SAE J1939 SPN and FMI fault codes for chassis and suspension systems. Covers air suspension controllers, electronic steering, tire pressure monitoring, wheel speed sensors, and vehicle dynamic stability control on heavy-duty commercial vehicles.
Diagnostic Code SPN 906 FMI 9: Meaning and Fix SPN 906 FMI 9 indicates abnormal update rate from the front axle right wheel speed sensor relative to front axle speed reference. This fault commonly appears during ABS system initialization checks or after wheel speed sensor replacement when the ECM detects irregular signal timing. The condition … Read more
Diagnostic Code SPN 906 FMI 31: Meaning and Fix SPN 906 FMI 31 indicates the ECM detects a condition exists on the front axle right wheel relative speed signal, meaning the reported speed deviates abnormally from the vehicle reference speed. This code commonly appears after a forced DPF regeneration when the vehicle is stationary but … Read more
Diagnostic Code SPN 77 FMI 13: Meaning and Fix SPN 77 FMI 13 indicates that the forward rear drive axle temperature sensor is out of calibration. This fault often appears after axle temperature sensor replacements or when vehicles have undergone significant mechanical work, such as axle rebuilds or replacements. Technicians might notice erratic temperature readings … Read more
Diagnostic Code SPN 241 FMI 5: Meaning and Fix SPN 241 FMI 5 indicates tire pressure sensor circuit current below normal or open circuit condition. This fault commonly appears during routine TPMS sensor battery replacement on commercial fleets, when wireless signals fail to reach the ECM receiver module. The tire pressure monitoring system enters failsafe … Read more
Diagnostic Code SPN 1814 FMI 14: Meaning and Fix SPN 1814 FMI 14 indicates that the Vehicle Dynamic Control (VDC) system is not fully operational. This may occur due to a temporary issue like low voltage or due to intentional disabling during diagnostics. In practice, this fault code often appears after electrical system maintenance or … Read more
Diagnostic Code SPN 1814 FMI 1: Meaning and Fix SPN 1814 FMI 1 signals that the Vehicle Dynamic Control (VDC) system reports a status below the normal operational range, meaning it is not fully functional. This often occurs after a low-voltage event during a cold start or following a battery disconnect. Technicians frequently see this … Read more
Diagnostic Code SPN 1592 FMI 5: Meaning and Fix SPN 1592 FMI 5 indicates insufficient current flow or open circuit in the front left wheel speed sensor circuit. This fault commonly appears after equipment operation in muddy conditions where sensor cables experience mechanical stress or after maintenance work involving front axle components. The ECM detects … Read more
Diagnostic Code SPN 7137 FMI 9: Meaning and Fix SPN 7137 FMI 9 indicates the Engine Control Module (ECM) has not received the expected periodic message from the Tire Pressure Monitoring System (TPMS) for tire 25 within the defined time window. This commonly occurs after a wheel position swap or TPMS sensor battery failure, leaving … Read more
Diagnostic Code SPN 7137 FMI 7: Meaning and Fix SPN 7137 FMI 7 indicates tire 25 pressure monitoring system mechanical malfunction where the pressure sensor assembly fails to respond correctly to actual tire pressure changes. This fault commonly appears on commercial vehicles during routine pre-trip inspections when drivers notice tire pressure warning lights remaining illuminated … Read more
Diagnostic Code SPN 7137 FMI 6: Meaning and Fix SPN 7137 FMI 6 indicates a current above normal or grounded circuit in Tire 25 pressure diagnostics. This fault is commonly observed after tire replacements or when the tire pressure monitoring system (TPMS) has been recalibrated incorrectly. Technicians frequently encounter this fault after replacing or servicing … Read more