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5EAT TCU Reverse Engineering


utc_pyro

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That was Msprank(?) With the 08 valve body. He described that as something they used to match the impedance so the tcu would not throw a code (as if the actually changed the solinoids), but thinking about it I think you are right. It was just a cheap simple way for them to bump up the line pressure. Edited by utc_pyro
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Thats me. I have the external resistor. Porcelain style. Like you get at Radio Shack. I can see it zip tied to a harness of wires. I can take a pic and check resistance value. The car is on stands while I strip it since it got rear ended. My VB is for sale too, lol. It is the very first 2008 VB IPT ever did. I drove the car there and left it with them for the day. Edited by m sprank
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Thats me. I have the external resistor. Porcelain style. Like you get at Radio Shack. I can see it zip tied to a harness of wires. I can take a pic and check resistance value. The car is on stands while I strip it sine it got rear ended. My VB is for sale too, lol. It is the very first 2008 VB IPT ever did. I drove the car there and left it with them for the day.

 

Yep, that would be a "power resistor", capable of handling higher current. If I'm reading the speck sheet right on the leniar current regulator the TCU uses to regulate the pressure, it can put out a few amps.

 

If you could take a pic AND check the value it would be much appreciated. When checking the value, you'll see the resistor and the solenoid's current in parrellel. If you can see a value marked on the resistor, we can back out the coil impedance. I can compare that to the coil impedance on my car, and give you all a value that will work on an 05/06/07(?) as well.

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I think it was external because his was the first 08. There was a ECU and valve body change in 08. If they needed they just changed the resistor right there instead of getting into the valvebody (drain fluids...)

5eat downshift rev match:):wub:

Powder coated wheels: completed:)

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They probably put it internally. In doing a VB mod, why would you not do a simple electrical mod to increse the line pressure? It's not there in the OEM setup, it just tricks the tcu into allowing higher pressures.
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Yup. Mine is external because it was the first 2008. VB on 2008 is more like 4EAT than previous 5EAT's. Because of this they had to change the resistor severa times before getting it right. External because they kept swapping. Just a bummer that once they got it right they never put it inside the VB. What if I had mailed it in instead of driving in? Makes me wonder.
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Then it would of sucked for you:p paying for shipping xx times, but how would they know if a diff resistor made it better? That would of sucked:lol:

 

You drove all the way to NJ from CA?

I drove from SC to CA and got of tired/bored from driving on day 4 (last day) I dont think I could of done a round trip

5eat downshift rev match:):wub:

Powder coated wheels: completed:)

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The only advice I can offer is: GIAC USA did a TCU reprogramming for certain Passat 1.8T models, IIRC. Would they be interested in being hired for something like this? I'd pay $200 to be able to adjust my 5EAT with respect to shift speed/points, etc.. I'm sure there's at least another 20-30 people who feel the same way..
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Then it would of sucked for you:p paying for shipping xx times, but how would they know if a diff resistor made it better? That would of sucked:lol:

 

You drove all the way to NJ from CA?

I drove from SC to CA and got of tired/bored from driving on day 4 (last day) I dont think I could of done a round trip

 

 

I am dedicated, but not that dedicated. At the time I was working in NYC and living about 30 miles from IPT. I knew I might get sent back to Cali, so I went to IPT before I had to leave. Made sure to do all my upgrades before the 4k road trip back to Cali.

 

But can you imagine the nightmare if I had shipped it in? They told me they tried SEVERAL resistor values before they got it right. Also took a few extra hours more than normal. I could see it having taken several shipping trips back and forth before getting it right.

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  • 2 weeks later...
Sorry it took a bit. I spaced it. Resistor is 10watt 5.1ohm. Car is 2008 LGT 5EAT.

 

Hope this helps.

 

It helps for me cause mine is 08:)

But doesnt help utc_pyro because his is older model, diff tcu. Its a starting point

 

Do you still have it? can you take a pic and what wire(s) its connected to? I may try it if I can get away not hacking up the harness

 

Hmm...My idea is to remove the wire(s) from the harness plug into tcu, add wire with resistor to the pin end and reattach new wire w/ new pin to harness plug. Thats if the resistor is inline from tcu to VB. If its at the VB then its another story

 

Thanks m sprank

5eat downshift rev match:):wub:

Powder coated wheels: completed:)

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What part of the car did they mount the resistor on BTW? You happen to be able to trace the wires to pins on a connector? Also, if you can touch a multimeter to the leads on it and measure the resistance we can tell how it hooks up to the valve body and how to make it work on the older cars.

 

Thanks M Sprank!

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With it connected. 5.1ohms is really specific, so I doubt it's off much. I want to know what the resistance of the coil plus the resistor together is so I can back out the resistance of the coil mathematically.
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Well, if some one has a contact there familiar with the SSM III tool, I have a few questions that could help us... It's a $3000+ piece of equipment, so I dont think they'll be lending it to us. That said, they could tell us if any updates are avalibel for ANY of the TCU's. If we can find one that has an update, I can get the equipment to "sniff" the flashing of one. That will give us the ROM and how to flash it.

 

I can help you with this if your local dealers are unwilling.

 

There is a 5EAT update for the 05 LGT and OBXT for DTCs, none for 06-07, and there is one for the 08-09 LGT and OBXT for shifting issues. I wouldn't know how to get just those files, but if you have a sniffer program, that might work. However, you would only be able to reflash a TCM with an older Calibration ID, if the TCU that you are trying to flash with the update already has the latest calibration for that TCU, it will not flash it, but you may be able to get the access address.

 

My wife drives an 05 OBXT, I'll see if hers has the latest update.

 

I really need the 4EAT TCU hacked, I've installed a VTD center diff in my 05 FXT, it originally came with a MPT center diff, and the rear speed sensor now reads wrong because of different number of teeth on the sensor wheel. If I was able to procure a donor 4EAT TCU and followed the same steps that you've done in this thread, but in a different thread, would you guys be willing to help or at least point me in the right direction. I have no problem doing the footwork and reading and researching, but I have no background in this kind of stuff, and would most likely need help with the software end of things

 

Also did your class have a textbook? does it have an ISBN number? Or, can anyone recommend a book on assembly language, micro-controller programming? That I could try to wrap my head around.

 

Thanks

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I can help you with this if your local dealers are unwilling.

 

There is a 5EAT update for the 05 LGT and OBXT for DTCs, none for 06-07, and there is one for the 08-09 LGT and OBXT for shifting issues.

Thanks

 

How new (or old) is the update? As in release date or something?

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The update is a few years old as far as I know, and it only pertains to solving a couple TCU codes that the transmission might trigger as a fluke. I don't think it addresses anything else unless there is a second update I am not aware of.
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