05 April, 2025CAT 3406E (Prefix 1MM or 2WS) Fault Code: 68 PID: SPN: 191 FMI: 7 Transmission Not Responding The Engine Control Module (ECM) detects the following conditions: •Three attempts to complete an Eaton Top 2 shift were unsuccessful.•The “Transmission Style” is programmed to “Eaton Top 2”. Probable Causes: 1) ECM Connector/harness2) Shift solenoid failure3) Shift solenoid relay4) Wiring between shift solenoid and ECM5) Gear ratios are programmed incorrectly in the ECM Share on Facebook Opens in a new window. Tweet on Twitter Opens in a new window. Pin on Pinterest Opens in a new window. Back to blog Leave a comment Name * Email * Comment * Please note, comments need to be approved before they are published.