Case Study: Ford Fusion’s battery causing intermittent low idle, stalling, and mil

June 7, 2022
The owner brought her vehicle to the shop because the malfunction indicator light (MIL) was on, and the engine would occasionally stall when coming to a stop.

Vehicle: 2015 Ford Fusion, FWD, L4-2.5L, Automatic Transmission/Transaxle

Mileage: 128,674

Problem: The owner brought her vehicle to the shop because the malfunction indicator light (MIL) was on, and the engine would occasionally stall when coming to a stop.

Case Details: The technician connected a scan tool and found the idle speed to be about 500 RPM in gear, and he retrieved the following diagnostic trouble codes (DTCs):

  • P0505 - Idle Control System
  • P0506 - Idle Control System - RPM Lower Than Expected 

No vacuum leaks were present. After a few more basic checks, the technician called ALLDATA Tech-Assist for some diagnostic advice. The consultant recommended testing the battery and the entire charging system. He also advised cleaning the throttle body and resetting the memory. The battery failed a load test, and the battery terminals were corroded.

Confirmed Repair: The technician replaced the battery, cleaned all connections and cleaned the throttle body. He also reset the keep alive memory (KAM). Once the idle was readapted by the computer, the engine began idling at 650 in drive (D). The technician took the vehicle on a test drive to find the stalling problem was gone. Fixed!

Reprinted with permission from ALLDATA.

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