Rough Idle + Check Engine: Moisture Sensor Mystery Solved

Faced the same issue with my 2008 Chevy Uplander last winter. The moisture sensor malfunction turned out to be just a symptom, not the root cause. After proper sensor testing, we discovered corroded wiring connectors feeding into the main electrical harness, a pretty serious auto electronics issue that was causing multiple sensor misreadings. The fix involved replacing the damaged wiring section and installing new weather-sealed connectors. The original moisture sensor was actually fine, it was just getting incorrect voltage due to the bad connection. Once fixed, both the rough running and check engine light cleared up completely. Worth checking your wiring harness near the firewall where moisture tends to collect. Water intrusion in that area can cause similar electrical fault symptoms. The car sensor readings might look bad on diagnostics, but the actual sensors could be perfectly good. My advice: have someone specifically check the wiring connections before replacing any sensors. These electrical gremlins can be tricky, but it's usually more about connection issues than failed components.

Yeah, had a nearly identical problem with my Astro last year. Started with the check engine light, followed by rough running, and then the mechanic went on about moisture sensors too. The malfunction indicator kept coming on even after they replaced the sensor. Turned out the real culprit was corrosion in the main wiring harness, not the water sensor itself. Got it fixed about 8 months ago and it's been running smooth since. What did the total repair cost come out to for you? And have you noticed any other electrical issues popping up since the fix? In my case, the bill wasn't pretty, but at least the problem hasn't returned.

Got an update on my Uplander repair situation. Finally got it properly diagnosed, definitely the water sensor malfunction was causing those issues. Just like you figured, the sensor itself wasn't bad. The mechanic found a faulty cable connection at the sensor plug that was causing weird readings and the rough running. Total repair came to 95€ for fixing that connection issue. Pretty reasonable considering all the trouble it was causing. Since the repair, the car's running perfectly, no more check engine light, no rough running, nothing. The car diagnostics are all clean now. Looking back, the electrical fault symptoms really had me worried it might be something major, but turned out to be just that one bad connection throwing everything off. No other electrical issues have shown up since the fix, everything's working like it should. These sensor issues can be deceptive, but once you get the right diagnosis, the fix isn't always as complicated as it seems.

Thanks for asking about the repair cost. I finally took it to a different shop last week. The mechanic did thorough car diagnostics and found serious corrosion in the wiring harness, just like you mentioned. All those moisture sensor readings were wrong because of bad connections. Total bill came to €385, €150 for diagnosis and electrical fault testing, plus €235 for replacing the damaged wiring section and installing weatherproof connectors. Pricey, but worth it since the malfunction indicator hasn't come back on. Engine's running smooth now. Had them do extra sensor testing while they were at it, all the sensors were actually fine, just getting wrong readings from the bad wiring. No other electrical issues since the repair. The first shop wanted to replace multiple sensors which would've cost way more and probably wouldn't have fixed anything. Lesson learned, always get a second opinion when dealing with tricky electrical problems. My new mechanic actually showed me the corroded wiring they removed, so I know exactly what I paid for.