Ford F150 Pickup. Manual — part 1629

is wired into fuel pump ground circuit. With low speed fuel pump relay contacts in normally closed position,
there is no extra resistance in ground circuit, allowing high speed operation. For low speed fuel pump operation,
PCM will ground Low Fuel Pump (LFP) circuit, which opens relay contacts, causing fuel pump ground circuit
to pass through a resistor. See Fig. 29 . For additional fuel pump information, see FUEL DELIVERY under
FUEL SYSTEMS (GASOLINE).

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

Fig. 29: Identifying 2-Speed Fuel Pump Circuits
Courtesy of FORD MOTOR CO.

Fuel Pump Driver Module Applications & Applications With Fuel Pump Functions Incorporated In Rear Electronic
Module)

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

Fuel Pump (FP) signal is a duty cycle command sent from PCM to Fuel Pump Driver Module (FPDM). See Fig.
30 . FPDM uses FP command to operate fuel pump at speed requested by PCM or to turn pump off.

Fig. 30: Fuel Pump Duty Cycle Output Definitions
Courtesy of FORD MOTOR CO.

Generator Communication

See GENERATOR COMMUNICATION under PCM CONTROLLED CHARGING SYSTEM under
MISCELLANEOUS CONTROLS.

Idle Air Control Valve

See IDLE AIR CONTROL VALVE ASSEMBLY under IDLE CONTROL SYSTEM under AIR
INDUCTION SYSTEMS.

Intake Manifold Runner Control

See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.

Intake Manifold Swirl Control

See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.

Intake Manifold Tuning Valve

NOTE:

On LS and Thunderbird, FPDM functions are incorporated in Rear Electronic
Module (REM). Fuel pump operation is same as applications using stand-alone
FPDM. REM will communicate diagnostic information through Standard
Corporate Protocol (SCP) BUS (+) and BUS (-) circuits, instead of using a Fuel
Pump Monitor (FPM) circuit.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.

Malfunction Indicator Light

See MALFUNCTION INDICATOR LIGHT under SELF-DIAGNOSTIC SYSTEM.

Secondary Air Injection By-Pass Solenoid

See ELECTRIC SECONDARY AIR INJECTION SYSTEM under SECONDARY AIR INJECTION
SYSTEM.

Solid State Relay

See ELECTRIC SECONDARY AIR INJECTION SYSTEM under SECONDARY AIR INJECTION
SYSTEM.

Thermostat Heater Control

The primary objective for the thermostat heater control is for improvement in fuel economy and thermal
efficiency. The system consists of a high temperature 208°F (98°C) instead of a 194°F (90°C) thermostat that
has a resistive heater within a wax element. See Fig. 31 . The heater is controlled by PCM dependent on engine
speed, throttle position, engine load, vehicle speed, air charge temperature, transmission oil temperature and
engine coolant temperature. During low speed, low load and low air charge temperature conditions, the
thermostat heater is OFF and engine is allowed to operate at an elevated coolant temperature. This should result
in lower internal friction and higher thermal efficiency, both leading to improved fuel economy.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline