What causes P1390 on a Ford?

Octane switch left in the wrong position for the test Failed octane adjust switch Open switch circuit Corroded connector PCM input fault

How do I fix P1390 on a Ford?

Set the octane switch per the test procedure and re-run Test switch continuity in both positions Inspect the circuit and connector Verify the PCM sees the switch change Replace the switch if the input never changes

P1390 Octane Adjust Out of Self-Test Range

Q: What does P1390 mean on a Ford?

P1390 — Octane Adjust Out of Self-Test Range. Applies to F-150, Mustang with octane adjust (premium fuel switch).

Category: Powertrain - Computer and Auxiliary Controls
Severity: Check Engine Light
Applies to: F-150, Mustang with octane adjust (premium fuel switch)

What does P1390 mean on a Ford?

P1390 — Octane Adjust Out of Self-Test Range. This Ford-enhanced code applies to F-150, Mustang with octane adjust (premium fuel switch).

Common causes of P1390

Octane switch left in the wrong position for the test
Failed octane adjust switch
Open switch circuit
Corroded connector
PCM input fault

How to fix P1390

Set the octane switch per the test procedure and re-run
Test switch continuity in both positions
Inspect the circuit and connector
Verify the PCM sees the switch change
Replace the switch if the input never changes