Ford F150 Pickup. Instruction — part 1529

29) Check Voltage Between VREF & SIG RTN Circuits At FTP Sensor

Ensure ignition switch is turned to ON position. Using a DVOM, measure voltage between VREF and
SIG RTN circuits at FTP sensor harness connector. See Fig. 268 or Fig. 269 . If voltage is 4-6 volts, go to
next step. If voltage is not 4-6 volts, VREF voltage is out of range. Go to TEST C, step 1).

30) Check FTP Circuit For Short To SIG RTN Or PWR GND In Harness

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose,
damaged or corroded terminals. Disconnect scan tool from DLC. Using a DVOM, measure resistance
between FTP circuit, and SIG RTN circuit at PCM harness connector, and battery negative cable. If both
resistance measurements are more than 10 k/ohms, replace PCM. If either resistance measurement is 10
k/ohms or less, repair short to SIG RTN or PWR GND circuit in FTP circuit.

33) For KOEO, KOER & Continuous Memory DTC P0453: Check For High FTP Sensor Voltage
DTC P0453 is set when PCM detects Fuel Tank Pressure (FTP) sensor input signal exceeds maximum
allowable parameter of 4.5 volts. Possible causes are:

z

FTP Circuit Open

z

VREF Shorted To VPWR

z

Faulty Powertrain Control Module (PCM)

z

FTP Circuit Shorted To VREF Or VPWR

z

SIG RTN Circuit Open

z

Faulty FTP Sensor

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition
switch to ON position. Using scan tool, access FTP V PID from PID/DATA MONITOR & RECORD
menu. If FTP V PID is not available on scan tool, measure voltage by backprobing between FTP and SIG
RTN circuits at PCM harness connector. See PCM CONNECTOR IDENTIFICATION and Fig. 268 or
Fig. 269 . If voltage measurement on DVOM or PID voltage is more than 4.5 volts, go to next step. If
voltage is 4.5 volts or less, DTC P0453 is intermittent. Check for intermittent faults. Go to TEST Z, step
1).

34) Check FTP Circuit For Short To VPWR

Turn ignition switch to OFF position. Disconnect FTP sensor connector. Turn ignition switch to ON
position. Using a DVOM, measure voltage between negative battery terminal and FTP circuit at FTP

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 30) to step 33). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

FTP sensor input with no pressure or vacuum on fuel tank should be 2.37-
2.97 volts.

2003 Ford Pickup F150

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

sensor harness connector. See Fig. 268 or Fig. 269 . If voltage is 10.5 volts or less, go to step 36). If
voltage is more than 10.5 volts, a short to VPWR exists. Go to next step.

35) Check FTP Circuit For Short To VPWR Circuit In Harness

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose,
damaged or corroded terminals. Turn ignition switch to ON position. Using a DVOM, measure voltage
between negative battery terminal and FTP circuit at PCM harness connector. See PCM CONNECTOR
IDENTIFICATION and Fig. 268 or Fig. 269 . If voltage is more than 10.5 volts, repair short to VPWR
in FTP circuit. If voltage is 10.5 volts or less, replace PCM.

36) Check Opposite Induced Low FTP Signal

Turn ignition switch to OFF position. Connect a jumper wire between SIG RTN and FTP circuits at FTP
sensor harness connector. Turn ignition switch to ON position.

Using scan tool, access FTP V PID from PID/DATA MONITOR & RECORD menu. If FTP V PID is not
available on scan tool, measure voltage by backprobing between FTP and SIG RTN circuits at PCM
harness connector. See PCM CONNECTOR IDENTIFICATION and Fig. 268 or Fig. 269 . If voltage
measurement on DVOM or FTP V PID value is less than 0.1 volt, remove jumper wire and go to next
step. If voltage measurement on DVOM or FTP V PID value is 0.1 volt or more, unable to induce
opposite signal. Go to step 39).

37) Check For In Range Voltage Between VREF & SIG RTN Circuits At FTP Sensor

Ensure ignition switch is in ON position. Using a DVOM, measure voltage between VREF and SIG RTN
circuits at FTP sensor harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts,
VREF voltage is out of range. Go to TEST C, step 1).

38) Check FTP Circuit For Short To VREF In Sensor Or Harness

Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance
between FTP and VREF circuits at PCM harness connector (both VREF terminals on 150-pin PCM). See
PCM PWR GND, SIG RTN & VREF TERMINAL IDENTIFICATION table. If resistance is more
than 10 k/ohms, replace FTP sensor. See FUEL TANK PRESSURE SENSOR under FUEL SYSTEMS in
appropriate REMOVAL & INSTALLATION article. Perform EVAPORATIVE EMISSIONS
SYSTEM LEAK TEST under SYSTEM TESTS (EVAPORATIVE EMISSION) to verify repair. If
resistance is 10 k/ohms or less, repair short to VREF in FTP circuit.

39) Check FTP Circuit For Open In Harness

Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance
of FTP circuit between PCM harness connector and FTP sensor harness connector. See PCM
CONNECTOR IDENTIFICATION and Fig. 268 or Fig. 269 . If resistance is less than 5 ohms, go to

NOTE:

If a scan tool communication concern exists, remove jumper wire and go
to step 41).

2003 Ford Pickup F150

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

next step. If resistance is 5 ohms or more, repair open in FTP circuit.

40) Check For Open SIG RTN Circuit Between PCM & FTP Sensor

Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance of SIG RTN circuit
between PCM harness connector and FTP sensor harness connector. If resistance is less than 5 ohms, go
to next step. If resistance is 5 ohms or more, repair open in SIG RTN circuit.

41) Check FTP Circuit For Short To VREF In PCM

Ensure ignition switch is turned to OFF position and PCM is disconnected. Using a DVOM, measure
resistance between FTP and VREF circuits at PCM harness connector (both VREF terminals on 150-pin
PCM). See PCM PWR GND, SIG RTN & VREF TERMINAL IDENTIFICATION table. If
resistance is more than 10 k/ohms, replace PCM. If resistance is 10 k/ohms or less, repair short to VREF
in FTP circuit.

43) For Continuous Memory Only DTC P0457: Check For Missing Or Leaking Fuel Filler Cap
DTC P0457 is set when PCM detects a fuel tank pressure decreases more than 7 in. H2O within 30
seconds after refueling, or excessive purge (fuel vapor) flow more than .06 lb. per minute. Possible causes
are:

z

Fuel Filler Cap Not Installed After Refueling (CHECK FUEL CAP Indicator May Be Illuminated)

z

Fuel Filler Cap Loose Or Cross-Threaded

Check for missing, loose or cross-threaded fuel filler cap. Repair, reinstall or replace fuel filler cap as
necessary. Perform PCM RESET PROCEDURE under CLEARING CODES under SELF-
DIAGNOSTIC SYSTEM to clear DTCs. Perform EVAPORATIVE EMISSIONS SYSTEM LEAK
TEST under SYSTEM TESTS (EVAPORATIVE EMISSION) to verify repair. After test is complete,
repeat QUICK TEST. If DTC P0455 is present, perform TEST B: DTC P0455: MAJOR LEAK OR
NO FLOW DETECTED IN EVAP SYSTEM under SYSTEM TESTS (EVAPORATIVE EMISSION).
If a concern with fuel filler cap was not found, perform PCM RESET PROCEDURE under
CLEARING CODES under SELF-DIAGNOSTIC SYSTEM to clear DTCs. Perform EVAPORATIVE
EMISSIONS SYSTEM LEAK TEST under SYSTEM TESTS (EVAPORATIVE EMISSION) to verify
repair. After test is complete, repeat QUICK TEST. If DTC P0455 is present, perform TEST B: DTC
P0455: MAJOR LEAK OR NO FLOW DETECTED IN EVAP SYSTEM under SYSTEM TESTS
(EVAPORATIVE EMISSION). Otherwise, inform vehicle operator that it is important to immediately
install fuel filler cap after every refueling.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 41) to step 43). 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 43) to step 65). No test procedures have been omitted.

2003 Ford Pickup F150

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

Fig. 270: Identifying CV Solenoid Circuits & Connector Terminals
Courtesy of FORD MOTOR CO.

65) For KOEO, KOER & Continuous Memory DTC P0446 & P1451: Check VPWR Voltage To CV
Solenoid
DTC P0446 or P1451 is set when PCM detects EVAP Control System Canister Vent (CV) solenoid
circuit signal falls below minimum or exceeds maximum allowable parameters for a specified CV duty
cycle. Possible causes are:

z

VPWR Circuit Open

z

CV Solenoid Circuit Open, Or Shorted To Chassis GND, PWR GND Or VPWR

z

Faulty CV Solenoid

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

2003 Ford Pickup F150

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