Damaged, corroded or loose wiring or connectors in the fuel demand signal circuit between the engine control unit and the fuel pump driver module; Faulty fuel pump driver module or its power and earth supplies; Poor battery or charging voltage, or a bad earth, upsetting the module and signal; Failing fuel pump or high pump current draw causing the driver module to fault; Blown fuse or faulty relay in the fuel pump control supply; Fault inside the engine control unit's output driver; Outdated control unit software where the manufacturer has issued an update for this fault.

P1663

Fuel Demand Command Signal Circuit Malfunction.

Other
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
6: AreaComputer and output circuits
63: FaultThe specific fault in that area

What it means

P1663 is a manufacturer-specific code, so its meaning depends on the make. This guide covers the 'Fuel Demand Command Signal Circuit Malfunction' definition used by Ford, Lincoln and Mercury. The engine control unit monitors the signal it sends to request fuel pump output, normally to a fuel pump driver module, and sets the code when the signal circuit is out of range or does not respond as expected. On GM and Saturn it means an oil life lamp circuit fault, and on Lexus an oil control valve bank 2 circuit fault, so confirm the make before following this guide.

Symptoms

Engine management light on
Long cranking or no start
Engine stalling or cutting out, especially under load or when hot
Hesitation, surging or loss of power
Rough running caused by fuel pressure that is too low or erratic
Fuel pump not priming when the ignition is switched on

Possible causes

Damaged, corroded or loose wiring or connectors in the fuel demand signal circuit between the engine control unit and the fuel pump driver modulelikely
Faulty fuel pump driver module or its power and earth supplieslikely
Poor battery or charging voltage, or a bad earth, upsetting the module and signalpossible
Failing fuel pump or high pump current draw causing the driver module to faultpossible
Blown fuse or faulty relay in the fuel pump control supplypossible
Fault inside the engine control unit's output driverrare
Outdated control unit software where the manufacturer has issued an update for this faultrare

How to diagnose

Confirm the vehicle make and model, then read all stored and pending codes and record the freeze frame data (engine temperature, load, battery voltage).
Check battery condition and charging voltage, and clear any related low-voltage or communication codes first.
Inspect the fuel pump driver module, its connectors and the wiring run for water ingress, corrosion, chafing, heat damage or previous repairs. Its location depends on the model.
Check the relevant fuses and relays and the power and earth supplies to the driver module with a multimeter, following the model wiring diagram.
Check the fuel demand signal wire for continuity, short to earth, short to voltage and high resistance between the engine control unit and the driver module.
With a scan tool, watch the commanded fuel pump duty cycle or fuel pressure against actual rail pressure while running or priming, if the vehicle supports it.
Measure fuel pump current draw and fuel pressure against the manufacturer's specification to test the pump itself.
Check for relevant software updates or technical service bulletins for the exact model and engine.

How to fix

Repair or replace damaged wiring, terminals and connectors in the signal circuit, and clean any corrosion.
Replace the fuel pump driver module if its supply and signal circuits test good but it fails to respond correctly.
Replace the fuel pump if it draws excessive current or cannot hold the correct pressure.
Replace faulty fuses or relays after finding out why they failed, and repair poor earth or power supply connections.
Correct battery or charging system faults that cause low voltage.
Update the control unit software only if the manufacturer lists it as a fix for this fault, and replace the control unit only after all else is proven good.

Can I keep driving?

Medium severity

Avoid driving any distance until it is checked. A fault in fuel pump control can cause stalling or a failure to restart, which is unsafe in traffic. If the car drives normally, keep trips short and get it diagnosed soon.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.