Ford F150 Pickup. Instruction - part 1380

Does the SEL_SW PID indicate GAS? If yes, go to next step. If no, go to step 5) . 

3) Check The ALT Fuel Switch For An Internal Short To Voltage 
 

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Key off.  

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Disconnect the ALT fuel switch connector.  

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Key on, engine off.  

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Access the AFCM.  

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Select the SEL_SW PID.  

Does the SEL_SW PID indicate GAS? If yes, go to next step. If no, install a new ALT fuel switch. 

4) Check The ALT Fuel Input Circuit For A Short To Voltage 
 

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Key off.  

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Disconnect the AFCM connector C1427.  

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Key on, engine off.  

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Measure the voltage between the ALT fuel switch connector input circuit, harness side and ground. 
See Fig. 21 .  

Is any voltage indicated? If yes, repair the circuit. If no, go to step 8) . 

5) Check The AFCM For An Internal Short To Ground 
 

z

Key off.  

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Disconnect the AFCM connector C1427.  

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Key on, engine off.  

Is the ALT fuel indicator illuminated? If yes, go to next step. If no, go to step 8) . 

6) Check The ALT Fuel Indicator Control Circuit For A Short To Ground 
 

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Key off.  

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Disconnect the ALT fuel switch connector.  

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Measure the resistance between the ALT fuel switch connector indicator control circuit, harness 
side and ground. See Fig. 21 .  

Is the resistance greater than 10,000 ohms? If yes, install a new ALT fuel switch. If no, repair the circuit. 

7) Check The ALT Fuel Switch Operation 
 

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Key off.  

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Place the ALT fuel switch in the ALT position. 

 

2003 Ford Pickup F150 

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

  

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Key on, engine off.  

Is the ALT fuel indicator illuminated? If yes, the ALT fuel indicator is operating correctly at this time. If 
the concern is intermittent, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - BI-
FUEL - GASOLINE/CNG article. If no, see TEST AE . 

8) 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 U: SCP INVALID OR MISSING DATA 

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  

AFCM GROUND CIRCUITS 

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.

Pin No.

Wire Color

1

Black

2

Black

3

Black

4

Black

17

Black

19

Black

21

Black

23

Black

75

Black

 

2003 Ford Pickup F150 

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

  

Fig. 27: Identifying AFCM Communication, Ground & Power Circuits 
Courtesy of FORD MOTOR CO. 

Testing 

1) Check Communication To The PCM 
 

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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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Access an active PID.  

Is communication possible? If yes, go to next step. If no, see TEST QA: UNABLE TO ACTIVATE 
SELF-TEST/SCP COM under SYSTEM TESTS in SELF-DIAGNOSIS CNG, FLEX-FUEL & 
GASOLINE. 

2) Check Communication To The AFCM 
 

z

Access the AFCM.  

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Access an active PID.  

Is communication possible? If yes, clear the DTCs. Road test the vehicle. Repeat the self-test. If DTC is 

NOTE:

Always retrieve PCM DTCs before AFCM DTCs. See SELF-DIAGNOSTICS - CNG, 
FLEX-FUEL & GASOLINE . Repair any network (Uxxx) DTCs before diagnosing 
powertrain (Pxxx) DTCs.

 

2003 Ford Pickup F150 

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

  

stored again, go to step 6) . If no, go to next step.

3) Check Power To The AFCM 
 

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Key off.  

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Disconnect the AFCM connector C1427.  

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Key on, engine off.  

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Measure the voltage between the AFCM connector C1427 terminal No. 45, harness side and 
ground. See CONNECTOR IDENTIFICATION .  

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Measure the voltage between the AFCM connector C1427 terminal No. 60, harness side and 
ground.  

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

4) Check The AFCM Ground Circuits 
 

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Key off.  

z

Measure the resistance between the AFCM connector C1427 ground circuit terminals, harness side 
and ground. See AFCM GROUND CIRCUITS table.  

Are the resistances less than 5 ohms? If yes, go to next step. If no, repair the circuit in question. 

5) Check The AFCM SCP Circuits 
 

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Measure the resistance between the AFCM connector C1427 terminal No. 87, harness side and the 
DLC connector C251 terminal No. 2, harness side. See CONNECTOR IDENTIFICATION .  

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Measure the resistance between the AFCM connector C1427 terminal No. 88, harness side and the 
DLC connector C251 terminal No. 10, harness side.  

Are the resistances less than 5 ohms? If yes, go to next step. If no, repair the circuit in question. 

6) 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 UA: SCP SINGLE ENDED CIRCUIT FAILURE 

Diagnostic Aids 

 

2003 Ford Pickup F150 

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