P1663 Fuel Demand Command Signal Circuit Malfunction

Category: Powertrain - Fuel/Air Metering
Severity: Check Engine Light
Applies to: Ford diesel models with electronic fuel demand

What does P1663 mean on a Ford?

P1663 — Fuel Demand Command Signal Circuit Malfunction. This Ford-enhanced code applies to Ford diesel models with electronic fuel demand.

Common causes of P1663

Open fuel demand signal wire
Corroded demand connector
Failing demand sensor
Controller input fault
Harness damage

How to fix P1663

Test demand signal through its range
Check circuit continuity
Inspect the connector
Verify controller receives the demand
Repair wiring per tests