SPN 97 FMI 4
Water in Fuel Indicator — Voltage below normal or shorted low.
The sensor circuit voltage is lower than it should ever be, usually near zero.
What the SPN covers: Signals that the fuel/water separator has collected enough water to trip its sensor. More on SPN 97.
What FMI 4 usually points to: Signal wire shorted to ground, a lost 5 V reference, or an open signal wire on a pulled-down circuit. More on FMI 4.
Severity
MEDIUM — fix soon
Drain the separator soon. Water reaching a common-rail system can destroy injectors and pumps.
Likely causes
- Wiring or connector fault in this circuit (most common for electrical FMIs)
- Water collected in the separator bowl
- Contaminated fuel from the supply
- Faulty water-in-fuel sensor or wiring
Checks & fixes (easiest first)
- Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins
- Check the reference voltage, ground and signal at the component per OEM pin-out
- Drain the water separator
- Check fuel from the tank bottom for water
- Inspect the WIF sensor and connector
- Replace the filter element if contaminated
FAQ
What does SPN 97 FMI 4 mean?
Water in Fuel Indicator — voltage below normal or shorted low. The sensor circuit voltage is lower than it should ever be, usually near zero.
Is SPN 97 FMI 4 serious?
Drain the separator soon. Water reaching a common-rail system can destroy injectors and pumps.
What should I check first for SPN 97 FMI 4?
Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins; Check the reference voltage, ground and signal at the component per OEM pin-out; Drain the water separator.