can" go bad, just like a transmission.

I've tested my AWD (in the past) by raising the rear tires off the ground, and see if the front pulls you.
I used a floor-jack (under the rear differential) on a smooth surface so it could be pulled along.
You would need to know how to do this safely however, as well as only moving a few inches.

There are many issues with this complicated AWD system, both testing and operational.
Typically, if the controller sees both prop-shafts spinning same rate, it won't throw a code.
But as you have already figured out.. both shafts turn regardless of AWD engagement or not.
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Re: No AWD but no codes under normal use

Postby zGerman [OP] » August 27th 2019, 4:03am

Thank you for the reply. I did order some of the proper Auto-Trak II fluid and do that next.
I actually have an oscilloscope in my shop so I just need to figure out how to identify the correct wires. I also thought of maybe pulling the harness in to the dog house (if that works) and plug it in to the encoder. Than with the lifted rear as you described tickle the controller in to engaging it. Basically I should see the encoder motor turn a bit say 1/8 or 1/4 turn if all is well.

I am not going to rebuild any clutches but rather gather the parts for an NP-231C swap instead. If I have to take the t-case out anyway it will be evicted in favor of 4x4 and low range.
2001 Astro conversion van AWD 4x4 - 2+1 lift, 16x8 wheels, 245/70-16 tires, 2 inch wheel spacers, Jeep front bumper, NP231 and Jeep Liberty shifter.
Rudimentary camper build tailored to my needs with 200W of solar, a fridge and a diesel heater.
100046
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zGerman
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Years of Membership: zGerman has been a member for 1 full year
Posts: 27
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Van Model Year: 2001
Van Make/Model: Chevrolet Astro
Extra Info: Explorer Conversion

Re: No AWD but no codes under normal use

Postby Mmusicman » August 27th 2019, 9:39pm

zGerman wrote:Thank you for the reply. I did order some of the proper Auto-Trak II fluid and do that next.

The "correct fluid" isn't going to suddenly give you AWD operation.. unless t-case is empty.
In that case you will have more serious issues.
The Auto-Trac II mostly resolves issues with turning and binding.

I actually have an oscilloscope in my shop so I just need to figure out how to identify the correct wires.

If I'm not mistaken, there are only 2 main engagement wires to the encoder?
As I mentioned, you can actually pick them up in the DS kick panel (left of parking brake)
I believe the wires are black.. about 14-16awg. At one time I was going to wire these though a relay so I could manually engage the encoder with 12v.. but it is unclear if direct 12v would burn up the encoder... or if it would work for a certain amount of time. This would certainly be an easy place to take some o-scope readings. I believe there is a wealth of info on the PWM signal out there on the web.

Than with the lifted rear as you described tickle the controller in to engaging it. Basically I should see the encoder motor turn a bit say 1/8 or 1/4 turn if all is well.

I may have read that you can damage the encoder if engaged while not installed? .. not sure.

FYI: Lifting the rear wheels in drive WILL engage the system (if working properly).
The split-second it sees the rear's turning and the front's not, it will immediately engage.

I am not going to rebuild any clutches but rather gather the parts for an NP-231C swap instead. If I have to take the t-case out anyway it will be evicted in favor of 4x4 and low range.

The 231C is a great manual upgrade option, as well as the 233C.
In my opinion, both require about the same amount of work.. just in different places.
I think the 233C may have a thicker chain and be stronger internally too.

If you don't need AWD.. then manual operation is the way to go!!!
No encoders to burn out, no sensors, no special fluid, no clutches, no electronic controllers, wiring, connectors, etc.
Just pull a lever and go!

Here's my 233C upgrade conversion: (direct bolt-on)
https://www.astrosafari.com/viewtopic.p ... 9&t=136058

I needed 4x4-Lo.. my AWD absolutely could not do this: (I tried once previously)
(Pulling about 5000 lbs slightly uphill in soft sand)

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2000 Astro LS 4x4 | NP233 | 31" LT265/70R17 Tires | 8" LIFT | 10" TOTAL
92 Chevy Astro Cargo Shorty | V8-350
http://www.CruisinSouthFlorida.com
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Posts: 4838
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