Case Study: F-150 multiple systems inoperative - one cause

July 19, 2023

The customer had her F-150 towed into the shop because the radio, HVAC controls, and the electric power steering were inoperative.

Richard Diegle

Related To: ALLDATA

Vehicle: 2016 Ford F-150, 4WD, V8-5.0L, Automatic transmission/transaxle

Mileage: 122,872

Problem: The customer had her F-150 towed into the shop because the radio, HVAC controls, and the electric power steering were inoperative.

Case details: The technician connected a scan tool and found the following diagnostic trouble codes (DTCs).

P0563 - System Voltage High
P0625 - Generator Field Terminal Circuit Low
P065B - Generator Control Circuit Range/Performance

There seemed to be no correlation between the customer’s concerns and the DTCs, so the technician called ALLDATA Tech-Assist. The consultant advised that low voltage could negatively impact all the systems on the list. He recommended checking the charging system first, starting by verifying there was battery voltage on the brown/red (BRN/RED) wire at the alternator.

The technician tested the charging system and found it was not working properly. A close inspection of the wiring near the alternator revealed that the BRN/RED wire was corroded about six inches from the alternator.

Confirmed repair: He repaired the wiring, cleared the DTCs, verified the charging system was working correctly and road-tested the vehicle. All systems worked properly. Problems solved!

About the Author

Richard Diegle | Senior Automotive Editor for ALLDATA

Rich Diegle has been in the automotive industry since 1978. After graduating from a local community college, he began working at a Nissan dealership as a used car technician. Since then, he’s worked as a Nissan and ASE master automotive technician, shop owner, marketing copywriter, automotive editor, public relations manager, instructor, ALLDATA Tech-Assist team manager, and a senior automotive editor.