Ford F150 Pickup. Instruction - part 1398

 
Check for loose, leaking, collapsed, kinked, or damaged fuel or vacuum lines. Also check for leaking fuel 
injectors. Ensure driveability symptoms such as, a rough idle, hard-start, miss, surge, hesitate or backfire 
do not exist. Verify sufficient fuel in fuel tank. 

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Electrical Inspection 
 
Check for discharged battery, damaged connectors and wire insulation. Also, check for damaged 
components in fuel system. Ensure there are no blown fuses, and ensure Inertia Fuel Shutoff (IFS) switch 
is not tripped.  

Bend, flex and move wiring and connectors for solenoids and other electrical components for obvious problems 
due to looseness, corrosion, or other damage. If a component is suspected as obvious cause of a fault, correct 
cause before proceeding to TESTING. If all system inspection checks are okay, proceed to TESTING . 

Testing 

1) Check System Integrity 
 
Perform SYSTEM INSPECTION before proceeding. Make any repairs as necessary. If all checks are 
okay, go to next step. 

2) Perform Road Test 
 
Road test vehicle at highway speeds with ALT fuel switch in ALT position. If no surge is present while 
driving, go to next step. If a surge is present while driving, fuel is contaminated. Release fuel pressure. 
See FUEL SYSTEM PRESSURE RELEASE under FUEL SYSTEMS in REMOVAL & 
INSTALLATION - F150 PICKUP - BI-FUEL - GASOLINE/LPG article. Replace fuel system filters. 
Road test vehicle. If surge is no longer present while driving, test is complete. If surge is still present 
while driving, perform COMPUVALVE CHECK under QUICK TEST. If fault still exists, replace 
compuvalve. 

3) Perform Cylinder Power Balance Test With ALT Fuel Switch In GAS Position 
 
Perform cylinder power balance test with ALT fuel switch in GAS position. If there is a noticeable power 
loss in one or more cylinders, go to LACK/LOSS OF POWER under SYMPTOMS in TROUBLE 
SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. If there is no noticeable power 
loss from any one cylinder, go to next step. 

4) Perform Cylinder Power Balance Test With ALT Fuel Switch In ALT Position 
 
Perform cylinder power balance test with ALT fuel switch in ALT position. If there is no noticeable 
power loss from any one cylinder, go to next step. If there is a noticeable power loss in one or more 
cylinders, clear blockage from indicated cylinder's injector sleeve. 

5) Check AFCM MAP PID 
 

 

2003 Ford Pickup F150 

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

  

Ensure MAP sensor damper tube is installed properly and inserted flush against compuvalve body. 
Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, access AFCM and 
select MAP PID from PID/DATA MONITOR & RECORD menu. With KOEO, monitor MAP PID and 
record value. Start engine and warm to normal operating temperature. Allow engine to idle at normal 
operating temperature (hot idle) and record new MAP PID value. MAP PID value should be 13.5-15.0 psi 
with KOEO, and 3-7 psi at hot idle. If MAP PID value is within specification, perform TEST DB: 
MAP/BARO SENSOR . If MAP PID value is not within specification, replace MAP tap assembly with a 
calibrated service part as necessary.  

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. Powertrain Control Module (PCM) and Alternative Fuel 
Control Module (AFCM) transfer data through SCP network. DTCs U1011 (SCP invalid/missing engine air 
intake data), U1071 (SCP invalid/missing engine sensor data) and U1073 (SCP invalid/missing data for engine 
coolant) are set when AFCM does not receive or receives incorrect data from PCM. Possible causes for these 
faults are:  

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Faulty compuvalve.  

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Faulty PCM.  

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SCP communication link.  

Testing 

1) Check Communication With PCM 
Turn ignition off. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, 
access PCM and select an active PID. If communication is possible with PCM, turn ignition off and go to 
next step. If communication is not possible with PCM, go to TEST QA: UNABLE TO ACTIVATE 
SELF-TEST/SCP COMMUNICATION ERROR/DTC NOT LISTED under SYSTEM TESTS in 

NOTE:

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

NOTE:

Always retrieve Powertrain Control Module (PCM) DTCs before Alternate Fuel 
Control Module (AFCM) DTCs. If any network "U" type DTCs are present, repair 
prior to PCM DTCs. If PCM DTCs are retrieved, go to DIAGNOSTIC TROUBLE 
CODE DEFINITIONS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE 
article and service DTCs as necessary.

CAUTION: Always disconnect bi-fuel relay module power supply 3-pin harness 

connector C495 before disconnecting or reconnecting compuvalve 
main harness connector C1294 to avoid damaging compuvalve or 
connectors. See Fig. 6 .

 

2003 Ford Pickup F150 

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

  

SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article. 

2) Check Communication With Compuvalve 
 
Ensure scan tool is connected to DLC. Turn ignition on. Using scan tool, access AFCM and select an 
active PID. If communication is not possible with AFCM, go to next step. If communication is possible 
with AFCM, clear DTCs and retest. If DTC is set again, go to step 5) . 

3) Check Power To Compuvalve 
Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Disconnect 
compuvalve harness connector C1294. Reconnect bi-fuel relay module power supply harness connector 
C495. Turn ignition switch to ON position. Using DVOM, measure voltage between chassis ground and 
compuvalve harness connector C1294 terminals No. 9 and 11 (White wires). See Fig. 7 . If all voltages 
are more than 10 volts, go to next step. If either voltage is 10 volts or less, repair open in affected circuit. 
See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. 

4) Check Ground To Compuvalve 
 
Turn ignition off. Ensure compuvalve harness connector C1294 is disconnected. Using DVOM, measure 
resistance between chassis ground and compuvalve harness connector C1294 terminals No. 57, 59, 61, 
62, 63 and 64 (Black wires). See Fig. 7 . If all resistances are less than 5 ohms, go to next step. If any 
resistance is 5 ohms or more, repair open in affected circuit. See ENGINE PERFORMANCE in 
SYSTEM WIRING DIAGRAMS article in ELECTRICAL. 

5) Check SCP Link To DLC For Open Or Short To Ground 
 
Ensure ignition is off. Ensure compuvalve harness connector C1294 is disconnected. Perform the 
following: 

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Using DVOM, measure resistance between chassis ground and compuvalve harness connector 
C1294 terminals No. 14 and No. 16 (White wires). See Fig. 7 .  

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Using DVOM, measure resistance of SCP (-) circuit between compuvalve harness connector C1294 
terminal No. 16 (White wire) and DLC terminal No. 10 (Pink/Light Blue wire). Fig. 1 and Fig. 7 .  

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Using DVOM, measure resistance of SCP (+) circuit between compuvalve harness connector 
C1294 terminal No. 14 (White wire) and DLC terminal No. 2 (Tan/Orange wire). See Fig. 1 and 
Fig. 7 .  

If all resistances are more than 10 k/ohms between connector C1294 and chassis ground, and less than 5 
ohms between connector C1294 and DLC, perform COMPUVALVE CHECK under QUICK TEST. If 
fault still exists, replace compuvalve. If any resistance measurement is 10 k/ohms or less between 
connector C1294 and chassis ground, or 5 ohms or more between connector C1294 and DLC, repair open 
or short to ground in affected SCP circuit. See ENGINE PERFORMANCE in SYSTEM WIRING 

CAUTION: Always disconnect bi-fuel relay module power supply 3-pin harness 

connector C495 before disconnecting or reconnecting compuvalve 
main harness connector C1294 to avoid damaging compuvalve or 
connectors. See Fig. 6 .

 

2003 Ford Pickup F150 

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

  

DIAGRAMS article in ELECTRICAL.

TEST UA: SCP SINGLE ENDED CIRCUIT FAILURE 

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. Powertrain Control Module (PCM) and Alternative Fuel 
Control Module (AFCM) transfer data through SCP network. DTCs U1260 (SCP (+) single ended circuit 
failure) and U1261 (SCP (-) single ended circuit failure) are set when AFCM does not receive or receives 
incorrect data from PCM. DTC U1262 (SCP communication bus fault) is set when Alternative Fuel Control 
Module (AFCM) has not received messages from Powertrain Control Module (PCM) for longer than 5 seconds. 
Possible causes for these faults are:  

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SCP (+) or SCP (-) communication link for open or short to ground.  

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Faulty compuvalve.  

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Faulty PCM.  

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SCP communication link.  

Testing 

1) Check SCP Link To DLC For Open Or Short To Ground 
Turn ignition off. Disconnect PCM. Disconnect bi-fuel relay module power supply harness connector 
C495. Disconnect compuvalve harness connector C1294. Perform the following: 

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Using DVOM, measure resistance between chassis ground and compuvalve harness connector 
C1294 terminals No. 14 and No. 16 (White wires). See Fig. 7 .  

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Using DVOM, measure resistance of SCP (-) circuit between compuvalve harness connector C1294 
terminal No. 16 (White wire) and DLC terminal No. 10 (Pink/Light Blue wire). Fig. 1 and Fig. 7 .  

z

Using DVOM, measure resistance of SCP (+) circuit between compuvalve harness connector 
C1294 terminal No. 14 (White wire) and DLC terminal No. 2 (Tan/Orange wire). See Fig. 1 and 
Fig. 7 .  

If all resistances are more than 10 k/ohms between connector C1294 and chassis ground, and less than 5 
ohms between connector C1294 and DLC, go to next step. If any resistance measurement is 10 k/ohms or 
less between connector C1294 and chassis ground, or 5 ohms or more between connector C1294 and 
DLC, repair open or short to ground in affected SCP circuit. See ENGINE PERFORMANCE in 

NOTE:

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

CAUTION: Always disconnect bi-fuel relay module power supply 3-pin harness 

connector C495 before disconnecting or reconnecting compuvalve 
main harness connector C1294 to avoid damaging compuvalve or 
connectors. See Fig. 6 .

 

2003 Ford Pickup F150 

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