Ford F150 Pickup. Instruction — part 1502

refer to bank No. 1. DTCs P0174 (lean) and P0175 (rich) refer to bank No. 2. Possible causes for these
faults are:

z

Fuel System

Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low
fuel pressure or engine running out of fuel or vapory recovery system fault.

z

Induction System

Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or
improperly seated engine oil dipstick.

z

EGR System

Leaking gasket, stuck EGR valve or leaking diaphragm or EVR.

z

Engine Mechanical

Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.

Inspect engine for obvious defects in specified systems. Repair as necessary. If no faults are found, go to
TEST DC, step 25).

42) Perform KOER Self-Test

Perform KOER ON-DEMAND SELF-TEST. If KOER DTC P1131, P1132, P1151, P1152 P2195,
P2196, P2197 or P2198 is present, go to next step. If none of these DTCs are present, proceed as follows:

z

For Continuous Memory DTCs P0171, P0172, P0174, P0175, P1130 or P1150, go to next step.

z

For any other DTCs, fault may be intermittent. Go to TEST Z, step 1).

43) Check Fuel Pressure
Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Install Natural
Gas Fuel Rail Pressure Gauge Tool Kit (134-00114) to fuel rail Schrader valve. Using scan tool, access
FRP PID (if available) from PID/DATA MONITOR & RECORD menu. With ignition switch turned to
ON position, record FRP sensor PID or fuel pressure gauge reading. Start engine and allow to idle. Again

WARNING:

Fuel system remains under high pressure even when engine is not
running. To avoid injury, release fuel pressure before disconnecting
any fuel system hose or component. See FUEL SYSTEM PRESSURE
RELEASE procedure under FUEL SYSTEM VENTING in appropriate
REMOVAL & INSTALLATION article.

NOTE:

Not all natural gas vehicles are equipped with Fuel Rail Pressure (FRP)
sensor. On vehicles without FRP sensor, use values supplied by fuel rail
pressure gauge.

2003 Ford Pickup F150

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

record FRP sensor PID or fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain
for one minute. Record FRP sensor PID or fuel pressure gauge reading. If fuel pressure readings are 80-
120 psi (552-827 kPa), turn ignition switch to OFF position and go to next step. If fuel pressure readings
are not 80-120 psi (552-827 kPa), turn ignition switch to OFF position and go to TEST HB, step 1).

44) Check Fuel System For Pressure Stability

With fuel pressure gauge installed, cycle ignition switch from OFF to ON position 2 times to pressurize
fuel system (DO NOT start engine). Verify no external leaks are present. If fuel pressure does not remain
within 10 psi (69 kPa) of highest fuel pressure reading after 2 minutes, go to TEST HB, step 1). If fuel
pressure remains within 10 psi (69 kPa) of highest fuel pressure reading after 2 minutes, proceed as
follows:

z

If DTCs P1130, P1150, P0171 P0172, P0174 and P0175 are present or engine is a no-start, go to
next step.

z

If engine does not start, go to next step.

z

If any other DTC is present, go to step 62).

45) Check Fuel System For Pressure Stability With Ignition Switch Turned To ON Position

Using scan tool, access FRP PID (if available) from PID/DATA MONITOR & RECORD menu. If FRP
PID is not available, install Natural Gas Fuel Rail Pressure Gauge Tool Kit (134-00114) to fuel rail
Schrader valve. Cycle ignition switch from OFF to ON (DO NOT start engine). Monitor fuel pressure
reading. If fuel pressure does not remain within 10 psi (69 kPa) of highest fuel pressure reading after 10
seconds, go to step 56). If fuel pressure remains within 10 psi (69 kPa) of highest fuel pressure reading
after 10 seconds, proceed as follows:

z

If engine is a no-start, go to next step.

z

For DTCs P1130, P1150, P0171 and P0174, go to step 55).

46) Check Fuel Injectors Ability To Deliver Fuel

Using scan tool, access FRP PID (if available) from PID/DATA MONITOR & RECORD menu. If FRP
PID is not available, install Natural Gas Fuel Rail Pressure Gauge Tool Kit (134-00114) to fuel rail
Schrader valve. Cycle ignition switch from OFF to ON position 2 times to pressurize fuel system (DO
NOT start engine). Record fuel pressure reading. Locate and disconnect Inertia Fuel Shutoff (IFS) switch.
Crank engine for 10 seconds. If fuel pressure reading remains within 10 psi (34 kPa) of original pressure
reading, go to next step. If fuel pressure drops more than 10 psi (34 kPa) from original pressure reading,
EEC-V system is not the cause of no-start. Diagnose no-start symptom. See NO-START/NORMAL
CRANK under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL &
GASOLINE article.

47) Check VREF Voltage At Natural Gas Module

Turn ignition switch to OFF position. Install NG module breakout box. For NG module location, see
NATURAL GAS MODULE LOCATION table. Connect NG module. Turn ignition switch to ON
position. Using a DVOM, measure voltage between VREF and SIG RTN circuits at NG module breakout
box. See

Fig. 235

. If voltage is 4-6 volts, go to next step (no-starts), or go to step 57) (all others). If

2003 Ford Pickup F150

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

voltage is not 4-6 volts, turn ignition switch to OFF position and go to step 50).

NATURAL GAS MODULE LOCATION

48) Check For Open In PWR GND Circuit

Turn ignition switch to OFF position. Disconnect NG module 60-pin connector. Using a DVOM, measure
resistance of PWR GND circuit between NG module harness connector and negative battery terminal.
See Fig. 235. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open
in PWR GND circuit.

49) Check For Open In PWR GND Circuit In NG Module

Turn ignition switch to OFF position. Disconnect NG module 60-pin connector. Measure resistance
between PWR GND and SIG RTN circuits at NG module. See Fig. 235. If resistance is 5 ohms or more,
replace NG module. If resistance is less than 5 ohms, go to step 57) (no-starts), or reconnect PCM and
NG module and go to TEST A, step 6) (all others).

50) Is VREF More Than 6 Volts

If voltage in step 47) was 6 volts or less, go to next step. If voltage was more than 6 volts, go to step 55).

51) Check Battery Voltage

Using a DVOM, measure voltage across battery terminals. If voltage is more than 10.5 volts, go to next
step. If voltage is 10.5 volts or less, check charging system and battery. See appropriate GENERATORS
& REGULATORS article in STARTING & CHARGING SYSTEMS. Repair as necessary.

52) Check VPWR At NG Module

Turn ignition switch to ON position. Using a DVOM, measure voltage between PWR GND and VPWR
circuits at NG module connector. See Fig. 235. If voltage is 10.5 volts or less, go to next step. If voltage
is more than 10.5 volts, go to step 54).

53) Check Voltage Between VPWR At NG Module & Battery Ground

Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal
and VPWR circuit at NG module connector. See Fig. 235. If voltage is 10.5 volts or less, repair open in
VPWR circuit between NG module and PCM power relay. If voltage is more than 10.5 volts, repair open
in PWR GND circuit.

54) Check VREF Voltage To Fuel Tank Pressure Sensor

Application

Location

Crown Victoria

Front Of Radiator Support

Econoline

On Left Side Of Inner Fender Panel In Engine Compartment

F150 Pickup

On Right Front Side Of Engine Compartment

2003 Ford Pickup F150

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

Turn ignition switch to OFF position. Locate and disconnect Fuel Tank Pressure (FTP) sensor connector.
See FUEL TANK PRESSURE SENSOR LOCATION table. Turn ignition switch to ON position.
Using a DVOM, measure voltage between SIG RTN and VREF circuits at FTP sensor harness connector.
See Fig. 236. If voltage is 4-6 volts, replace FTP sensor. See FUEL TANK PRESSURE SENSOR under
FUEL SYSTEMS in appropriate REMOVAL & INSTALLATION article. If voltage is not 4-6 volts, go
to step 56).

FUEL TANK PRESSURE SENSOR LOCATION

55) Check VREF Circuit For Short To PWR In Harness

Turn ignition switch to OFF position. Disconnect NG module and FTP sensor connectors. Turn ignition
switch to ON position. Using a DVOM, measure voltage between PWR GND and VREF circuits at NG
module harness connector. See Fig. 236. If voltage is less than one volt, replace NG module. If voltage is
one volt or more, repair short to PWR in VREF circuit.

56) Check VREF Circuit For Short To PWR GND

Turn ignition switch to OFF position. Disconnect NG module connector. Using a DVOM, measure
resistance between VREF circuit and the SIG RTN, PWR GND and CASE GND circuits at the NG
module harness connector. See Fig. 235. If all resistance measurements are more than 10 k/ohms, replace
NG module. If any resistance measurement is 10 k/ohms or less, repair short to ground in VREF circuit.

57) Check Fuel Injectors & Harness Resistance From NG Module To Fuel Injectors

Ensure fuel injector harness connectors are connected. Leave ignition switch turned to OFF position and
NG module disconnected. Using a DVOM, measure resistance between VPWR circuit and suspect fuel
injector circuit at NG module harness connector. See NG MODULE FUEL INJECTOR CIRCUIT
TERMINAL IDENTIFICATION table. See Fig. 235. If resistance is 3-6 ohms, go to step 60). If
resistance is not 3-6 ohms, go to next step.

NG MODULE FUEL INJECTOR CIRCUIT TERMINAL IDENTIFICATION

Application

Location

Crown Victoria

Under Vent Box Cover Of Upper Fuel Tank Assembly

Econoline

Under Left Side Center Of Vehicle

F150 Pickup

Part Of Fuel Pump Assembly

Cylinder No.

NG Module Injector Circuit Terminal No.

1

58

2

59

3

39

4

35

5

33

6

42

7

53

2003 Ford Pickup F150

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