TSB 21-2176

Some 2020-2021 F-Super Duty vehicles may exhibit a condition where the engine will not turn off and/or have various electrical symptoms including a dead battery, horn stays on and no crank/no start. The vehicle may also have an illuminated anti-lock braking system (ABS) Indicator with DTCs C0020 and U3003 in the ABS module. This may be a result of water/moisture intrusion into the battery junction box (BJB). The BJB is located under the hood of the vehicle. This water/moisture intrusion may be related to the BJB cover not installed completely or broken cover tabs/locking fingers allowing water/moisture into the BJB. To correct the condition, follow the Service Procedure steps to inspect for water/moisture intrusion into the BJB and replace the BJB if water/moisture intrusion is found.