[CNY_Dave]

Pins 19 and 20, rear VSS, are to the bottom left on the trans connector (T4) and to the right on the engine wiring harness (the connector displayed in the manual).

Word on the street is the white part pops out, then it's the usual pick-and-screwdriver work to retract the retaining tabs so the individual pins can be removed.

 

[CNY_Dave]

RVSS at the trans connector (and the FVSS) ohm out just fine, wonderful.

Either it's intermittent or there's a prob in the harness between the connector and the TCU, and the problem was just a coincidence.

Joy.

 

[ntippet]

Have you cleared the code and have had it return immediately?

 

[CNY_Dave]

Female pins on B11 to the TCU through the wiring harness is 60-160 kohms (depending on polarity) going to the FVSS input on the TCU, and mega-ohms for the RVSS. So looks like it's a harness-side not trans-side issue.

 

[CNY_Dave]

No, haven't cleared the code. You have to disconnect the battery to clear a TCU DTC code, yes?

 

[ntippet]

Disconnecting the battery might clear it, but I am not 100% certain on that.
FreeSSM will be able to do it without messing with the battery if you decide to go down that route in the future.
It would be wise to confirm this sensor (or wires) is actually the culprit before attempting any repair.

The measurements on the TCU side of the harness, how are you performing these?
Disconnecting the TCU connectors and measuring the ohms of each single wire from end to end (B11)?

 

[CNY_Dave]

I was essentially measuring the resistance of the signal input pins at the TCM, probably not relevant.

Harness checks out OK. 0 ohms (0.1 or so) for each lead between the TCU connector and the connector to the trans.

All the other diagnostic branches suggest it's either an intermittent or the TCU, as if a scope or the SSM or an AC voltmeter show no signal, it's ruled an either an intermittent or a bad TCM.

Would be funny if the TCM decided to go kaput right when swapping the trans.

 

[ntippet]

Alright good, I had a feeling you were measuring the internal resistance of the TCU on those pins.
Wouldn't suspect a TCU issue at this point...
I would start with seeing if it comes back.

Do you have a good multimeter or scope available to take your own readings?

 

[CNY_Dave]

Well, all that measuring and probing and leaving the batt disconnected, no more TCU codes but also no change in the AWD.

Since it seems to have a tiny bit of binding in a full-lock turn but no AWD I'm going to guess the clutch pack was abused and is no good, but I still can check the duty C solenoid, somehow.

I might be able to access a portable scope at work, if I place access leads first.

 

[cardoc]

It can't be the TCM. Maybe a bad ground inside at the valve body, loose ground off the harness, bent pin in the connector.

Your OE transmission was shifting and had AWD. Swap the valve body. Pull the rear extension and check the MPC.

 

[CNY_Dave]

I should be able to test for grounds etc at the trans connector, thanks for the idea. Duty C solenoid is a prime candidate of course.

Was it '05 and beyond where the duty-C worked 'backwards'? I read once one gen used it to allow pressure to build when energized, and another gen used it to dump pressure when energized.

I'd love to say *can't* be the TCM but I have seen 'simultaneous seemingly no reason for it to break at the same time' failures in the past.

With the pan off, I looked for anything 'amiss' and was careful not to pinch any wires.

I do have a few pics of the trans with the pan off, looked at 'em closely and I don't see anything obvious.

I'm a little concerned that the interchange info says a 2004 trans will go into a 2003, but a 2003 and 2004 TCU won't interchange.

 

[cardoc]

2004 was a odd year. It is considered a new gen in European and Japanese markets, where here, it still Gen 2. Changes were made to a lot of programming in advance of Symmetrical AWD.

 

[ntippet]

You are right CNY, I said that quite some time ago.
2004 & newer applies increased DC to the solenoid to increase pressure to the solenoid, before this is reversed.
The previous owner of the donor transmission has probably worn out the MPC.

 

[plain OM]

The reversal in the way the AWD solenoid works was accompanied by a change in the location of the solenoid and transfer valve. In the earlier set-up, they are located in the extension case. In the newer version, the AWD solenoid is integrated into the valve body. The valve bodies are different and perhaps the one you have can be identified by the difference - see attached.

 

[CNY_Dave]

ntippet, plain OM, did those changes make the TCU incompatible across that divide?

My TCU is 2003, my trans is 2004.

 

[CNY_Dave]

My 2004 valve body, looks to be the old style.

 

[ntippet]

Excellent question, something I hadn't thought about since I did not know the year of the transmission.

I would have to say the TCU is driving the solenoid incorrectly.
You can see from the tables that the throttle position is inverted for the MPC transfer pressure.
PlanOM, confirm?

EDIT: Looks like you got a post in before I finished.
Interesting you have the old style valve body, could mean that it does in fact match.
Could have something to do with the build date of your 04'?
The 04' manual clearly shows the valve body is the newer design.

04' Manual

Pre 04'
Edit: See post 32 for he correct chart.

 

[CNY_Dave]

Excellent question, something I hadn't thought about since I did not know the year of the transmission.

I would have to say the TCU is driving the solenoid incorrectly.
You can see from the tables that the throttle position is inverted for the MPC transfer pressure.
PlanOM, comfirm?

EDIT: Looks like you got a post in before I finished.
Interesting you have the old style valve body, could mean that it does in fact match.
Could have something to do with the build date of your 04'?
The 04' manual clearly shows the valve body is the newer design.

04' Manual

Pre 04'

Could you point out the diff in those 2 pics? I see the pressure diff, but is there a diff in the pics?

The donor is an '04, I could probably get the salvage yard to get me the manufacturing date.

Maybe LL beans with the H6 didn't have the change applied in '04??

Is the date in the trans ID somewhere? This is the donor trans (2004) tag:

 

[Glennda5id]

Based on part numbers the 03 and 04 transmissions were interchangeable. Differences in the TCU between 03 and 04 could have to due with differences in the 03 and 04 ECU.

You should be testing the solenoid at the extremes. For that year car when the solenoid is energized then there should be no AWD correct? And when it is 0V, it should be full 50/50 AWD. Can you induce those conditions?