VW Transporter Water Sensor Fault Causing Engine Issues

I faced a very similar issue with my VW Multivan from 2010. Being somewhat experienced with VW electrical faults, I recognized those symptoms immediately, rough running and check engine light combined with moisture sensor problems. The car diagnostics revealed a faulty connection between the water sensor and the ECU. The electrical fault was causing erratic readings, making the engine run rough especially during the warm-up phase. The sensor itself was actually fine, but the cable connection had corroded over time. My trusted workshop found that the plug connection to the moisture sensor was damaged, likely due to water exposure over the years. They cleaned the connections, replaced the damaged wiring section, and properly sealed it. Total cost was 95€ for parts and labor. The repair completely resolved the rough running issues and the check engine light hasn't returned since. The sensor fault codes cleared up immediately after the fix. Could you share: Your engine type (TSI, TDI)? Does the rough running occur more during cold or wet weather? Have you noticed any correlation between the sensor fault and specific driving conditions? This would help determine if your issue matches what I experienced with my vehicle.

Had my last service 2 months ago at 33701km. The rough running issue turned out to be more complex than initially thought. After running car diagnostics, they found the moisture sensor was only part of the problem. The main culprit was actually a corroded wiring harness leading to multiple sensor fault codes. The mechanic discovered water had been seeping into the connector housing, causing intermittent malfunction indicator signals. They ended up replacing the entire sensor assembly and surrounding wiring for 280€. The car runs perfectly now, no more check engine light or rough running. The repair also resolved a minor hesitation I noticed but hadn't mentioned in my original post. Would definitely suggest checking the wiring connections first before replacing any sensors. Often the car sensor itself is fine, but the electrical connections are the real source of trouble.

This matches exactly what I experienced with my VW Multivan. Water infiltration and corrosion issues around sensors are quite common in these models, and your repair approach was spot on. After fixing my initial moisture sensor connection issue, I also discovered some related wiring problems about 6 months later. The malfunction indicator kept triggering intermittently because water had damaged more of the wiring harness than initially visible during the first repair. The complete wiring harness replacement I eventually got was more expensive at 310€, but it solved all sensor testing issues permanently. Looking back, this would have been more cost-effective than my initial partial repair. The key learning from both our cases is that auto electronics issues often extend beyond the obvious sensor fault. When moisture gets into one area, it typically affects surrounding components too. Having the mechanic thoroughly inspect all nearby wiring and connections during sensor repairs can prevent repeated workshop visits. Have you noticed any changes in how the engine performs in wet weather since the repair? My Multivan used to show slight hesitation during rainy conditions, but that completely disappeared after the wiring harness replacement.

Thanks for sharing the repair details. My engine is a 2.0 TDI and yes, the rough running definitely gets worse in cold and wet conditions. Since discussing this issue, I did some additional sensor testing this weekend and found something interesting. The electrical fault seems to get worse after the car sits overnight in humid weather. My onboard diagnostics showed multiple sensor issue codes this morning, all pointing to the same wiring area you mentioned. The malfunction indicator appears more frequently during these conditions. Based on your experience and repair costs, I think I will have the entire wiring harness checked and possibly replaced rather than just fixing individual sensors. The 280€ price you mentioned seems reasonable considering the comprehensive nature of the repair. The correlation with wet weather is exactly as you described. When driving in rain, the engine hesitation becomes more noticeable, suggesting water is indeed getting into the connections. This matches the car diagnostics report showing moisture-related electrical faults. I will schedule a repair next week and update once completed. Your input helped confirm this is a known issue with a proven solution rather than just a unusual sensor fault.