Ford F150 Pickup. Instruction - part 1338

2003 ENGINE PERFORMANCE

System & Component Testing - Bi-Fuel - Gasoline/CNG 

INTRODUCTION 

COMPUTERIZED ENGINE CONTROLS 

POWERTRAIN CONTROL MODULE 

Ground Circuits 

Turn ignition off. Disconnect PCM 104-pin connector. PCM is located on right rear of engine compartment. 
Using DVOM, check for continuity between chassis ground and PCM harness connector terminals No. 3, 25, 
51, 76 and 103. See Fig. 1. If continuity exists, see POWER CIRCUITS. If continuity does not exist, repair 
open in affected ground circuit. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS - F150 
article in ELECTRICAL. 

Power Circuits 

WARNING:

Before performing any tests or diagnostics on CNG components or 
systems, read all cautions and warnings in CNG/LPG SAFETY 
PRECAUTIONS article in GENERAL INFORMATION.

NOTE:

System and component testing included in this article is for alternative fuel 
systems only. For gasoline fuel system and component testing, see SYSTEM & 
COMPONENT TESTING - GASOLINE article. Since many computer-controlled 
and monitored components set a Diagnostic Trouble Code (DTC) when a 
malfunction occurs, check for Powertrain Control Module (PCM) DTCs and 
Alternative Fuel Control Module (AFCM) DTCs prior to testing an individual 
system or component. Perform QUICK TEST procedures in SELF-DIAGNOSTICS 
- CNG, FLEX-FUEL & GASOLINE article, or QUICK TEST procedures in SELF-
DIAGNOSTICS - BI-FUEL - GASOLINE/CNG article. If no DTCs are present, 
perform SYMPTOM DIAGNOSIS under SYMPTOMS in TROUBLE SHOOTING - 
NO CODES - BI-FUEL - GASOLINE/CNG article to diagnose driveability 
problems existing when a hard fault code is not present. For specifications, see 
appropriate ON-VEHICLE ADJUSTMENTS - TRUCKS or SERVICE & 
ADJUSTMENT SPECIFICATIONS - EXCURSION & PICKUP article.

NOTE:

Testing individual components does not isolate short or open circuits. Perform 
all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-
megohm input impedance, unless stated otherwise in test procedure. Use 
ohmmeter to isolate shorted or open wiring harness. For identification of 
circuits and terminals referenced in test procedures, see ENGINE 
PERFORMANCE in SYSTEM WIRING DIAGRAMS - F150 article in ELECTRICAL.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - Bi-Fuel - Gasoline/CNG

  

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - Bi-Fuel - Gasoline/CNG

  

1. Ensure ignition is OFF. Using DVOM, check for battery voltage between chassis ground and PCM Keep 

Alive Memory Power (KAPWR) terminal No. 55. See Fig. 1. If battery voltage is present, go to next step. 
If battery voltage is not present, check for open in KAPWR circuit or fuse No. 2 (5-amp), located in 
central junction box. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS - F150 
article in ELECTRICAL.  

2. Turn ignition on. Using DVOM, check for battery voltage between chassis ground and VPWR at PCM 

connector terminals No. 71 and 97. If battery voltage is not present, power is not being supplied from 
PCM power relay. See TEST B: EEC-V POWER RELAY under SYSTEM TESTS in SELF-
DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.  

Fig. 1: Identifying Powertrain Control Module Connector Terminals 
Courtesy of FORD MOTOR CO. 

ALTERNATIVE FUEL CONTROL MODULE 

Ground Circuits 

Turn ignition off. Disconnect AFCM 90-pin connector. AFCM is located in right front of engine compartment. 
Using DVOM, check for continuity between chassis ground and AFCM connector terminals No. 1, 2, 3, 4, 17, 
19, 21, 23, and 75. See Fig. 2. If continuity exists, go to next step. If continuity does not exist, repair open in 
affected ground circuit. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS - F150 article in 
ELECTRICAL. 

NOTE:

Alterative Fuel Control Module (AFCM) is only used on bi-fuel vehicles.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - Bi-Fuel - Gasoline/CNG

  

Fig. 2: Identifying AFCM Connector C1427 Terminals
Courtesy of FORD MOTOR CO. 

Power Circuits 

Turn ignition off. Ensure AFCM 90-pin connector is disconnected. Turn ignition on. Using DVOM, check for 
battery voltage between chassis ground and AFCM VPWR terminals No. 45 and 60. See Fig. 2. If battery 
voltage is not present, power is not being supplied from bi-fuel relay module. Repair open in affected circuit or 
bi-fuel relay module as necessary. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS - 
F150 article in ELECTRICAL. 

ENGINE SENSORS & SWITCHES 

ALT FUEL SWITCH 

For ALT fuel switch or circuit testing, see TEST NB: ALT FUEL INDICATOR under SYSTEM TESTS in 
SELF-DIAGNOSTICS - BI-FUEL - GASOLINE/CNG article. 

FUEL RAIL PRESSURE SENSOR 

Faults in Fuel Rail Pressure (FRP) sensor or circuit should set a Diagnostic Trouble Code (DTC). Perform 
QUICK TEST in SELF-DIAGNOSTICS - BI-FUEL - GASOLINE/CNG article. If no DTC has been set, go to 
TEST DE: FUEL RAIL PRESSURE SENSOR under SYSTEM TESTS in SELF-DIAGNOSTICS - BI-
FUEL - GASOLINE/CNG article for FRP sensor and circuit testing. 

FUEL RAIL TEMPERATURE SENSOR 

Faults in Fuel Rail Temperature (FRT) sensor or circuit should set a Diagnostic Trouble Code (DTC). Perform 
QUICK TEST in SELF-DIAGNOSTICS - BI-FUEL - GASOLINE/CNG article. If no DTC has been set, see 
TEST DA: FUEL RAIL TEMPERATURE under SYSTEM TESTS in SELF-DIAGNOSTICS - BI-FUEL - 
GASOLINE/CNG article for FRT sensor and circuit testing. 

HEATED OXYGEN SENSOR 

Faults in Heated Oxygen Sensor (HO2S) or circuit should set a Diagnostic Trouble Code (DTC). Perform 
QUICK TEST in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article. 

INERTIA FUEL SHUTOFF SWITCH 

Turn ignition off. Locate Inertia Fuel Shutoff (IFS) switch, behind right kick panel. Shake or jar IFS switch to 
cause switch to open. IFS switch reset button should pop up. Fuel pump should not operate and vehicle should 
not start. Push down on reset button. Restart engine. Fuel pump should operate.

NOTE:

For additional gasoline-related sensor and switch testing procedures, see 
SYSTEM & COMPONENT TESTING - GASOLINE article.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - Bi-Fuel - Gasoline/CNG

  

RELAYS & SOLENOIDS 

AUXILIARY RELAY BOX NO. 1 

Perform QUICK TEST in SELF-DIAGNOSTICS - BI-FUEL - GASOLINE/CNG article. If no DTC has been 
set, repair by symptom. See SYMPTOM DIAGNOSIS under SYMPTOMS in TROUBLE SHOOTING - NO 
CODES - BI-FUEL - GASOLINE/CNG article 

FUEL RAIL SOLENOID 

For fuel rail solenoid or circuit testing, see NO START/HARD START IN ALT FUEL - ALT FUEL 
SWITCH INDICATOR IS ON, THEN OFF under SYSTEM TESTS in SELF-DIAGNOSTICS - BI-FUEL - 
GASOLINE/CNG article. 

FUEL TANK VALVE 

For fuel tank solenoid or circuit testing, see NO START/HARD START IN ALT FUEL - ALT FUEL 
SWITCH INDICATOR IS ON, THEN OFF under SYSTEM TESTS in SELF-DIAGNOSTICS - BI-FUEL - 
GASOLINE/CNG article. 

FUEL SYSTEM SAFETY PRECAUTIONS 

BI-FUEL SYSTEM 

NOTE:

If a fault exists in auxiliary relay box No. 1, an AFCM DTC or driveability concern 
should be present.

NOTE:

Auxiliary relay box No. 1 contains bi-fuel power relay and fuel pump cut-off 
relay.

CAUTION: Natural gas in fuel system is at high pressure at all times. To avoid injury 

or fire, release fuel pressure from fuel system before disassembling any 
fuel system component. To release fuel system pressure, follow pressure 
relief procedure. See FUEL SYSTEM PRESSURE RELEASE under FUEL 
SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - F150 PICKUP - BI-
FUEL - GASOLINE/CNG article. After performing fuel system pressure 
relief procedure, a small amount of pressure 3 psi (21 kPa) will remain in 
fuel rail, and high pressure still exists in fuel tanks. Prevent combustion 
from escaping fuel; no smoking, open flames or any kind of arcing.

WARNING:

Use care to prevent combustion from fuel spillage. No smoking, open 
flames or any kind of arcing.

NOTE:

Compressed Natural Gas (CNG) may also be referred to as natural gas. Natural 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - Bi-Fuel - Gasoline/CNG