P1397 2009 FORD MUSTANG - System Voltage Out Of Self Test Range
Alternator belt loose or missing
Low battery voltage
Faulty Charging System
When is the code detected?
The Engine Control Module (ECM) has detected a voltage range that is higher or lower than expected.
Engine Light ON (or Service Engine Soon Warning Light)
P1397 2009 Ford Mustang Description
The P1397 code indicates that the 12-volt system voltage is too high or too low during the Key On Engine Off (KOEO) or key on engine running (KOER) self-test. It sets if the system voltage falls below or exceeds the calibrated threshold at any time during the KOEO or KOER self-test.