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Old 01-27-2006, 07:19 AM   #1
west_minist
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w/ AVCS Silver

Default TCU outputs for controlling the ECU on 4EAT

Hi there!

I am trying to understand the interface between the TCU and ECU to see how the TCU signals the ECU for shifting.

So far, I know of only 2 output & 1 input signals:-

Output
1) Torque Control 1 Signal - Reduces engine torque during range selection and gear change.

2) Torque Control 2 Signal - Reduces engine torque during range selection and gear change.

I do not see why there is 2 instead of 1.

Input
3) Torque Control Cut Signal
Sent from engine control module (ECM) to TCM to temporarily inhibit the torque control when starting off with low coolant temperature.

4) AT Load Signal - Could be the diagnostic signal

I have monitor these signals and do not see much with logging tools when shifting, especially the Torque Control 1 & 2 signals

How do these signals change on the 4EAT with shifts from 1-4?
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Last edited by west_minist; 02-06-2006 at 12:28 AM.
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Old 01-29-2006, 10:43 AM   #2
west_minist
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Bump Bump
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Old 02-06-2006, 01:51 AM   #3
PHATsuby
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to stock is a project too

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if you have the tech pdf then look under the mechanism and function sections and look at the TCU or tranny components and see if it describes when or how it takes input and output to control shifting.

also, look at the wiring diagram, look at what wires go to the TCU that also go to the ECU and see what they show for voltage range and if you can use it or take it from the hydra. Or if it is coming directly from a sensor.

Instincts tell me it probably wont really matter much, but i havent looked into your wiring at all. You may get some different characteristics on cold temp shifts if it operates how you say, but it will still shift likely based on load and rpm so if it receives those signals it should work.

If I have time i'll look at my pinouts more and maybe come up with a better idea of what is happening.

Ben
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Old 02-06-2006, 08:10 AM   #4
west_minist
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I think, looking 99+ RS auto's should give the same result.

I have the tech doc on the TCU, thats how I manage to have some idea on the outputs and inputs. But from the logging, there do not seem to say much. I would have to test for it w/ full throttle and let it shift in 3rd and then light throttle in 4 to see changes.

So far, if I am correct, the TCU send outputs to the ECU to reduce engine rpm for shifting.

is there a tracer tool you can use like the telephone people for tracing electrical wires? I think there are tone generators.
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Old 02-06-2006, 09:07 AM   #5
bigdweeb
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I know Kha0S was working on a project a while back to control the center diff... Do some searching for his name and TCU

To get you started...
A walk-through of the VTD-AWD system...

The link in the top of that thread was about the project he was working on.
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Old 02-06-2006, 09:09 AM   #6
west_minist
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Many thanks. I have to go and drive in the wet Unfortunately to do some business
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Old 02-06-2006, 01:25 PM   #7
Legacy777
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If you're looking to replace the ECU with aftermarket, and keep the stock TCU, you'll probably have to send some form of signal to those inputs. What have you been logging with, and what are you logging? DC volts, AC volts, range?
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Old 02-06-2006, 05:47 PM   #8
west_minist
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logging software w/ ecutek and ecuexplorer.

I would like to get rid of the auto, but I cannot at this point and the Hydra cannot control the auto.

So I need to know what those three does?
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Old 03-19-2006, 05:55 PM   #9
west_minist
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Ok. I have logged the car w/ DD and those signal does not correspond to shifting, like what I expected.

So I am wondering on how the L series and legacy shifts. So I think that in the engine bay, thre is a selenoid ontop og the engine of mind, @ the side in the legacy that seems to control the vacuum. All I know that timing is pull from the engine.

If that is the case, I do not see the usage of TQCS1 & 2. I don't have a portable oscilloscope to test w/.
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