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Discussion Starter #1 (Edited)
My 2007 B200 is showing the "Visit Transmission Workshop" and is not driving right when warm. I have looked around and most people say it's the speed sensor. Is the consensus?

I can send the TCU out to a shop and they will 'rebuild' it for around $300. Is there anyway I can fix it myself? Can I ge the part the repair shop gets and is it a matter of soldering a new one onto the board?

I hate to give money out to a shop if I can fix the unit myself.

Thanks,
Ian
 

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B170 (W245) - Year 2008
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First things first, it can be done, but it's not a job for faint hearted ones. you need some tools to perform this job.

1. Xentry DAS is a must have. This will help you clear errors in the control module. Else TCU will continue misbehaving even after repair.
2. You need a special tool to open up the TCU cover. This is one of the biggest hundle you will meet. Once you have opened the cover.
3. You will also need non lead based soldering wire and flux.
3. Locate the four speed sensor wires (pin 1 ground, pin 2 power, pin 3 b4 speed sensor, pin 4 b5 speed sensor)
4. Out of the four wires, check the one with loose connection. Scratch it to remove aluminium coating, put some solder.
5. Scratch the base terminal and also put some solder. Now connect the wire with the terminal.

Remember you will fight some gel in there and soldering the joint is a nightmare. Wish you success.
Attached are some pictures from an old TCU I tried repairing.
Good luck.


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2006 B 200 .....& Audi A6..
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That certainly looks like a messy piece of equipment to get at....Good Luck with this repair and take a few photos for us here as the repair progresses......!!

Want to see how ugly it is to get that cover off..(from the guy who has a manual transmission here..)

Thanks>>>>>>>>>
 

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Discussion Starter #9
First things first, it can be done, but it's not a job for faint hearted ones. you need some tools to perform this job.

1. Xentry DAS is a must have. This will help you clear errors in the control module. Else TCU will continue misbehaving even after repair.
2. You need a special tool to open up the TCU cover. This is one of the biggest hundle you will meet. Once you have opened the cover.
3. You will also need non lead based soldering wire and flux.
3. Locate the four speed sensor wires (pin 1 ground, pin 2 power, pin 3 b4 speed sensor, pin 4 b5 speed sensor)
4. Out of the four wires, check the one with loose connection. Scratch it to remove aluminium coating, put some solder.
5. Scratch the base terminal and also put some solder. Now connect the wire with the terminal.

Remember you will fight some gel in there and soldering the joint is a nightmare. Wish you success.
Attached are some pictures from an old TCU I tried repairing.
Good luck.


Sent from my Nokia 6.1 Plus using Tapatalk
Thanks Fredrick, great pics. When the TCU is sent to a repair shop and they charge $300, is this what they do? I have no problem doing this, I have done far more intricate work. As far as Xentry DAS goes, I know it's software, but can it be done through a computer with a cable, or does it need to be a specific programmer? Can I bring it to Mercedes after the repair, is it a simple programming procedure?
 

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B170 (W245) - Year 2008
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So, they charge 300$ for that job. Also Xentry is a software but you will need a passthru device to enable you communicate with the vehicle. Although I guess any device with access to OBD protocol would do the job.

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So, they charge 300$ for that job. Also Xentry is a software but you will need a passthru device to enable you communicate with the vehicle. Although I guess any device with access to OBD protocol would do the job.

Sent from my Nokia 6.1 Plus using Tapatalk
could it be possible? can you connect the car by a cheap obd over xentry software?
 

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B170 (W245) - Year 2008
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Buy a cheap DXDiag nano tool, costs approx 80usd. Then you download Xentry PassThru version.

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W123 '83 200, W210 '98 E200K, W212 '13 E350
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What causes the issue? Temperature, car aging or something else? Why now and not at the eariler stage of the car ownership?
Vibration and heat and cooling cycles over time. I used to have an '86 Mazda RX-7. They tended to have many issues with cold solder joints over time. Small CPU that controlled warning chime, horn, flashers. Idiot light cluster (separate from the gauges on those cars) and clock. I became quite good at soldering. And the work above doesn't look good.
 

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2006 B 200 .....& Audi A6..
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Thanks Paulo, but could you explain more on "And the work above doesn't look good " ..quoting you here..?
 

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Discussion Starter #18
2. You need a special tool to open up the TCU cover. This is one of the biggest hundle you will meet. Once you have opened the cover.
Where do I get this tool, or where can I see a picture of it so I can see how it works? I looked arounf the netbut without any point of reference, it's almost impossible to find it.

Thanks,
Ian
 

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W123 '83 200, W210 '98 E200K, W212 '13 E350
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Thanks Paulo, but could you explain more on "And the work above doesn't look good " ..quoting you here..?
Oh boy. I didn't want to sound critical. But the soldering didn't seem very neat, it looked like the solder was resting on the board instead of seeped into the solder pads (insufficient flux maybe), and that soldering iron seemed like it was a little high in wattage (power). But that also depends on the user. You just have to be careful not to overheat components.

Having said that, I'm far from an expert.

/change topic

I find it interesting where the soldering was taking place. I thought the issues were only with the soldering of the speed sensors to the board becoming bad (due to them being the only thing that holds the sensors AFAIK). I've said before that I haven't really looked into the TCU repairs too much. It's pretty obvious.

I was also surprised to see 'wires' soldered like bridges across the board, which looks to be factory.
 

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Discussion Starter #20
I opened the TCU and I see some liquid above the area where the speed sensor wires are. Is this an indication of a problem? Is this from overheating at that spot?

As for resealing it, polyurethane sealant should do the trick
IMG_20191210_155309636.jpg
 
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