DiogoBett

Hey guys. I've been having problems with my transmission 722.9 PLUS (7-speed automatic), rough gear shifts (upwards only) and randomly (you can drive well for an entire week and then...) you hear a loud bang (transmission disengages) and the PRND symbols disappear from the Instrument Cluster leaving you in LIMP mode.
There is no "Check Engine" light even though there are error codes (I'll show you guys in a bit) and if you turn off the ignition, remove the key and wait 10 seconds the PRND symbols will appear again and the car will work as normal for a few more minutes. Due to this being random, it's likely an electrical issue.

When I started having this problem out of the sudden I decided to go do a transmission oil change - It went well - Followed WIS procedure - Car started drove as normal and then randomly... Same problem.
• Transmission: 722.966 (PLUS)
• Transmission Oil Type: Blue (9L)
• Certification: MB 236.15
• Kit: Meyle 0141371107

I've checked the wiring going from the TCM module (Which is a VGS3, I can communicate with it without any problems using Xentry) and all seems good and secure, cleaned them a bit and covered a few exposed wires... Issue still happening.

All the error codes from Xentry (After clearing them and letting the issue happen again randomly):
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• Module: N3/9 - Motor electronics 'CDID3' for combustion engine 'OM651' (CDI)
• Fault(s): U010187 Communication with control unit "Transmission" has a malfunction. The message is missing.
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• Module: N62 - Parking system (PTS)
• Fault(s): C44700 Implausible data were received from the central gateway. / C10100 Communication with control unit "Transmission" has a malfunction
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• Module: N30/4 - Electronic stability program (ESP®)
• Fault(s): C257200 No CAN message was received from control unit 'Combustion engine' or 'Transmission'. / C322000 No CAN message was received from control unit 'Transmission'. / C258600 No CAN message was received from control unit 'Combustion engine' or 'Transmission'.
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• Module: A1 - Instrument cluster (IC)​​​​​​​
• Fault(s): U010100 Communication with control unit "Transmission" has a malfunction.
​​​​​​​----------​​​​​​​​​​​​​​

Any help is appreciated, I'm suspecting the problem is the CANs (Voltage Inverter, Distributor Blocks, etc.), there was no water damage...

JettaRed

iTrader: (1)

The behavior of turning the car off and then on and it's back to normal for a while sounds like a conductor plate problem. It's interesting that you don't have any transmission codes from the TCU.

Odd Piggy

Has the interior of the car ever been wet? All those communication errors may be coming from a corroding canbus terminal.

DiogoBett

It was my first thought, but since it's one of the newest versions (VGS3) and I can read the all the 3 sensors on it without any issue... It's not it (I think).

DiogoBett

I've lifted the passenger side carpet (where a lot of wiring is) and it was dry, not humid at all. But I still haven't checked the driver side.

JettaRed

iTrader: (1)

Well, the powering off and on is resetting something. I agree, you should see a TCU error.

You might want to run through the tests in XENTRY for each of those controllers.

DiogoBett

I've done a few tests and resets on the controllers that reported errors. Car is driving worse due to shift and torque converter reset.

VGS still shows no faults, but I've noticed low voltage.


Also here's the low voltage:

JettaRed

iTrader: (1)

I know these cars are temperamental when it comes to voltage supply, but I wouldn't think being off by 0.3V would cause these problems. Was the engine running when you hooked up XENTRY?

DiogoBett

Engine was off that's why battery was 12.2V (Like in the image), but when driving it's usually between 13V and 14V due to alternator.

I'm completely at a loss of what the issue is... I've got to check the CANs under the driver seat this weekend.