VW Caddy Engine Light + Rough Running: Moisture Sensor Fix

Faced a comparable sensor issue on my 2007 VW Touran diesel at 145000km. The engine light flashing combined with rough running often points to a water sensor malfunction in the fuel system. The electrical fault turned out to be more than just a faulty sensor. The entire wiring harness connecting the water sensor to the engine control unit had corroded due to fuel seepage. This is a known weak point in these engines. The auto electronics needed a complete rewiring of that section, plus replacement of the actual sensor unit. The repair required: Full diagnosis of the sensor circuit, Removal of fuel filter housing, Replacement of corroded wiring harness, New water sensor installation, Computer reset to clear fault codes This was a serious repair that took nearly a full day at the shop. If left unaddressed, water contamination in fuel can cause major engine damage. The car sensor symptoms you describe match exactly what happened with my Touran before the repair. Would strongly recommend getting this fixed by a VW specialist who understands these specific sensor issues, rather than a general repair shop. The proper diagnosis of auto electronics is crucial for this repair.

Thanks for sharing your experience. Having the same moisture sensor fault on my 2005 Caddy. The electrical fault symptoms match exactly what you described. Got it fixed last month and the engine runs smooth now. Did the repair cost stay around what they quoted initially? My total bill came to 580€ for parts and labor. Also curious if you had any other sensor issues pop up since getting it fixed? The mechanic mentioned the fuel pressure sensor might need checking soon due to its age.

Just wanted to follow up and share that I had a much simpler fix than my initial repair story suggested. After seeing a certified mechanic, the water sensor malfunction turned out to be just a loose connection. The repair only cost 95€ to fix the faulty plug connection at the sensor. Much better outcome than my previous experience with the Touran where extensive rewiring was needed. No additional sensor issues have appeared since the repair. The auto electronics are working perfectly and the engine runs smoothly. For reference, your 580€ bill suggests they might have replaced more components than necessary. A basic sensor testing procedure should have identified the loose connection first before replacing parts. When dealing with car sensor problems, always worth getting a second opinion if the quote seems high. The fuel pressure sensor they mentioned is a separate system. Unless its showing actual fault codes, I would not preemptively replace it just based on age.

Thanks for the helpful input. Let me share how my repair went. After getting multiple quotes, I took it to a certified VW shop that specializes in auto electronics. Smart move as it turned out. The mechanic found that the moisture sensor fault was actually caused by a damaged wiring harness, similar to what others mentioned. The electrical fault also affected some nearby connections. They fixed all the corroded wires and replaced the sensor unit. Total repair took about 4 hours and cost 580€, which included: Complete car sensor diagnostic, New wiring harness, Replacement moisture sensor, Labor costs Money well spent considering the engine runs perfectly now. No rough running or warning lights since the fix. I skipped their suggestion about the fuel pressure sensor check since it shows no current issues. Looking back, going to a shop that really understands these sensor systems made a huge difference. No more hesitation about getting electrical issues fixed properly.