Ford F150 Pickup. Instruction - part 1550

present, go to step 48). If FPM PID value is not 75 percent or is not varying between 250-400 percent, 
DTC P1237, P1238 or P1641 is intermittent, go to next step. 

57) Check Fuel Pump Secondary Circuits For Intermittent Open Or Short 
Turn ignition switch to ON position. Using scan tool, access FPM PID from PID/DATA MONITOR & 
RECORD menu. Observe FPM PID value for indication of fault while wiggling and bending FP PWR 
and FP RTN circuits between FPDM and fuel pump. Lightly tap on FPDM to simulate road shock. Fault 
will be indicated by FPM PID value changing from 50 percent, or varying between 85-115 percent. If any 
faults are found, isolate fault and repair as necessary. If no faults are found, go to next step. 

58) Check FP PWR Circuit For Short To Ground 
 
Turn ignition switch to OFF position. Disconnect FPDM. Connect a test light between FP PWR and 
FPDM PWR circuits at FPDM harness connector. Turn ignition switch to ON position. Observe test light 
for indication of fault while wiggling and bending FP PWR circuit between FPDM and fuel pump. If a 
fault is indicated, test light will illuminate (indicating short to ground). If any faults are found, isolate 
fault and repair as necessary. If no faults are found, concern cannot be identified at this time. Turn 
ignition switch to OFF position, reconnect FPDM and go to TEST Z, step 1). 

59) Check FP PWR Circuit For Short To PWR 
 
Turn ignition switch to OFF position. Disconnect FPDM connector. Turn ignition switch to ON position. 
Using a DVOM, measure voltage between chassis ground and FP PWR circuit at FPDM harness 
connector. See Fig. 308-Fig. 311 . If voltage is less than one volt, go to next step. If voltage is one volt or 
more, repair FP PWR circuit for short to PWR. 

60) Check FP RTN Circuit For Short To Ground 
 
Ensure ignition switch is turned to ON position. Using a DVOM, measure voltage between FPDM PWR 
and FP RTN circuits at FPDM harness connector. If voltage is less than one volt, replace FPDM. If 
voltage is one volt or more, repair short to ground in FP RTN circuit. 

61) Check REM/FP PWR & GND Circuit To REM Harness Connector C420d (LS) or C420e 
(Thunderbird) Terminals No. 1 & 2 
 
Ensure Inertia Fuel Shutoff (IFS) switch is not tripped. Disconnect REM connector C420d (LS) or C420e 
(Thunderbird). See Fig. 312. Turn ignition switch to ON position. Using a DVOM, measure voltage 
between REM/FP PWR and GND circuits at REM harness connector C420d (LS) or C420e 
(Thunderbird). If voltage is 10.5 volts or less, go to next step. If voltage is more than 10.5 volts, go to step 
49). 

62) Check REM/FP PWR Circuit Voltage To REM Using Chassis Ground As A Reference 

NOTE:

With no fault detected, FPDM will send a 50 percent duty cycle signal on 
FPM circuit to PCM. FPM PID value should display 50 percent. Depending 
on scan tool being used, some scan tools will display a random value 
between 85-115 percent.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

  

 
Ensure ignition switch is turned to ON position. Using a DVOM, measure voltage between chassis 
ground and REM/FP PWR circuit at REM harness connector C420d (LS) or C420e (Thunderbird). If 
voltage is more than 10.5 volts, repair open GND circuit between REM harness connector C420d (LS) or 
C420e (Thunderbird) and ground point G401 located behind right side rear luggage compartment panel. 
If voltage is 10.5 volts or less, go to next step. 

63) Check For B+ To Fuel Pump Relay Cavity 
Turn ignition switch to OFF position. Remove fuel pump relay from battery junction box in engine 
compartment. Using a DVOM, measure voltage between chassis ground and fuel pump relay cavity No. 
3. See Fig. 307 and Fig. 312 . If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or 
less, check for blown B+ circuit fuse to fuel pump relay, located in battery junction box. If fuse is blown, 
check for short to ground in B+ circuit, or short to power in FP RTN circuit before replacing fuse. If fuse 
is okay, repair open in Red/Blue wire between B+ circuit fuse and fuel pump relay cavity No. 3. 

64) Check For IGN START/RUN Voltage (Through IFS Switch) To Fuel Pump Relay Cavity 
 
Turn ignition switch to OFF position. Disconnect REM 12-pin connector C420a (LS) or C420b 
(Thunderbird). See Fig. 312. Turn ignition switch to ON position. Using a DVOM, measure voltage 
between chassis ground and IGN START/RUN circuit at REM harness connector C420a (LS) or C420b 
(Thunderbird). If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check for 
blown fuse No. 204 (5-amp) in central junction box located behind right kick panel. If fuse is blown, 
check for short to ground in IGN START/RUN circuit before replacing fuse. If fuse is okay, go to step 
69) to isolate open circuit. 

65) Check Ground Circuit To Fuel Pump Relay 
 
Turn ignition switch to OFF position. Using a DVOM, measure resistance of GND circuit between fuel 
pump relay cavity No. 1 and ground point G300 (LS), or G401 (Thunderbird). See Fig. 307 and Fig. 312 . 
See WIRING DIAGRAMS. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or 
more, repair open in GND circuit. 

66) Check REM/FP PWR Circuit Continuity 
 
Using a DVOM, measure resistance of REM/FP PWR circuit between fuel pump relay cavity No. 5 and 
REM harness connector C420d (LS) or C420e (Thunderbird) terminal No. 1. See Fig. 307 and Fig. 312 . 
If resistance is less than 5 ohms, replace fuel pump relay. If resistance is 5 ohms or more, repair open in 
REM/FP PWR circuit. 

67) Check REM/FP PWR, REM GND & Circuits Associated With Fuel Pump Relay For 
Intermittents 
 
Turn ignition switch to OFF position. Disconnect REM 20-pin connector C420d (LS) or C420e 
(Thunderbird), if not previously disconnected. See Fig. 312. Connect test light between REM/FP PWR 

NOTE:

On LS, B+ circuit fuse to fuel pump relay is No. 417 (15-amp). On 
Thunderbird, B+ circuit fuse to fuel pump relay is No. 418 (20-amp).

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

  

and GND circuits at REM harness connector C420d (LS) or C420e (Thunderbird). Turn ignition switch to 
ON position. Observe test light for indication of fault while wiggling and bending REM/FP PWR and 
GND circuits to REM. Shake, wiggle and bend GND, IGN START/RUN and B+ circuits to fuel pump 
relay. Lightly tap on fuel pump relay and IFS switch to simulate road shock. A fault is indicated when test 
light goes off. If any faults are found, isolate fault and repair as necessary. If no faults are found, go to 
next step. 

68) Check FP PWR & FP RTN Circuits For Intermittent Concerns 
 
Turn ignition switch to OFF position. Using a DVOM, measure resistance between FP PWR and FP RTN 
circuits at REM connector C420d (LS) or C420e (Thunderbird). Observe DVOM for indication of fault 
while wiggling and bending FP PWR and FP RTN circuits between REM and fuel pump. Perform same 
procedure with DVOM connected between chassis ground and FP RTN circuit at REM connector C420d 
(LS) or C420e (Thunderbird). A fault is indicated when resistance changes suddenly. If any faults are 
found, isolate fault and repair as necessary. If no faults are found, concern cannot be identified at this 
time. Turn ignition switch to OFF position. Remove DVOM, reconnect REM and go to TEST Z, step 1). 

69) Isolate Open in IGN START/RUN Circuit 
 
Disconnect IFS switch. Using a DVOM, measure resistance between (normally closed) IFS switch 
terminals. Record resistance reading. Also, measure resistance of IGN START/RUN circuit between fuel 
pump relay cavity No. 2 and IFS switch harness connector. See Fig. 312. If both resistance measurements 
are less than 5 ohms, repair open in IGN START/RUN circuit between fuse No. 204 (5-amp) in central 
junction box and IFS switch. If resistance is 5 ohms or more in either measurement, replace IFS switch or 
repair open in IGN START/RUN circuit between fuel pump relay cavity No. 2 and IFS switch. Ensure 
fuel pump motor diode located in battery junction box in luggage compartment is okay. See WIRING 
DIAGRAMS. 

70) Check Battery Voltage With Outputs Commanded On 
Turn ignition switch to OFF position. Connect scan tool to DLC. Disconnect fuel pump connector. Turn 
ignition switch to ON position. Connect a DVOM between battery terminals. Using scan tool, access 
OUTPUT TEST MODE. See OUTPUT TEST MODE under ADDITIONAL SYSTEM FUNCTIONS. 
While monitoring battery voltage, command OUTPUTS ON. Record voltage measurement within 5 
seconds of commanding outputs ON. Command OUTPUTS OFF. If battery voltage is more than 11 volts, 
and go to next step. If battery voltage is 11 volts or less, battery voltage is low. Service battery/charging 
system as necessary. See appropriate GENERATORS & REGULATORS article in STARTING & 
CHARGING SYSTEMS. 

71) Check Ground Circuit To Fuel Pump 
 
Turn ignition switch to OFF position. Connect DVOM between negative battery terminal and FP PWR 
circuit at fuel pump harness connector. See Fig. 308-Fig. 312 . Turn ignition switch to ON position. 
Using scan tool, command OUTPUTS ON. Record voltage measurement within 5 seconds of 

NOTE:

Diagnostic procedures beginning with step 70) are performed when 
directed here from TEST HC, step 2) to diagnose low voltage at fuel pump 
and no DTCs are present.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

  

commanding outputs ON. If voltage is 10.5 volts or less, ground circuit to fuel pump is okay. Go to next 
step. If voltage is more than 10.5 volts, locate and repair high resistance in ground circuit to fuel pump. 
Check all wiring and connectors for fuel pump and FPDM (or REM) for corrosion or damage. Check 
FPDM (or REM) ground connection to chassis ground. Repair as necessary. 

72) Check Voltage To FPDM 
 
Turn ignition switch to OFF position and proceed as follows: 

z

LS & Thunderbird 
 
Disconnect REM connector. Turn ignition switch to ON position. Using a DVOM, measure voltage 
between negative battery terminal and REM/FP PWR circuit at REM harness connector C420d 
(LS) or C420e (Thunderbird). See Fig. 312. If voltage is more than 10.5 volts, go to next step. If 
voltage is 10.5 volts or less, insufficient voltage is being supplied to REM. Go to step 75). 

z

All Others 
 
Disconnect FPDM connector. Turn ignition switch to ON position. Using a DVOM, measure 
voltage between negative battery terminal and FPDM PWR circuit at FPDM harness connector. See 
Fig. 308, Fig. 309, Fig. 310 or Fig. 311 . If voltage is more than 10.5 volts, go to next step. If 
voltage is 10.5 volts or less, insufficient voltage is being supplied to FPDM. Go to step 75).  

73) Check FP PWR Circuit 
 
Turn ignition switch to OFF position and proceed as follows: 

z

Focus, Sable & Taurus 
 
Connect a jumper wire between FPDM PWR and FP PWR circuits at FPDM harness connector. 
Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery 
terminal and FP PWR circuit at fuel pump harness connector. If voltage is more than 10.5 volts and 
is within .5 volt of voltage measured in step 72), turn ignition switch to OFF position and remove 
jumper. Ensure all previous test step results are correct. Check all connectors for corrosion or 
damage. If all previous results are correct and connectors are okay, replace FPDM. If voltage is not 
as specified, isolate high resistance in FP PWR circuit and repair as necessary. 

z

Mustang & ZX2 
 
Connect a jumper wire between FPDM harness connector FPDM PWR circuit and FP PWR circuit 
terminals. Turn ignition switch to ON position. Using a DVOM, measure voltage between negative 
battery terminal and fuel pump harness connector FP PWR terminal. If voltage is more than 10.5 
volts, and is within .5 volt of voltage measured in step 72), turn ignition switch to OFF position and 
remove jumper. Ensure all previous test step results are correct. Check all connectors for corrosion 
or damage. If all previous results are correct and connectors are okay, replace FPDM. If voltage is 
not as specified, isolate high resistance in FP PWR circuit and repair as necessary. 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline