Ford F150 Pickup. Manual — part 1544

z

Open VPWR to LFP relay.

z

Faulty LFP relay.

z

Faulty PCM.

Turn ignition switch to OFF position. Remove low speed fuel pump relay from battery junction relay box
located in engine compartment. Turn ignition switch to ON position. Using a DVOM, measure voltage
between chassis ground and VPWR circuit at low speed fuel pump relay cavity. See Fig. 304. If voltage
is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in VPWR circuit
between PCM power relay and low speed fuel pump relay.

46) Check Low Speed Fuel Pump Relay

Turn ignition switch to OFF position. Using a DVOM, measure resistance between LFP relay terminal
No. 85 and all other LFP relay terminals. See

Fig. 306

. Resistance between LFP relay terminals No. 85

and 86 should be 40-100 ohms. Resistance between LFP relay terminal No. 85 and all other terminals
should be more than 10 k/ohms. If any resistance measurement is not as specified, replace LFP relay. If
all resistance measurements are as specified, go to next step.

47) Check Low Fuel Pump Circuit For Short To PWR In Harness

Ensure ignition switch is turned to OFF position. Disconnect PCM connector. Inspect connector for loose,
damaged or corroded terminals. Repair as necessary. Turn ignition switch to ON position. Using a
DVOM, measure voltage of LFP circuit between chassis ground and LFP relay cavity. If voltage is less
than one volt, go to next step. If voltage is one volt or more, repair short to PWR in LFP circuit.

48) Check LFP Circuit For Short To Ground In Harness

Turn ignition switch to OFF position. Disconnect scan tool from Data Link Connector (DLC). Using a
DVOM, measure resistance between chassis ground and LFP circuit cavity at LFP relay. If resistance is
more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to ground in LFP
circuit.

49) Check For Open LFP Circuit

Using a DVOM, measure resistance of LFP circuit between PCM harness connector and LFP relay
cavity. See PCM CONNECTOR IDENTIFICATION and Fig. 304. If resistance is less than 5 ohms,
replace PCM. If resistance is 5 ohms or more, repair open in LFP circuit.

55) Check For Open Fuel Pump Ground Circuit Through Resistor (F150 Lightning 5.4L SC)

Turn ignition switch to OFF position. Remove low speed fuel pump relay from battery junction relay box
located in engine compartment. Turn ignition switch to ON position. Using scan tool, access FPM PID
from PID/DATA MONITOR & RECORD menu. If FPM PID indicates OFF, no fault is indicated at this

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 49) to step 55). No test procedures have been omitted.

2003 Ford Pickup F150

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

time. Disregard DTC P0232 at this time. Repeat QUICK TEST and continue diagnostics as directed. If
FPM PID indicates ON, check fuel pump relay ground circuit resistor. See Fig. 304. Replace resistor as
necessary. If resistor is okay, repair open circuit between LFP relay, through resistor, to splice. See
WIRING DIAGRAMS.

60) For Continuous Memory Only DTC P1232: Check Low Speed Fuel Pump Primary Circuits
DTC P1232 is set when LFP circuit is commanded ON (grounded), excessive current draw is detected on
LFP circuit; or when LFP circuit is commanded OFF, voltage is not detected on LFP circuit. PCM
expects to detect VPWR voltage through low speed fuel pump relay coil to LFP circuit. Possible causes
are:

z

Open or shorted Low Speed Fuel Pump (LFP) circuit.

z

Open VPWR to LFP relay.

z

Faulty LFP relay.

z

Faulty PCM.

Turn ignition switch to ON position and wait 5 seconds. Using scan tool, access LFPF PID from
PID/DATA MONITOR & RECORD menu. LFPF PID value should indicate NO (indicating PCM detects
VPWR voltage through LFP relay coil and LFP circuit). Observe LFPF PID value for indication of fault
while performing the following:

z

Wiggle and bend LFP circuit between LFP relay and PCM harness connector.

z

Wiggle and bend VPWR circuit between LFP relay and PCM power relay.

z

Lightly tap on LFP relay to simulate road shock.

z

Check connectors for clean, tight connection.

Fault will be indicated by LFPF PID indicating YES. If any faults are found, isolate fault and repair as
necessary. If no faults are found, check for intermittent faults. Go to TEST Z, step 1).

65) Check Resistance Of Fuel Pump Ground Circuit Through Resistor (F150 Lightning 5.4L SC)

Turn ignition switch to OFF position. Remove low speed fuel pump relay from battery junction relay box
located in engine compartment. Using a DVOM, measure resistance of ground circuit through resistor
between LFP relay cavity No. 30 and ground. See Fig. 304 and Fig. 306 . If resistance is less than 7
ohms, go to next step. If resistance is 7 ohms or more, check LFP relay ground circuit resistor. Replace
resistor as necessary. If resistor is okay, repair open in ground circuit.

66) Check For Open Ground Circuit Between LFP Relay & Fuel Pumps

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 55) to step 60). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 60) to step 65). No test procedures have been omitted.

2003 Ford Pickup F150

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

Ensure ignition switch is turned to OFF position. Disconnect fuel pump connectors. Using a DVOM,
measure resistance of ground circuit between LFP relay cavity No. 30 and one of the fuel pump harness
connectors. Repeat resistance measurement for ground circuit in other fuel pump wiring harness. If both
resistance measurements are less than 5 ohms, go to next step. If either resistance measurement is 5 ohms
or more, repair open in appropriate ground circuit.

67) Check Internal Resistances Of Each Fuel Pump

Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance between FP PWR
circuit and ground circuit of one fuel pump. Resistance should be less than 10 ohms. Repeat resistance
check for other fuel pump. If either fuel pump resistance measurement is not within specification, replace
faulty fuel pump(s) as necessary. If both fuel pump resistance measurements are within specification, go
to next step.

68) Check For Open FP PWR Circuit Between FPM Splice & Fuel Pumps

Ensure ignition switch is turned to OFF position. Remove Inertia Fuel Shutoff (IFS) switch relay from
battery junction relay box located in engine compartment. Using a DVOM, measure resistance of FP
PWR circuit between IFS switch relay cavity No. 87 and one of the fuel pumps harness connector. See
Fig. 304. Repeat resistance check for other fuel pump. If both resistance measurements are less than 5
ohms, no fault is indicated. Disregard DTC P0232 at this time. Repeat QUICK TEST. If either resistance
measurement is 5 ohms or more, repair open in FP PWR circuit between fuel pump and FPM circuit
splice to PCM.

70) Hard Start/Lacks Power: Check Ground Circuit Used For High Speed Fuel Pump Operation
Between LFP Relay & Chassis Ground

Turn ignition switch to OFF position. Remove Low Speed Fuel Pump (LFP) relay from battery junction
relay box located in engine compartment. Using a DVOM, measure resistance of ground circuit between
LFP relay cavity No. 87A and chassis ground. See Fig. 304 and Fig. 306 . If resistance is less than 5
ohms, go to next step. If resistance is 5 ohms or more, repair open in ground circuit.

71) Measure Resistance Of Fuel Pump Ground Circuit Through Resistor To Chassis Ground

Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance of ground circuit
through resistor between LFP relay cavity No. 30 and chassis ground. See Fig. 304 and Fig. 306 . If
resistance is less than 7 ohms, go to next step. If resistance is 7 ohms or more, check LFP relay ground
circuit resistor. Replace resistor as necessary. If resistor is okay, repair open in ground circuit.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 68) to step 70). No test procedures have been omitted.

NOTE:

Diagnostic procedures beginning with step 70) are performed when
directed here from SYMPTOMS in TROUBLE SHOOTING - NO CODES -
CNG, FLEX-FUEL & GASOLINE article.

2003 Ford Pickup F150

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

72) Check Normally Closed Contacts Of LFP Relay

Using a DVOM, measure resistance between LFP relay terminals No. 30 and 87A. See Fig. 306. If
resistance is less than 5 ohms, high speed fuel pump circuits are okay. Return to symptom diagnosis that
directed you here under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL &
GASOLINE article. If resistance is 5 ohms or more, replace LFP relay.

75) For KOEO & KOER Only DTC P0230 (Applications With FP Relay Soldered On PDJB Circuit
Board): Check For FP Circuit Cycling At PDJB

DTC P0230 is set when FP output is commanded ON (grounded) and excessive current draw is detected
on FP circuit; or when FP output is commanded OFF, voltage is not detected on FP circuit (PCM expects
VPWR voltage on FP circuit to fuel pump relay coil). Possible causes are:

z

Open or shorted Fuel Pump (FP) circuit.

z

Open VPWR circuit to fuel pump relay.

z

Faulty fuel pump relay.

z

Faulty PCM.

Disconnect Power Distribution Junction Box (PDJB) connector that contains the FP circuit (connector L5
for Expedition and Navigator, or connector "F" for F-Series and Excursion). Connect non-powered test
light between the FP circuit at the applicable PDJB harness connector and the battery positive post. For F-
Series and Excursion, connect a jumper wire between pin F5 of the PDJB and ground (this completes the
ground circuit for the PCM relay). On all models, connect scan tool to DLC. Turn ignition switch to ON
position. Using scan tool, access Output Test Mode. While observing test light, command outputs on and
off. If the test light turns on and off when the outputs are commanded on and off, PCM and FP harness
circuit okay, go to next step. If the test light does not turn on and off when the outputs are commanded on
and off, turn ignition switch to OFF position. Go to step 78).

76) Check VPWR Through FP Relay At PDJB

Turn ignition switch to ON position. Using a DVOM, measure voltage at the FP circuit pin of the PDJB.
If voltage is greater than 10 volts, unable to identify fault. Verify previous test results, see SYMPTOMS
in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. If voltage is 10
volts or less, verify integrity of related fuse(s). If fuses are okay, replace FP relay/PDJB.

78) Check Fuel Pump (FP) Circuit For Short To Power In Harness

Disconnect PCM. Turn ignition switch to ON position. Measure voltage between FP circuit at the
applicable PDJB harness connector and ground. If voltage is less than 1.0 volt, turn ignition switch to

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 72) to step 75). No test procedures have been omitted.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 76) to step 78). No test procedures have been omitted.

2003 Ford Pickup F150

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