Detroit DD15 SPN 97 FMI 3 - Water-in-Fuel Voltage High won't clear

Question

I have a Freightliner Cascadia in the shop with a persistent SPN 97 FMI 3 code. The dash is throwing the water in fuel warning but I have already drained the fuel water separator and the bowl is bone dry. Even with a new filter installed the code stays active and the engine is starting to derate.

Sam Holloway · Accepted Answer

Found the issue was a broken signal wire inside the insulation about 4 inches back from the Davco sensor plug. The wire felt soft when pulled. Replaced the WIF sensor pigtail (Part # A0001534927) and the sensor itself just to be safe. Soldered and heat-shrunk the connections, cleared the codes with DiagnosticLink, and the SPN 97 is finally inactive. Total repair cost was about $85 in parts.

backyard_bart · Answer

FMI 3 usually indicates an open circuit or a short to power. Check the 2-pin connector at the bottom of the Davco housing; those wires often get brittle and snap right at the weather pack seal.

shoptech_carlos · Answer

You need to check the resistance of the sensor itself. If the sensor internal circuit fails, it defaults to the high voltage signal. Also, check pins 51 and 52 at the MCM to ensure you don't have a harness rub-through near the starter.

fleet_chief_42 · Answer

Verify your ground circuit. If the MCM doesn't see the return signal from the WIF sensor, it will trigger FMI 3. Try jumping the pins on the harness side to see if the code changes to FMI 4, which would prove your wiring back to the module is okay.

Detroit DD15 SPN 97 FMI 3 - Water-in-Fuel Voltage High won't clear

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