SAE J1939 SPN and FMI fault codes for automatic and manual transmissions. Covers electronic transmission controllers, transmission fluids, gear selection, torque converter, and driveline diagnostic parameters for commercial vehicles and off-highway equipment.
Diagnostic Code SPN 750 FMI 11: Meaning and Fix SPN 750 FMI 11 indicates the transmission turbine speed sensor signal is invalid for an unknown reason. This code often surfaces after a recent ECM swap or transmission overhaul, where residual debris or a slightly misaligned sensor triggers the fault. The ECM cannot determine if the … Read more
Diagnostic Code SPN 6912 FMI 3: Meaning and Fix SPN 6912 FMI 3 indicates the transmission control module (TCM) detects voltage above normal on the rotational speed sensor circuit for internal component #2, commonly a clutch-pack shaft. This fault frequently appears after a transmission rebuild or when a sensor pigtail is pinched during bell housing … Read more
Diagnostic Code SPN 5610 FMI 2: Meaning and Fix The SPN 5610 FMI 2 fault code indicates an erratic, intermittent, or incorrect data reading on the transmission input clutch’s calculated load. This can happen after a transmission repair or when a new ECM is installed, often leading to unexpected clutch behavior. Technicians frequently encounter this … Read more
Diagnostic Code SPN 560 FMI 9: Meaning and Fix SPN 560 FMI 9 indicates the Electronic Transmission Controller 1 is transmitting the driveline engaged status at an abnormal update rate, outside the expected 10-100 ms window. This fault commonly appears after a forced DPF regeneration or ECM flash update, where bus timing is temporarily disrupted. … Read more
Diagnostic Code SPN 4177 FMI 6: Meaning and Fix The SPN 4177 FMI 6 fault code indicates an electrical issue related to the transmission oil life remaining sensor, causing inaccurate readings. This code often arises in vehicles where recent electrical work has been performed, such as after replacing the ECM or wiring harnesses. The issue … Read more
Diagnostic Code SPN 3359 FMI 6: Meaning and Fix The SPN 3359 FMI 6 fault signifies a current issue in the transmission oil filter restriction switch circuit. This fault often appears after transmission maintenance or when replacing the transmission control module (TCM). The code is triggered when the current in the circuit exceeds normal parameters … Read more
Diagnostic Code SPN 3359 FMI 3: Meaning and Fix SPN 3359 FMI 3 indicates the transmission oil filter restriction switch circuit has detected voltage above normal or a short to high source. In practice, this code often appears after a transmission fluid change or filter replacement if the switch connector is accidentally pinched or contaminated … Read more
Diagnostic Code SPN 3359 FMI 14: Meaning and Fix SPN 3359 FMI 14 indicates the transmission oil filter restriction switch has reported a ‘Special instructions’ state, meaning the ECM received a signal pattern not fitting normal restriction/no-restriction or error codes. Technicians frequently encounter this fault after replacing the transmission oil filter without performing the required … Read more
Diagnostic Code SPN 3359 FMI 11: Meaning and Fix SPN 3359 FMI 11 indicates the transmission control module cannot determine the root cause of transmission oil filter restriction switch malfunction. This commonly occurs during fleet maintenance when technicians discover intermittent transmission performance issues after scheduled service intervals. The ECM receives inconsistent or corrupted signals from … Read more
Diagnostic Code SPN 191 FMI 3: Meaning and Fix SPN 191 FMI 3 indicates that the transmission output shaft speed sensor is reading a voltage higher than normal, potentially due to a short circuit. This fault is commonly encountered after a forced DPF regeneration, which can cause voltage fluctuations. Technicians often find this issue in … Read more