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Pete
Pete, Automotive Mechanic
Category: Transmissions
Satisfied Customers: 29037
Experience:  GM and Mercedes vehicle technician.17 years experience.
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I'm having shifting problems with my Passat. The tranny

Customer Question

Hi I'm having shifting problems with my Passat. The tranny is in some kind of limp mode. The gear selector on the dash is out as well. Engine runs fine
Submitted: 1 year ago.
Category: Transmissions
Customer: replied 1 year ago.
I pulled codes with my vcds scanner. Following codes are, p1626 missing msg from TCU, p1830 pressure control valve 4 short to plus, p1820 pressure control valve 2 short to plus, p0706 transmission range sensor, p1750 supply voltage low because battery went dead and p1747 transmission power solenoid open or short to ground. I'm kinda thinking bad TCU?
Expert:  Pete replied 1 year ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

The first thing that needs done is to have the fault codes cleared out then operate the vehicle and see if it either operates properly as in some cases when the battery has low voltage it can set fault codes needing cleared out to correct an issue like this or to see which codes come back first.Once this is done the code can be diagnosed to locate and repair the fault here.

It is possible the TCU is the cause as this can be common or a wiring issue to the TCU or transmission needing located and repaired.If you can clear the codes then operate the vehicle and let me know which codes come back this will help.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 1 year ago.
Ok I will clear codes and see what comes back
Expert:  Pete replied 1 year ago.

O.k.,let me know what comes back when your ready.

Thanks Pete

Customer: replied 1 year ago.
Ok got the car back in the shop and cant communicate with the PCM or TCU. Checked fuses and checked power and ground at dlc connector. I wonder if something is getting worse
Expert:  Pete replied 1 year ago.

This can be an internal electrical fault in the TCU causing the no communication issues with both the TCU and PCM as the data lines are communicating with each other if the TCU fails internally it will cause the issues here especially since you did have codes for TCU communication issues already.

The other causes is a wiring fault at or leading to the TCU needing repaired.If you have not checked the wiring at or leading to the TCU this needs done and if a fault is found it will need repaired but if no wiring issues are found then I suspect the TCU needs replaced.

Thanks Pete

Customer: replied 1 year ago.
Ok that's what I was starting to think. Where is the TCU on this car? And what color wires should I be checking?
Expert:  Pete replied 1 year ago.

The TCU is located under the carpet on the passenger front side of the vehicle.You have to peel back the carpet to access it.You will want to check all wiring and wiring connections at the TCU and leading to it for any corrosion or damage needing corrected.

https://www.dropbox.com/s/7k3bo2nf63eivd3/tcm-01-19.gif?dl=0

Let me know if you need anything else and feel free to rate my help.

Thanks Pete

Customer: replied 1 year ago.
Just found out the sunroof was leaking in a bunch of water the car has been sitting for About 3 months and there is a brick of ice on the passenger floor probably by the TCU
Expert:  Pete replied 1 year ago.

Most likely the TCU is damaged as well as the wiring connections to it.Unplug the TCU and see if the terminals or wiring is corroded at all.If it is then the terminals will need cleaned or replaced and the TCU replaced to correct this issue here.The location of the leak needs found as well and repaired so this doesnt occur again.

Thanks Pete

Customer: replied 1 year ago.
Ok the module had water in it as well as the connector. So I'm looking for another one. Mine is (8DO 927 156 AN) and the one I found is (8DO 927 156 BM). I was wondering if that will work?
Expert:  Pete replied 1 year ago.

I recommend using the part number that is on your module as some are different and can cause issues.You can contact a dealers parts department and they can look up the part number and cross reference it to see if any other part numbers will fit and work on your model here.One place I use for used parts is http://www.car-part.com and you might be able to find the correct part number from there.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Thanks Pete