Ford F150 Pickup. Instruction - part 1612

procedures may lead to PCM setting a DTC which may help in diagnosis. To reproduce conditions creating an 
intermittent fault, use the following methods:  

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Lightly vibrate component.  

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Heat component.  

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Wiggle or bend wiring harness.  

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Spray component with water.  

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Remove/apply vacuum source.  

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for 
self-diagnostic DTCs. See QUICK TEST in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE 
article. Use test results to identify a faulty component or circuit. 

WIRING DIAGRAMS 

CARS 

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On Crown Victoria, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Focus, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Grand Marquis, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On LS, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Marauder, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Mustang, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Sable, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Taurus, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Thunderbird, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Town Car, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On ZX2, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

TRUCKS 

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On Aviator, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Cab and Chassis F350 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING 
DIAGRAMS article.  

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On Cutaway E350 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS 
article.  

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On Econoline E150, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Econoline E250, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Econoline E350 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS 
article.  

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On Escape, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article. 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Trouble Shooting - No Codes - CNG, Flex-Fuel & Gasoline

  

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On Expedition, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Explorer, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Explorer Sport, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Explorer Sport Trac, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Excursion, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On E450 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On E550 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On F450 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On F550 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Mountaineer, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Navigator, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Pickup F150, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On Pickup F250 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS 
article.  

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On Pickup F350 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS 
article.  

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On Ranger, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article.  

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On RV Cutaway E350 Super Duty, see ENGINE PERFORMANCE in SYSTEM WIRING 
DIAGRAMS article.  

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On Windstar, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article. 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Trouble Shooting - No Codes - CNG, Flex-Fuel & Gasoline

  

2003 ENGINE PERFORMANCE

Theory & Operation - Bi-Fuel - Gasoline/CNG 

INTRODUCTION 

This article covers basic description and operation of bi-fuel engine performance-related systems and 
components. Bi-fuel refers to the F150 Pickup 5.4L that can operate using gasoline or alternative fuel. 
Alternative fuel may be either Compressed Natural Gas (CNG) or Liquefied Petroleum Gas (LPG). Bi-fuel 
vehicles are either gasoline/CNG, or gasoline/LPG. Bi-fuel systems are separate and have unique components. 
Alternative fuels are not compatible and should not be mixed or substituted. This article covers only 
gasoline/CNG bi-fuel vehicles. For gasoline/LPG bi-fuel vehicles, see THEORY & OPERATION - BI-FUEL 
- GASOLINE/LPG . For illustrations of bi-fuel system components, see Fig. 1 . Read entire article before 
diagnosing vehicles or systems with which you are not completely familiar. 

Switching vehicle operation between gasoline and CNG is performed using ALT/GAS fuel switch inside 
vehicle before ignition is turned on. If vehicle runs out of alternative fuel, system will automatically switch to 
gasoline operation. 

Fig. 1: Identifying Bi-Fuel Compressed Natural Gas System Components

NOTE:

Compressed natural gas may also be referred to as natural gas. Natural gas is 
lighter than air.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - Bi-Fuel - Gasoline/CNG

  

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - Bi-Fuel - Gasoline/CNG

  

Courtesy of FORD MOTOR CO. 

COMPUTERIZED ENGINE CONTROLS 

ALTERNATIVE FUEL CONTROL MODULE 

The Alternative Fuel Control Module (AFCM) receives input from sensors and other electronic components 
(switches, relays). Based on the information received and programmed into its memory, the AFCM generates 
output signals to control various relays, solenoids and actuators. The AFCM contains a set of drivers for both 
the gasoline and the alternative fuel injectors. Fuel injector driver signals from the Powertrain Control Module 
(PCM) are used to control both sets of output drivers in the AFCM. Based on fuel selector switch input, the 
AFCM decides which set of injectors is in use, both on key-up and in fuel switchover situations. The bi-fuel 
system will auto-switch to gasoline mode while operating on CNG if the fuel rail pressure is below 75 psi (517 
kPa). 

POWERTRAIN CONTROL MODULE 

Powertrain Control Module (PCM) on bi-fuel models operates just as it would on gasoline models. When 
vehicle is operated in gasoline mode, PCM monitors engine operating conditions by input received from engine 
sensors and AFCM. Control of output actuators determines fuel mixture and idle speed. PCM is located on right 
rear of engine compartment. 

The engine control system consists of PCM, relays, modules, sensors, switches and actuators. PCM sends out 
electrical reference signals to engine sensors and then analyzes input signals. Engine sensors supply PCM with 
specific information, in the form of electrical signals, to determine engine operating conditions. 

PCM uses a memory integrated circuit chip which stores information for Keep Alive Memory (KAM). KAM 
stores memory of vehicle operating conditions and then uses this information for adaptive learning strategy. 
KAM remains powered with ignition off so that input and output information is not lost. 

In the event that one or more input sensors fail, PCM initiates an alternate strategy called Failure Mode Effects 
Management (FMEM) to allow vehicle to maintain driveability. In the event of PCM failure, Hardware Limited 
Operation Strategy (HLOS) will be activated. HLOS is a system of alternate circuitry that provides minimal 
engine operation if PCM fails. During HLOS, all self-test function will stop and system will be controlled by 
electronic hardware. 

Malfunction Indicator Light (MIL) will remain on whenever FMEM or HLOS is in operation. FMEM and 
HLOS substitute a fixed signal and continue to monitor system failure. If signal(s) return to within operating 
limits, PCM will resume normal operation. 

INPUT DEVICES 

NOTE:

Only alternative fuel input devices for CNG bi-fuel vehicles are listed in this 
article. For additional information on gasoline input devices for bi-fuel vehicles, 
see INPUT DEVICES under COMPUTERIZED ENGINE CONTROLS in THEORY & 
OPERATION - CNG, FLEX-FUEL & GASOLINE article.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - Bi-Fuel - Gasoline/CNG