12639277 WATER IN FUEL SENSOR FOR 2001-2011 DURAMAX 6.6L SILVERADO/SIERRA

iFJF part No.: FJ-FSS01-WH. 12639277 Water in Fuel (WIF) Sensor for Duramax 6.6L Diesel (2001-2011) The 12639277 Water in Fuel Indicator Sensor is a critical safety component for your Duramax 6.6L diesel engine. This sensor continuously monitors the fuel supply for water contamination and alerts you via the dashboard "Water in Fuel" warning lamp before water reaches your expensive fuel injectors . Water in diesel fuel can cause catastrophic injector failure, fuel system corrosion, and microbial growth (diesel bug) this simple sensor is your first and only line of defense. Compatible with 2001-2011 Chevrolet Silverado and GMC Sierra trucks equipped with the Duramax 6.6L turbo diesel (LB7, LLY, LBZ, LMM), our aftermarket replacement offers OEM-grade reliability at a fraction of dealer pricing. If your "Water in Fuel" light stays on after draining the filter housing or never comes on at all your sensor has likely failed. Key Features 8-Sided Hex Design: Improved over the OEM 6-sided design easier to grip with a wrench, less likely to round off during installation and removal Direct OEM Replacement: Replaces GM 12639277, 12639450, 97384931 plug-and-play with factory wiring harness connector Water Detection Circuit: Uses conductivity-based detection when water (conductive) bridges the sensor electrodes, the circuit completes and triggers the dashboard warning Pre-Installed Viton O-Ring: Diesel-rated seal prevents leaks at the filter housing interface Corrosion-Resistant Probe: Stainless steel electrodes resist pitting and false triggering from fuel contaminants Vehicle Compatibility Make Model Year Range Engine Chevrolet Silverado 2500HD / 3500HD 2001-2011 6.6L Duramax (LB7, LLY, LBZ, LMM) GMC Sierra 2500HD / 3500HD 2001-2011 6.6L Duramax (LB7, LLY, LBZ, LMM) Chevrolet Express 2500/3500 Van 2006-2011 6.6L Duramax LMM GMC Savana 2500/3500 Van 2006-2011 6.6L Duramax LMM Technical Specifications Specification Value OEM Part Numbers 12639277, 12639450, 97384931 Sensor Type Conductivity (resistive) Connector Type 2-pin weather-sealed (matches factory harness) Thread Size OEM-spec direct fit into filter housing port Hex Size 8-sided (improved grip over OEM 6-sided) SKU FJ-FSS01-WH FAQ Q: How do I know if my WIF sensor is bad? A: Common failure symptoms: (1) "Water in Fuel" light stays on constantly even after draining the filter housing completely; (2) Light never comes on even when you know there's water in the system (no self-test at key-on); (3) Light flickers intermittently corroded or loose connector; (4) Diagnostic trouble code P2264 (Water in Fuel Sensor Circuit). Q: Can I clean my old WIF sensor instead of replacing it? A: Sometimes. Remove the sensor and inspect the probe electrodes. If they're covered in sludge or bacterial growth (diesel bug), cleaning with electrical contact cleaner and a soft brush may restore function. However, if the sensor has internal corrosion, cracks in the body, or the connector pins are corroded replacement is the only fix. At $19.99, it's usually not worth the gamble. Q: What happens if I ignore the "Water in Fuel" warning? A: Water in diesel fuel causes three problems: (1) Injector tip erosion water droplets hitting the injector nozzle at 26,000+ PSI act like sandblasting, destroying the spray pattern; (2) Fuel system corrosion water promotes rust on ferrous components in the injection pump and fuel lines; (3) Microbial growth bacteria and fungi breed at the water-fuel interface, producing acidic byproducts