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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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Discussion Starter #1
I am hoping, beyond what I can search here, someone has or has seen a good scope trace of the Duty C signal. In a perfect world, there would be a trace from an '00-'03 and one from an '04, when apparently the signal polarity was changed.

Before '04, +12V to the duty C disabled the AWD, '04 and above, +12V fully activates the duty-C and the AWD.

What I am hoping is that I can get reasonably close to the proper signal by using a few transistors to 'invert' the signal.
 

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2009 Tribeca Now - 2004 Outback EJ259 - Sold
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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.
 
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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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Discussion Starter #3
Thanks.

50HZ with PWM applied, so 100% duty would be a 50hz square-wave?

I assume the PWM is applied to the +12V portion of the pulse.

If that is so and the '03 uses the same signal but the PWM applied to the 0V portion of the pulse, a simple inversion of the driving circuit would function just fine, I think. The proportions would even match.
 

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2009 Tribeca Now - 2004 Outback EJ259 - Sold
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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.
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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Discussion Starter #5
OK, so at 50% it's a 50HZ square wave, equal time at 12V and equal time at GND.

So if the new trans is supposed to see "75% locked" (not really 75% locked, I know), the TCU would send it a signal that was 12V 75% of the time, GND 25% of the time.

My 03 TCU will drive the signal to be GND 75% of the time, 12V 25% of the time.

So, all will be well if I take my TCU output and create a simple circuit that will feed +12V when the input is GND/float, and GND (or float?) when the input is +12V.
 

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So, all will be well if I take my TCU output and create a simple circuit that will feed +12V when the input is GND/float, and GND (or float?) when the input is +12V.
I like your plan of attack. Have you looked into what the values should be when the engine is not running or in any other mode, just to make sure you don't upset the TCU somehow?
 

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2009 Tribeca Now - 2004 Outback EJ259 - Sold
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Correct, it is a percentage of on vs off time.
Which is constantly being driven at 50Hz frequency, never changes.
 

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Discussion Starter #8
I like your plan of attack. Have you looked into what the values should be when the engine is not running or in any other mode, just to make sure you don't upset the TCU somehow?
Lacking a set of scope traces for every eventuality, no.

But, it seems that the 03->04 change involved just 'flipping' the signal, so behavior should match. Even inserting the FWD fuse will work correctly, assuming the TCU is told to send +12V vs there being another device in the circuit that just pins it to +12V.



I don't think the TCU can get any feedback/info, in any case.

What I would really like to do is to modify another '03 TCU and manipulate the transistor circuit, or invert the low-level signal going into the drive transistor.
 

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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.
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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Discussion Starter #10
I had my TCU cover off and it was SMT except for the drivetransistors, which were through-hole. Even the SMT stuff you could solder a wire to, not too bad.

If I could just 'swap the power' to the transistors or such that's be perfect, but I would have to see what type they are and what config they are used in.

They are probably power MOSFETs.
 

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Nice, thats good to know.

Yeah probably MOFSET or PNP type Darlington or equivalent.
 

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Discussion Starter #12
ntippet, have you found the load resistor replacing the solenoid as necessary?

I would not imagine disconnecting the duty c would cause damage, but I recall there was some concern doing so would throw a code.
 

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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..
 

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Discussion Starter #14
OK, if I end up leaving the TCU connection off I'll add a resistor, temporarily maybe or maybe not.

I am thinking of disconnecting it until I get it squared away so I don't cause undue clutch plate wear, although at speed it should be about the same.

Now, where I am less clear on the why, if in D it is 42%, on my car/trans combo that would be 58%, why does it act like it has no AWD at all?
You mentioned the rear VSS has no effect on the duty cycle, I thought its whole reason for existence was to detect slip and increase the duty cycle?

Maybe 2004 does not work that way, but 2003 does?
 

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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.
 

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Discussion Starter #16
I recall the TCU had a bunch of 5 pin devices on it, which I think are the drivers:
HA13705C



If this is the case I could pull the input pin (CMOS level stuff) and wire in an inverted signal from an inverter, and the solenoid signal would be inverted.


 

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The attached photos are supposedly showing the change in the extension housing when the 4EAT Phase II was modified to "direct control", which included the relocation of the AWD solenoid and the "reversal" of the control programming. The later tail section appears to have different "ribbing".

I'm not sure if the change was coincident with the introduction of MY2004 cars, or actually effective with MY2005 for the Outback, although I guess that's moot at this time. (Subaru often phases in such changes, with some models getting the newer version earlier.)

The valve bodies certainly would not be interchangeable.

ntippet's waveform explanation of duty cycle % is excellent!

With the 4EAT that has the multi-plate clutch transfer system, the rear VSS is not necessary as far as rear wheel spin is concerned because the rear drive (shaft) cannot turn faster than the drive to the front differential -- it's simply impossible if nothing's broken.

This does not take into account what one wheelmight do as the front and rear differentials will allow one wheel to speed up while the opposite wheel slows down. However, the VSSs are monitoring the drive shaft speeds, not individual wheel speeds.

The rear VSS is used as a reference; the TCM compares the front and rear VSS signals and should adjust the duty cycle if the front VSS is showing a higher speed than the rear VSS. The basic logic of the AWD system is that the two drives be turning at essentially the same speed and if they're not, it increases the clutch pressure to effectively lock the drives together.

Note: The TCU also uses "torque" as an input to it's duty cycle control. In the FreeSSM post that ntippet linked, the third chart shows the front wheel speed (VSS) ramping up while the rear wheel speed (VSS)remains low, yet the duty cycle does not peak out. However, in this particular case, as I recall, the front wheels were intentionally allowed to spin and with the rear drive effectively disconnected, there was little torque being developed in the drive train. Later on we examined the impact of torque as represented by the difference ("delta") between engine rpm and torque converter turbine rpm. This appeared to be a significant, if not overriding determinant of duty cycle.
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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Discussion Starter #18
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.
What I can say on my end is that with the FWD fuse in place, 12V to the solenoid, I could not induce front wheel wheelspin relative to the rear.

Hopefully there is plenty of snow to play in on my way home.
 

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Discussion Starter #19
The attached photos are supposedly showing the change in the extension housing when the 4EAT Phase II was modified to "direct control", which included the relocation of the AWD solenoid and the "reversal" of the control programming. The later tail section appears to have different "ribbing".

I'm not sure if the change was coincident with the introduction of MY2004 cars, or actually effective with MY2005 for the Outback, although I guess that's moot at this time. (Subaru often phases in such changes, with some models getting the newer version earlier.)

The valve bodies certainly would not be interchangeable.

ntippet's waveform explanation of duty cycle % is excellent!

With the 4EAT that has the multi-plate clutch transfer system, the rear VSS is not necessary as far as rear wheel spin is concerned because the rear drive (shaft) cannot turn faster than the drive to the front differential -- it's simply impossible if nothing's broken.

This does not take into account what one wheelmight do as the front and rear differentials will allow one wheel to speed up while the opposite wheel slows down. However, the VSSs are monitoring the drive shaft speeds, not individual wheel speeds.

The rear VSS is used as a reference; the TCM compares the front and rear VSS signals and should adjust the duty cycle if the front VSS is showing a higher speed than the rear VSS. The basic logic of the AWD system is that the two drives be turning at essentially the same speed and if they're not, it increases the clutch pressure to effectively lock the drives together.

Note: The TCU also uses "torque" as an input to it's duty cycle control. In the FreeSSM post that ntippet linked, the third chart shows the front wheel speed (VSS) ramping up while the rear wheel speed (VSS)remains low, yet the duty cycle does not peak out. However, in this particular case, as I recall, the front wheels were intentionally allowed to spin and with the rear drive effectively disconnected, there was little torque being developed in the drive train. Later on we examined the impact of torque as represented by the difference ("delta") between engine rpm and torque converter turbine rpm. This appeared to be a significant, if not overriding determinant of duty cycle.

I will have to compare against my trans pics.

I meant front wheels spinning faster than the rears, indicative of slip.

Thx.
 
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