P1648-vw -

I can help identify the most likely culprit and direct you to the specific module to check. VW P1648 Code: Troubleshooting and Solutions | JustAnswer

Check for accompanying codes like P1626 (missing message from TCM) or ABS/TC-related codes. p1648-vw

Broken, shorted, or corroded wiring in the powertrain CAN bus network. I can help identify the most likely culprit

Verify the ECM and TCM are receiving proper voltage and have good grounds. p1648-vw

If water ingress is minor, cleaning the connections and drying the module can solve the issue, though the water leak (usually clogged sunroof drains) must be fixed.