Ford F150 Pickup. Instruction - part 1373

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Crank the engine.  

Does the test lamp blink consistently and brightly (one blink per engine revolution)? If yes, go to next 
step. If no, replace PCM. Program new PCM. See PROGRAMMING . 

8) Check The ALT Fuel Injector Driver Circuit 

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Connect a test lamp between the right bank ALT fuel injector VPWR circuit, harness side, and the 
right bank ALT fuel driver circuit, harness; and between the left bank ALT fuel injector VPWR 
circuit, harness side, and the left bank ALT fuel injector driver circuit, harness side.  

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Crank the engine.  

Does the test lamp blink consistently and brightly (one blink per engine revolution) for each bank? If yes, 
go to next step. If no, the injector drivers are operating correctly. See NO-START/NORMAL CRANK 
under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE 
article. 

9) Check For Correct AFCM Operation 
 

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Disconnect the AFCM.  

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Check for corrosion and pushed out pins.  

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Connect the AFCM connector and make sure it is seated correctly.  

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Operate the system and verify the concern is still present.  

Is the concern still present? If yes, replace AFCM. If no, the system is operating correctly at this time. 
Concern may have been caused by a loose or corroded connector. 

TEST AB: NO START - GASOLINE 

Diagnostic Aids 

Enter this test only when all steps under QUICK TEST have been successfully completed and engine still does 
not start or if directed here from another test or chart. This test is only intended to diagnose:  

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AFCM  

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Circuitry  

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Fuel Pump  

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Gasoline Relay  

For circuit wiring, see Fig. 18 . 

Testing 

NOTE:

Check at least one fuel injector on each bank.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - Bi-Fuel - Gasoline/CNG

  

1) Check The PCM For DTCs 
 

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Key off.  

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Connect the scan tool.  

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Key on, engine off.  

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Access the PCM.  

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Carry out the PCM self-test.  

Are any PCM DTCs present? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-
DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article. If no, go to next step. 

2) Check The Gasoline Injectors VPWR Circuit 
 

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Key off. 

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Disconnect two gasoline injectors.  

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Key on, engine off.  

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Measure the voltage between the right bank gasoline injector VPWR circuit, harness side and 
ground; and between the left bank gasoline injector VPWR circuit, harness side and ground.  

Are the voltages greater than 10 volts? If yes, go to next step. If no, repair the circuit in question. 

3) Check The Gasoline Injector Driver Circuit 
 

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Connect a test lamp between the right bank gasoline injector VPWR circuit, harness side and the 
right bank gasoline injector driver circuit, harness side; and between the left bank gasoline injector 
VPWR circuit, harness side and the left bank gasoline injector driver circuit, harness side.  

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Crank the engine.  

Does the test lamp blink consistently and brightly (one blink per engine revolution)? If yes, go to next 
step. If no, go to step 10) . 

4) Check The Fuel Pump PWR Circuit For Voltage 
 

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Key off.  

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Disconnect the fuel pump connector C463.  

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Key on, engine off.  

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Access the PCM.  

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Command the fuel pump on.  

NOTE:

Check at least one fuel injector on each bank.

NOTE:

Check at least one fuel injector on each bank.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - Bi-Fuel - Gasoline/CNG

  

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Measure the voltage between the fuel pump connector C463 PWR circuit, harness side and ground. 
See Fig. 7 .  

Is the voltage greater than 10 volts? If yes, go to next step. If no, go to step 6) . 

5) Check The Fuel Pump Control Circuit 
 

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Command the fuel pump off.  

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Key off.  

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Measure the resistance between the fuel pump connector C463 ground circuit, harness side and 
ground.  

Is the resistance less than 5 ohms? If yes, verify fuel system integrity and pressure. If no, repair the 
circuit. 

6) Check The Gasoline Relay Terminal No. 30 For Voltage 

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Command the fuel pump off.  

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Key off.  

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Disconnect the gasoline relay connector C1218.  

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Key on, engine off.  

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Access the PCM.  

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Command the fuel pump on.  

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Measure the voltage between the gasoline relay connector C1218 terminal No. 30, harness side and 
ground. See Fig. 11 .  

Is the voltage greater than 10 volts? If yes, go to next step. If no, repair the circuit. 

7) Check The Gasoline Relay Control Circuit For A Short To Ground 
 

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Command the fuel pump off.  

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Key on, engine off.  

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Measure the resistance between the gasoline relay connector C1218 terminal No. 86, harness side 
and ground.  

Is the resistance greater than 10,000 ohms? If yes, go to step 9) . If no, go to next step. 

8) Check The AFCM For An Internal Short To Ground 
 

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Key off.  

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Disconnect the AFCM connector C1427.  

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Measure the resistance between the gasoline relay connector C1218 terminal No. 86, harness side 

NOTE:

Gasoline relay may also be referred to as the fuel pump cut-off relay.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - Bi-Fuel - Gasoline/CNG

  

and ground.  

Is the resistance greater than 10,000 ohms? If yes, go to step 10) . If no, repair the circuit. 

9) Check The Fuel Pump PWR Circuit For An Open 
 

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Measure the resistance between the gasoline relay connector C1218 terminal No. 87a, harness side 
and the fuel pump connector C463 PWR circuit harness side. See Fig. 7 .  

Is the resistance less than 5 ohms? If yes, install a new gasoline relay. If no, repair the circuit. 

10) Check For Correct AFCM Operation 
 

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Disconnect the AFCM.  

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Check for corrosion and pushed out pins.  

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Connect the AFCM connector and make sure it is seated correctly.  

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Operate the system and verify the concern is still present.  

Is the concern still present? If yes, install a new AFCM. If no, the system is operating correctly at this 
time. Concern may have been caused by a loose or corroded connector. 

TEST AC: NO START/HARD START IN ALT FUEL - ALT FUEL SWITCH INDICATOR IS ON, 
THEN OFF 

Diagnostic Aids 

Enter this test only when all steps under QUICK TEST have been successfully completed and engine still does 
not start or if directed here from another test or chart. This test is only intended to diagnose:  

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AFCM  

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ALT Fuel Relay  

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Circuitry  

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Fuel Tank Solenoid  

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Fuel Rail Solenoid  

NOTE:

This condition may cause an auto switch to gasoline mode.

NOTE:

During bi-fuel diagnostics, intermittent failures are possible. Perform wiggle 
test and tap lightly on relays during testing. Ensure vehicle has CNG before 
continuing with diagnostics.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - Bi-Fuel - Gasoline/CNG