Cummins ISB CM550 (1990-94) Fault Code: 111 PID: SID 254 SPN: 629 FMI: 12 Engine Control Module – critical internal failure. Error internal to the ECM related to memory hardware failures or internal ECM voltage supply circuits.

Posted by PerDiezel Solutions on January 16, 2026

This fault code can only be caused by an internal ECM problem. Repairs are not possible for the ECM.

Possible repairs:

1)Replace the ECM.

Cummins ISB CM550 (1990-94) Fault Code: 2559 PID: SPN: 1845 FMI: 4 Transmission ECU to ECM Communication – Abnormal Update Rate

Cummins ISB CM550 (1990-94) Fault Code: 779 PID: SID 051 SPN: 703 FMI: 11 OEM Input – Engine Protection

Cummins ISB CM550 (1990-94) Fault Code: 768 PID: SID 009 SPN: 923 FMI: 11 Output Device Driver (Trransmission Shift Modulation)

Cummins ISB CM550 (1990-94) Fault Code: 599 PID: SID 025 SPN: 640 FMI: 14 Auxiliary Commanded Dual Output Shutdown – Special Instructions

Cummins ISB CM550 (1990-94) Fault Code: 529 PID: SID 051 SPN: 703 FMI: 3 Dual-Output Driver B

Cummins ISB CM550 (1990-94) Fault Code: 528 PID: 93 SPN: 93 FMI: 2 Alternate (Switched) Torque Curve Switch Circuit

WARNING!