Caterpillar Fault Code
Free · no signupSPN 3547 FMI 3
High Idle / MIL On
System
Aftertreatment
Symptom
High Idle / MIL On
Diagnosis & fix steps
LOGIC: Water-in-Fuel Indicator voltage above normal.
ACTION: Drain the primary fuel filter water bowl and inspect the sensor probe for corrosion.
Red Seal field insights
Specs: Signal > 4.8Vdc.
PRO-TIP: Often triggered by a cracked sensor housing allowing moisture into the plug during pressure washing.
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