P0746 Code - after DSG Service at Dealer

phantom1260

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Aug 15, 2017
Location
Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
My vehicle went into limp mode I believe. It would not go into reverse and was stuck in a single gear going forward.

I had to towed to the dealer and they said they will check to see if it's related to the DSG service I had them perform on Thursday.

I picked up the car after the service on Thursday and Sunday afternoon my wife was gone on an errand when I got a call that the vehicle won't go into reverse. Once I got there I was able to get it into reverse I'm guessing since the transmission had time to cool off while my wife was waiting for me to get there. After I restarted again I lost reverse again.

The gear selection indication on the dash disappears shortly after the vehicle is started. So it will say P when I start and then it'll go away after 3 seconds.
The car was also had the heater core replaced and coolant flushed during the same visit.

I scanned the code and it had a P0746 code. What are the chances they under-filled the DSG during the service? or is it more likely just a coincidence.
The vehicle is at 248,511 Miles (399,940 KM) so anytime I go into the dealership they are quick to blame things on the amount of mileage the vehicle has.

Since I was able to get it into reverse once it had time to cool down I'm thinking it could also be the temp sensor or a loose ground. Would it be all or nothing if it was the mechatronic module or would it be hit or miss as I was able to get it into reverse at least once.
 
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mextdi

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Joined
Dec 16, 2013
Location
Saint Paul, Minnesota
TDI
2006 Jetta TDI 1.9, 2012 Passat TDI SE DSG, Previous 2014 Beetle TDi, 2012 Golf TDi DSG
The solenoid not working properly which is the code you're getting could be normal wear and tear on a transmission or could be a sign of as you say, under-filling. If the car wasn't doing any of these things before it is obvious that the dealership has somehow created them. Could be a loose or broken ground or shoddy workmanship. They have insurance against mistakes performed on vehicles, they just don't like to use it. Call them on the phone and tell them they have to fix it, if they give you trouble you can try calling VW in Canada and explaining the situation, they have muscle. Don't let them bully you into fixing it at your time/expense.
 

phantom1260

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Joined
Aug 15, 2017
Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
Just received a call back from the dealer. They say its the mechatronic unit. There's a leak that's getting into the unit and causing the unit to fail. Their solution is to replace the unit and that will repair the leak as well.

Total $2952.50 CDN

Parts (M- Unit) $2152
Gaskets/Bolts $58
Labor $607.50
Diagnostics Fee $135

They were adamant that it has nothing to do with the service and everything to do with the age and mileage of the vehicle.

I guess I'll be making a call to VW customer care and see what they will do.
 

phantom1260

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Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
Customer care has not been helpful at all. Basically all they do is call the the dealership and then reinforce whatever the dealer explains to them.

I asked to be escalated to a manager. I should expect to receive a call back withing 24-48 hours.
 

phantom1260

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Aug 15, 2017
Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
After looking more into what the Mechatronic unit is. The dealers explanation does not make much sense to me. The mechatronic unit is full of transmission oil where is sits. So how could a leak be feeding into the unit and causing it to fail.

If they said there's a leak and its causing the fluid to be low and the unit to throw an error that would make more sense.

There was no mention of a leak when they did the service or any indication of a leak ever before. So that leads me to believe it was either under-filled or during the service they caused a leak.
 

phantom1260

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Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
While I wait for VW customer care to call me back I've been looking into my options.

I've seen online some are able to test the solenoids in the mechatronic unit and replace the faulty one. Has anyone here done so successfully?

I'm still hoping I can get VW to cover, especially since 2 of the main factors causing this issue can be over filling or under filling the transmission. Perhaps they overfilled it and now that's causing the leak.
 

mextdi

Veteran Member
Joined
Dec 16, 2013
Location
Saint Paul, Minnesota
TDI
2006 Jetta TDI 1.9, 2012 Passat TDI SE DSG, Previous 2014 Beetle TDi, 2012 Golf TDi DSG
I have heard that VW can usually step in and help, and be fair. Sucks they are giving you so much trouble.

You could look into hiring a lawyer and suing the dealership, that is another possibility. Sometimes, the lawyers will only charge their fees if you win. Ask around, someone on here might know a lawyer in your area that can do such kind of work.

On the 01M transmission, the solenoids used to go out and were somewhat easy to replace by replacing the valve body. You have a newer DSG unit which is somewhat different. If you have to replace the valve body on your TDI it should also not be EXTREMELY difficult since the unit faces the front of the car as is somewhat easy to access once the air filter assembly is removed. You can look into getting your valve body reconditioned or purchasing a reconditioned unit as well. You can possibly just replace the faulty solenoid but you'll be kicking yourself if one of the other ones go out shortly thereafter.

Best of luck!
 

phantom1260

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Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
If I replace one of the solenoids do I need to do any reprogramming with VCDS?

I have a meeting with the service manager later on tonight. If that does not go well I will need to consider my options.

First I'll need to confirm the fluid level is correct. Then check the grounds and wiring for any shorts. If that does not help then I'll be taking the mechatronic apart and testing the solenoids.
 

phantom1260

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Joined
Aug 15, 2017
Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
I just replied to another thread where someone had a similar issue but wanted to update this thread as well.

Just got back from the dealer and as per the pictures they provided I have a leak in the Mechatronic unit connector as well.

They cleaned it up and reconnected it but on my way home from the dealer the transmission faulted out again and I was limited to 1 gear.

No error code yet this time but before I went to the dealer I pulled Code P0746. They provided me with the code P1814 at the dealership.

Any idea if there is any way to stop this leak or is my only option a new Mechatronic Unit?




 

phantom1260

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Aug 15, 2017
Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
After some more research last night I've read that there are 2 o-rings behind the mechatronic cover on the connector. Some have had luck with replacing those two o-rings and the cover gasket to stop the leak.

I will have to drain the new DSG fluid and replace it again. I guess I don't have to change the filter though. If there's enough space to test the solenoids without taking the mechatronic offf I will try to check the resistance as well while the cover is off.

I've added some pictures that depict the mentioned o-rings.




 

mextdi

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Joined
Dec 16, 2013
Location
Saint Paul, Minnesota
TDI
2006 Jetta TDI 1.9, 2012 Passat TDI SE DSG, Previous 2014 Beetle TDi, 2012 Golf TDi DSG
If just replacing the seal and the o-ring do the trick, then you'd be golden! However, be advised that the amount of fluid in and around the connector must have had some sort of consequence. I am not sure if the DSG fluid conducts electricity but I am thinking it can easily short things out, confuse the computer, etc. It is not good at all. Before you continue with repairs on your own, fight for your rights as a paying customer. If you do the repairs and then maybe get a reply, at most you will receive compensation for parts used, definitely not loss of vehicle use and time.

If you continue with the repairs on your own, I would advise to buy a brand name contact cleaner and clean and DRY very well both connectors before attempting to reconnect them. You will probably not need to replace the filter unless you introduce dirt and such into the oil or the system. I am sure when you remove the cover you will do this so probably a good idea to replace the filter as well. Try first to replace the o-ring by the connector, then clean, run and test. If you are still having a leak, then the cover would be an idea but the o-ring seems to be directly responsible for the leak into the connector itself.

Best of luck!
 

phantom1260

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Aug 15, 2017
Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
I've gathered all the parts and tools I need for the job. Hoping to find some time this weekend to tackle it.

I just need to source 2 more jack stands in order to lift the vehicle level from all 4 corners.
 

phantom1260

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Location
Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
I was able to open up the Mechatronic cover this Sunday and replace the O-rings. After it was all done the vehicle still had the same symptoms. Once it got up to temperature the I lost reverse and only had a single gear forward.

I also replaced the fluid and I think I may have under filled it. When I went to drain it after the transmission fluid reached 35 degrees I only had a small trickle drain out.

I also tested all of the solenoids and none of them seemed to have a bad reading.

Next steps:

I'm going to try to put in another liter of fluid and drain the excess again to make sure I got the level correct. I did not do the basic settings either so after I check the fluid level I can try that to see if it helps.

Since it only happens once the transmission fluid is up to temperature I would think its not a wiring issue. There was quite a bit of fluid leaked all over the place. I think what happened was the transmission was fine the first couple of days after the service at the dealer and then because of the leak once enough fluid leaked out it started to give the error for the pressure control valve N215 since the fluid went to low.
 

phantom1260

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Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
I redid the DSG fluid today. Put in another litre and drained the excess once it got up to 35 degrees.

Did not seem to help. Once the car gets up to temperature it losses reverse and only 1 gear forward.

I ohm tested the N215 solenoid along with all the others last week and it was fine. Perhaps it was not completely bad but has an intermittent fault. I'm hesitant to change out the N215 solenoid since the resistance was okay on it. I don't want to spend money on the solenoid if it's not the problem.

One thing I haven't checked is the grounds. I'll see if I can check that tomorrow. I'm having a hard time believing the oil in the connector is the issue.


Considering looking for a used transmission and swapping it in instead of paying $1500-$2500 for a new Mechatronic.
 

Ol'Rattler

Top Post Dawg
Joined
Jul 3, 2007
Location
PNA
TDI
2006 BRM Jetta
A really great reason to never own a VW with a DSG transmission. If my wife couldn't drive a manual, she can walk every where she goes if she does not have her own car. Her auotragic Toyota's certainly keep the piece in my house. If you own a VW, an automated transmission (DSG or auto) is a very bad and expensive idea.
 

phantom1260

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Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
I've found someone locally selling the solenoids for $50 a piece. At that price I guess it's worth a shot to see if it will fix the issue before swapping in a new DSG.
 

phantom1260

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Location
Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
Previously the error was not permanent. It only showed up after the vehicle warmed up to a certain temperature. Now before I changed the solenoid it was the error would not clear and would come back instantly.

After I changed the solenoid it again would not clear and would come back right away. I was waiting for the oil to heat up before I drained the excess and I periodically kept trying to reset the code and at one point it cleared. It stayed cleared for maybe 10 mins. I was going through the scanner and saw a bunch of error codes attached below. When I cleared these codes the transmission error came back. Not sure if it was coincidence or if the oil reached the temperature where it usually errors out.

I did also finally clean the ground wire on under the airbox. I'll have another look to see if there are any other grounds that need to be cleaned. With all the other electrical errors would it make more sense for it to be a ground issue?

My DMF has been noisy as well for quite some time but I doubt that would be causing this error.

Looks like maybe a used transmission is the best option forward.








 
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phantom1260

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Aug 15, 2017
Location
Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
looks like the the TMU (Transmission Mechatronic Unit) is now a covered part under the TDI warranty for 2009 models.

In the case of certain Model Year 2009 and 2010 vehicles, this
approved emissions modification cannot be applied without additional
steps. For these certain Model Year 2009 vehicles, the Transmission
Mechatronic Unit (TMU) – the component that houses the device that
controls the vehicle’s automatic transmission – must be replaced in
order for the vehicle to receive the emissions modification. For these
certain Model Year 2010 vehicles, they require additional hardware
updates as part of the emissions modification. Not all Model Year
2009 and 2010 Volkswagen 2.0L TDI vehicles are impacted by these
additional steps.
When I had the fix completed the TMU was not a part of it at all. I wonder what my chances are if I bring this up to the dealer.

TDI
Extended Emissions Warranty Information
 

phantom1260

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Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
So I was able to find another Jetta with the matching transmission code. I've put down a deposit and will be going to pick it up on the weekend.

Current owner says it has a DPF issue and is in limp mode.

I'm hoping I'll be able to swap the transmission into my Jetta and have it back on the road.
 

phantom1260

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Joined
Aug 15, 2017
Location
Brampton, Ontario
TDI
1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
Finally got some time to do the swap. While removing the transmission from my car I noticed a frayed wire. Turns out its from the coolant heater plug. Not sure if this wire would be causing any short to ground issues. Isn't this wire only live when the heater is plugged in?

Going to either remove it or repair it either way. Just wondering if this was contributing to the electrical errors all along.

Right now I have both the transmissions removed. Just dealing with a stuck pilot bearing. Once that's out I'll be putting in the new flywheel from rockauto and the donor transmission from the other car.
 

Jeffro420

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May 20, 2017
Location
Raleigh, NC
TDI
2010 Jetta TDI
Finally got some time to do the swap. While removing the transmission from my car I noticed a frayed wire. Turns out its from the coolant heater plug. Not sure if this wire would be causing any short to ground issues. Isn't this wire only live when the heater is plugged in?

Going to either remove it or repair it either way. Just wondering if this was contributing to the electrical errors all along.

Right now I have both the transmissions removed. Just dealing with a stuck pilot bearing. Once that's out I'll be putting in the new flywheel from rockauto and the donor transmission from the other car.
Hey phantom1260! Wow, my 2010 Jetta TDI is going through the EXACT same issues you are having! My DMF was also noisy for some time before these issues finally arose, and I discovered DSG fluid leaking from the DSG box while I was changing my engine oil.

For me, this all culminated when I lost power completely (luckily while exiting the highway) - it was like I was in neutral even though I was in gear. Tried to limp it a bit to get back to the mechanic but she suddenly revved to an extremely high RPM while trying to shift out of first, so I coasted to a stop and got towed to the mechanic. But reading through your post was extremely helpful, as the mechanic has explored all of these same issues with my car.

Question for you - did the transmission replacement work to resolve the issue? After extensive troubleshooting that's what my mechanic (not the dealer) has proposed to fix the problems. I don't have the mechanical inclination or the time to do the work myself (with my 2 kids being 18 months old and 2 weeks old), but if it worked for you then hopefully I can have more confidence going this route.

Please update! Thanks!
 

phantom1260

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Brampton, Ontario
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1997 Jetta GL IDI, 2010 Jetta TDI (Sold)
Well my swap didn't exactly go as planned and is still pending so can't tell you for sure if it will fix your problem.

While I was doing the swap I had the donor transmission into my car and was just bolting everything up, When some of the bolts were kind of tight. At this point I should have noticed something was wrong but I continued to tighten them with increasing force.

Turns out something wasn't aligned right and the transmission wasn't set properly against the engine yet. The the excessive force I ended up breaking a piece off the transmission housing and the engine oil pan.

So right now I have the transmission back out. I'll going to see if I can get the broken piece weeded back on for the transmission. For the the oil pan I think I'll just remove the oil pan from the donor car and replace it with that.
 

backfast61

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Mechanicsville , VA
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2006 VW Jetta TDI automatic,2006 VW Jetta TDI 5 speed
Well my swap didn't exactly go as planned and is still pending so can't tell you for sure if it will fix your problem.

While I was doing the swap I had the donor transmission into my car and was just bolting everything up, When some of the bolts were kind of tight. At this point I should have noticed something was wrong but I continued to tighten them with increasing force.

Turns out something wasn't aligned right and the transmission wasn't set properly against the engine yet. The the excessive force I ended up break
 

backfast61

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2006 VW Jetta TDI automatic,2006 VW Jetta TDI 5 speed
Sorry to read about things not going to well.
I have 2006 vw Jettas with automatic dsg transmissions for each of my kids.
After having the same issue with one of them.. I had to bite the bullet and buy a brand new mechatronics from the dealership. It's programmed from the factory and is a pretty simple install . The 14 year old mechatronics gets old and brittle after being in the transmission. It is going to leak oil into the unit especially when transmission is not serviced at proper intervals. My dealership matched the price of an online dealership and it wasn't that high .
I do all of my own maintenance and repair so I only had parts cost.
 
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