I believe many Volkswagen Passat owners must have come across with this trouble code on their car before as this seems like a pretty common fault on this particular model due to a very poor design of Volkswagen when it comes to locating their Transmission Control Module (TCM).
I got passed on a Passat with the same trouble code a while ago by a workshop who had already replaced a Transmission Range Sensor/ or the neutral switch on the same car but the issue still exists, gear stucked on high, after restarting the car, gear appeared normal, when I moved the shifter from P to R to N all working fine, when I move the shifter to D, gear lights on the dash display didn't light up on D, if I move shifter to tiptronic, no display for tiptronic gear selection. Continue moving to 4 is fine, but once I moved to 3, all gears display lit up, gear got stucked on high gear again.
And similar to other Passat with the same issue, when I opened the floor carpet on the driver side (front right), the carpet was soaky wet. I have searched through the internet and followed others suggestions checking the splice joints etc to no availability. I couldn't find any corrosion on the joints nor any broken wiring. I even suspected that it might be a faulty new Transmission Range Sensor hence I performed resistance check on the sensor itself, opened TCM to inspect and ensure there is no sign of water damage on the module, removed center console to checked gear shifter magnet but all seems to be in good shape. At the end, I found a page with reference voltage of each gears, it was identical to my result when I performed voltage check on the 4 wires coming out of pins 2, 3, 4 and 5 on the Transmission Range Sensor to pins 8, 9, 36 and 37 on the TCM, apart from the green/ white wire, from pin 3 on TRS to pin 8 on TCM, I was getting close to 5V when I shifted the gear to D and 3, when I supposed to get 0V. (See piucture)
At this point I was thinking that might be something shorted internally inside the TCM. But when I did the same test with the TCM unplugged, I got the same test result. I started cutting open the wiring loom to look for burnt, melt, corroded wiring but everything appeared to be in working order. At last, I cut the wire down to 4 to 5cm off the TCM plug to isolate the rest of the wire in the loom, but the result still the same! I am still getting near 5V on the same wire when gear shifted to D and 3. So I carefully inspected the TCM plug, it looked so normal and nothing suspicious at all. Not until I pry opened the connector plug, I spotted a tiny bit of burnt mark on pins 8 and 9 of the connector plug. I nearly missed it if I didn't check it slowly and closely. And this was the culprit! (See pictures)
So, after replaced with a used plug from VW wrecker and a good few hours of re-wiring I managed to get the problem solved! I hope this page can help others to solve the same problem as it is not always the neutral switch that trigger this trouble code. And thanks to all the good people who are willing to share their solutions on forums such as: