Case Study: Ford F-250 battery goes dead overnight

Feb. 8, 2023
The customer says the battery goes dead overnight. The battery and charging system had been tested and checked out good.

Vehicle: 2009 Ford F-250 Super Duty, 4WD, V8-6.4L Turbo DSL, automatic transmission/transaxle

Mileage: 168,959

Problem: The customer says the battery goes dead overnight. The battery and charging system had been tested and checked out good.

Case details: The technician found a voltage drain at fuse 5 in the smart junction box (SJB). That fuse supplies voltage to multiple internal components of the SJB. He swapped out the SJB, but the battery voltage still dropped overnight.

An ALLDATA Tech-Assist consultant advised that fuse #5 supplies voltage to the brake shift interlock solenoid, which commonly fails in these vehicles. He recommended unplugging the brake shift solenoid to see if the voltage draw went away.

The technician unplugged the brake shift interlock solenoid and the voltage drain at fuse #5 stopped.

Confirmed repair: He replaced the brake shift Interlock solenoid and let the truck sit overnight. The battery held a full charge in the morning, and the engine started numerous times without fail. Fixed!

Reprinted with permission from ALLDATA.

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