Posted on November 14, 2022 by Jack CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – Troubleshooting and Repair Manual FAULT CODE 16-fc257Fault Code Path Selection Is the engine an ISM? Go to 16-fc257ism Is the engine an ISX? Go to 16-fc257isx Last Modified: 01-Dec-2008 Feedback / Help