[CNY_Dave]

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.

 

[CNY_Dave]

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.

 

[CNY_Dave]

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.

 

[CNY_Dave]

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.

 

[CNY_Dave]

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.

 

[CNY_Dave]

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.

 

[CNY_Dave]

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?

 

[CNY_Dave]

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.

 

[CNY_Dave]

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.

 

[CNY_Dave]

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.

 

[CNY_Dave]

I have the older style, and have confirmed I have the older valve body.

 

[CNY_Dave]

H6 vehicles have the filter remoted to the front fender, under where the battery fits.

 

[CNY_Dave]

This weekend I will probably get as far as adding leads for a meter and measuring my TCUs signals, and if they (voltage) are similar to the 04 voltages posted by ntippet, I'll presume inverting the existing signal is reasonable.

Maybe I'll get as far as pulling the TCU again (easy) and IDing the actual solenoid driver chip.

 

[CNY_Dave]

OK, some progress.

Have my TCU out, have traced the circuits for the Duty C output.

Device is a Sanken Electric SI 5151s.

Similar to the hitachi device above, but opinout is:

1- GND
2- SIGNAL IN
3- Vo (output)
4- Diag (what the TCU uses to tell if the solenoid circuit is shorted or open)
5- Vs (presumably +12V)

SIGNAL IN can be a TTL or CMOS input, I'm thinking of snagging an inverter (will have to measure if these are +5V or 3.3V circuits) and just invert the signal to the driver.

This driver can source 1.8A, 1.5W as installed without a heatsink (18W with).

I wonder if I can find an inverting driver I can use instead?

Other driver devices on the board are 5155s (2.5A) and 5153s (2A but built-in zener).

Links I found that led to the info-

PGMFI.ORG - Grassroots ECU Development - Library . OBD1CivicIntegraECUs

http://wikitest.pgmfi.org/twiki/pub/Library/OBD1CivicIntegraECUs/SI-5151S.pdf

http://www.littlediode.com/datasheets/pdf/Datasheets-SI5/SI5155S.PDF

SI-5153S datasheet, Pinout ,application circuits High-side Power Switch ICs [With Diagnostic Function, Built-in Zener Diode] SI-5153S

 

[CNY_Dave]

Finding pwr and gnd would be a lot easier if I could ID any of these ICs:

Mitsubishi M59550 FP, and M59350

No logo, marked 5223, I don't think it's a MAX5223.

The 59350 might be a watchdog timer/power IC.
The connections make sense.
M59350FP pdf, M59350FP description, M59350FP datasheets, M59350FP view ::: ALLDATASHEET :::

 

[CNY_Dave]

A thought occurs to me- if I invert the signal going to the solenoid driver, I may also have to invert the monitoring signal from the driver to the microprocessor.

I just noticed something else- the FWD fuse does NOT connect the TCU pin to +12V, it connects it to ground.

 

[CNY_Dave]

Also, to avoid activating a code/flashing AT Temp light, a resistance of something less than 30k ohms needs to be between the solenoid output and ground, the open circuit sensor has a max trip resistance detected of 30k ohms.

No power resistor required, and need never be switched out of the circuit.

 

[CNY_Dave]

Well, my temp mod is done.
Wired up a DPDT center-off switch so I have:
- normal connection
- transfer solenoid disconnected to give me front-wheel-drive
- FWD switch active, which gives me 'locked' AWD.

I went by the specs on the driver chip, which said a 30k resistance would keep the open-circuit alert from tripping, wired in a 10k, apparently iot does need to be less than that.

I have GND and the sig from the TCU coming up to where I can get to them, so I can add a resistor and see where the cutoff is.

I also have a set of voltage measurements to compare against (at some point) for all gears, at idle, mid-throttle, and full-throttle, measured AC and DC.

Looking at the valve bodies, 2003 vs 2004, no visible differences.

There are a few external differences on the bellhousing, though.

 

[CNY_Dave]

I am fairly certain it's not a VDC transmission, I think there were several pins I have checked that are in different places on a VDC trans.

The 10K resistor is I guess too large to prevent the tripping of the AT light and flash.
Gives me an indicator I have it in 'Front' WD mode. The FWD light comes on to tell me I'm in 'Four' WD mode too.

I probably won't go through the '04 manual, I need to figure out either a transistor inverter circuit or mod the TCU itself with an inverter gate. I'll have to desolder the entire 5-pin driver to lift just the one (input) pin, and might have to invert the monitoring output as well.

The subaru dealer confirmed that '04 is different, as have the measurements and mods by ntippet.

 

[CNY_Dave]

Wonder if anyone else will be able to read this, heh.