Diagnostic Overview
Volvo fault code SPN 3064 FMI 11 is an aftertreatment SPN that should be interpreted together with the FMI and vehicle calibration. It is commonly handled as a DEF/SCR system feedback or sensor-rationality concern where the aftertreatment controller is not seeing data that matches expected operation. The truck may continue to operate at first but can enter emissions warning or derate stages if the condition is not corrected.
Likely Causes
Sensor signal rationality issue; NOx or DEF system feedback fault; wiring damage; poor connector contact; DEF dosing problem; contaminated DEF; exhaust leak.
What To Check First
Confirm the exact Tech Tool description, inspect the associated sensor circuit, check DEF quality and dosing data, compare NOx readings, and check exhaust integrity.