[ntippet]

I don't have a scope trace but I can tell you exactly how the 04' works.

Its posted up on here from some time back, but I will re-write it for you.

These are all measurements I took from backprobing the circuit under operation.
Also used a clamp on ammeter.

Here is how it works:
12V VDC constant 50Hz power side switched
Grounded inside the transmission case
PWM controlled
12.6 ohms resistance across the solenoid and circuit
Gear | Duty Cycle | Amperage | Voltage
P - | 5% | .01A | .14 V
R - | 42% | .16A | 3.6 V
N - | 5% | .01A | .14 V
D - | 42% | .16A | 3.6 V
3 - | 42% | .16A | 3.6 V
2 - | 42% | .16A | 3.6 V
1 - | 55% | .27A | 5.3 V

Increased duty cycle is delivered in a linear fashion the further the throttle is opened. (when stationary)
Example: In drive, throttle 50% open, duty cycle is 75% amperage is .61

Full DC (95%) is achieved only under a single circumstance I have found.
100% Throttle Engagement under ~5mph
This delivers a maximum of 95% duty cycle and 0.95 A to the solenoid.
As soon as you begin to move it falls off quickly.
The TCU does not take into account rear VSS for wheel slippage & increase DC.
VSS has no input on transfer clutch lockup, went into extensive testing on this.
Have to dig through the FreeSSM thread to find it though.

Models before 2004 this is all reversed.
Disengagement is achieved by increased duty cycle.

 

[ntippet]

Yes it driven on the +12V high side, 50Hz square wave.
When I say high side I mean the positive wire of the solenoid, the ground wire is inaccessible unless you disassemble the transmission & rewire it away from the case.

Its actually a maximum of 95%, never 100.
Also not applying PWM to a portion of the pulse.
Its simply a square wave with a % of on time vs off time (duty cycle).
Your vehicle's TCU is trying to turn off the solenoid using 95% DC, when the "new" transmission needs a 5% DC to be turned off.

 

[ntippet]

Correct, it is a percentage of on vs off time.
Which is constantly being driven at 50Hz frequency, never changes.

 

[ntippet]

I haven't opened up one but chances are high the TCU is all smt components coated in epoxy.

With the KOEO the solenoid is still driven the same as with KOER.
Key off there is nothing driven.

 

[ntippet]

Nice, thats good to know.

Yeah probably MOFSET or PNP type Darlington or equivalent.

 

[ntippet]

Its necessary for me, since I don't want to stare at the AT Oil light, besides if something else goes awry in the tranny I want to know about it.
My intent was to make everything work as it was intended & let the TCU think it was still controlling it.
10W of power dissipation is all that is needed.

It doesn't cause any damage, code yes..

 

[ntippet]

It is still possible that the MPC is worn out.

It took awhile but I finally found the post where I performed a special test basically turning off the TCU control and leaving my controller at 0%.
Recorded how the TCU "should" have responded to F & R wheel speed differences, in the end it did not increase DC to the transfer clutch to compensate.

http://www.subaruoutback.org/forums/65-parts-accessories-performance/39426-freessm-complete-access-your-ecm-tcu-33.html#post381806

I will have to dig through that thread some more as to why you are experiencing that with your AWD now.
There is a ton of info, just takes a while to find what you're looking for.

 

[ntippet]

Yeah shouldn't be too difficult to trace the solenoid pin from the connector back to the output of the transistor.
Take some photos, would like to see the inside of the TCU, don't feel like taking mine out.

Have fun with the lockup, it does make a difference, I find it much more fun in the snow.
Automatic control of the transfer clutch makes the car much too boring and stable/predictable.
But that's why it works so well.

 

[ntippet]

Mine is also remotely mounted there.

 

[ntippet]

Getting closer to something custom.
Does your resistor keep the AT Oil light from tripping?

 

[ntippet]

Are you pouring through the service info on the 03' and 04' looking for the difference?

 

[ntippet]

CNY if you have a multimeter capable of reading % you should add that to your chart.
Will give you the actual duty cycle the TCU commanding, otherwise you would have to infer that from the voltage readings.
Since the DC voltage readings are just taking an average of the highs and lows from the digital PWM square waveform.

plain OM I looked up the part #'s for the transfer solenoid, 03' and 04' are definitely different.

03' - 31942AA103 (spec'ed for 99-03')
04' - 31942AA130 (a bulletin 16-67-04 was released to replace 31942AA120 with 31942AA130, you should know though you have posted on this subject in the past)

New style solenoid started production in October of 2003 with transmission number 012485.

Edit:
Have been trying to find some good photos of these solenoids & differences.
Not much luck but came across an interesting thread & it looks like the Russians have also been mixed up on the 03' - 04' change as well.
Best viewed through Google translator.
http://forums.drom.ru/subaru/t1151877849.html

 

[ntippet]

CNY I am starting to think if you take the valve assembly and solenoid off your bad 03' tranny and swap it into the new one it may work correctly.

As plan OM noted the transmissions themselves haven't really changed at all.

I would bet the differences are not only in how the solenoid is controlled but also the internal valving control & fluid control between duty solenoid/control valve/feed to the clutches.

Since the parts are small valve assemblies, including the solenoid, they may be swappable.

Unfortunately I do not have the 2 different parts sitting on a bench so I can confirm these suspicions.

 

[ntippet]

I was referring to the small valve assembly that accompanies the transfer solenoid, not the entire transmission valve body.

 

[ntippet]

At least taking off the extension housing isn't too hard, the only components in the way are the exhaust and driveshaft.
Tranny does not have to go anywhere, although it sounds like CNY might leave that project for another day.

 

[ntippet]

Yes and Yes.
Typically will drop the entire exhaust in 1 piece, from the headers to the muffler.
Never have to bother any of the flanges this way.