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Ford F150 Pickup. Instruction - part 1500

Turn ignition switch to OFF position. Ensure suspect HO2S is disconnected. Disconnect PCM connector
(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM,
measure resistance between suspect HO2S SIG circuit, and PWR GND, SIG RTN, VPWR and VREF
circuits at PCM harness connector (both VREF circuits on 150-pin PCM). See PCM HO2S, PWR GND
& VPWR CIRCUIT TERMINAL IDENTIFICATION table. See PCM CONNECTOR
IDENTIFICATION. If all resistance measurements are more than 10 k/ohms, go to next step. If any
resistance measurement is 10 k/ohms or less, repair short between HO2S SIG and PWR GND, SIG RTN,
VPWR or VREF circuit.

84) Check HO2S SIG & SIG RTN Circuits For Open In Harness

Using a DVOM, measure resistance of HO2S SIG, SIG RTN and VPWR circuits between suspect HO2S
harness connector and PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT
TERMINAL IDENTIFICATION table. See PCM CONNECTOR IDENTIFICATION and Fig. 233.
If all resistance measurements are less than 5 ohms, go to next step. If any resistance measurement is 5
ohms or more, repair open in affected circuit.

85) Check HO2S Circuit Voltage
Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Reconnect
suspect HO2S and PCM harness connectors. Turn ignition switch to ON position. Using scan tool, access
suspect HO2S PID (12 or 22) from PID/DATA MONITOR & RECORD menu. HO2S DTC identification
is as follows:

DTCs P0136, P1137 and P1138 are for HO2S-12.

DTCs P0156, P1157 and P1158 are for HO2S-22.

Refer to illustrations for HO2S identification. See Fig. 230-Fig. 232 . If HO2S PID voltage is more than
1.5 volts, go to step 88). If HO2S PID voltage is 1.5 volts or less, go to next step.

86) Check HO2S Ground Circuit In PCM

Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance
between PWR GND and SIG RTN circuits at PCM connector. See PCM HO2S, PWR GND & VPWR
CIRCUIT TERMINAL IDENTIFICATION table. See PCM CONNECTOR IDENTIFICATION. If
resistance measurement is less than 5 ohms, go to next step. If resistance measurement is 5 ohms or more,
replace PCM.

87) HO2S Circuit Check

Ensure ignition switch is turned to OFF position. Reconnect PCM harness connector(s). Disconnect
suspect HO2S connector. Connect a jumper wire between VPWR and HO2S SIG circuits at suspect
HO2S harness connector. See Fig. 233. Turn ignition switch to ON position. Using scan tool, access
suspect HO2S PID (12 or 22) from PID/DATA MONITOR & RECORD menu. If suspect HO2S PID
voltage is more than 1.5 volts, replace faulty HO2S. If suspect HO2S PID voltage is 1.5 volts or less,

NOTE:

HO2S may be displayed as O2S on scan tool.

2003 Ford Pickup F150

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

replace PCM.

88) Check For Over Voltage On HO2S Circuit In PCM

Turn ignition switch to OFF position. Disconnect suspect HO2S connector. Turn ignition switch to ON
position. Using a DVOM, measure voltage between negative battery terminal and HO2S SIG and SIG
RTN circuits at suspect HO2S harness connector. See Fig. 233. If either voltage measurement is more
than 1.5 volts, replace PCM. If both voltage measurements are 1.5 volts or less, replace HO2S.

100) For KOER Only DTC P1127
Service all other DTCs before proceeding with this test. DTC P1127 indicates that downstream HO2S
heaters were cycled ON during KOER self-test and exhaust temperatures were below a minimum
calibrated value. Possible causes are:

Engine Not At Operating Temperature

Exhaust System Too Cool

Connect scan tool to Data Link Connector (DLC). Using scan tool, access all HO2S HTR PIDs and
HO2S monitor PIDs from PID/DATA MONITOR & RECORD menu. If all HO2S PIDs switch or
indicate ON, perform KOER ON-DEMAND SELF-TEST. If any HO2S PIDs indicate OFF or do not
switch, operate engine until all HO2S PIDs indicate ON. Perform KOER ON-DEMAND SELF-TEST.

110) For KOER Only DTCs P0040, P0041, P1128 & P1129
These DTCs indicate that during KOER self-test, HO2S signal response for a fuel shift corresponds to
incorrect bank (cross between banks). DTC P0040 and P1128 refers to upstream (fuel control) HO2S-11
or HO2S-21. DTC P0041 and P1129 refers to downstream (catalyst monitor) HO2S-12 or HO2S-22.
Possible causes for these faults are:

Crossed HO2S Connectors

Crossed HO2S Wiring At HO2S Connector

Crossed HO2S Wiring At PCM Connector

Turn ignition switch to OFF position. Inspect HO2S wiring harness and connector for indication of being
crossed (stretched wires or wire harnesses incorrectly installed). Repair as necessary. If no faults are
found, go to next step.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 88) to step 100). 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 100) to step 110). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

2003 Ford Pickup F150

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

111) Verify Proper HO2S SIG Terminal Location

Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as
necessary. Disconnect both suspect HO2S harness connectors. HO2S DTC identification is as follows:

DTC P0040 and P1128 is for upstream HO2S-11 and HO2S-21.

DTC P0041 and P1129 is for downstream HO2S-12 and HO2S-22.

Refer to illustrations for HO2S identification. See Fig. 230-Fig. 232 . Using a DVOM, measure resistance
of HO2S SIG circuit between suspect HO2S harness connector and PCM harness connector. See PCM
HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION table. See PCM
CONNECTOR IDENTIFICATION and Fig. 233. If resistance is less than 5 ohms, fault is intermittent
and cannot be duplicated at this time. Go to TEST Z, step 1). If resistance is 5 ohms or more, HO2S
wiring is crossed. Recheck all HO2S wiring terminal locations at PCM and HO2S connectors. Repair as
necessary.

115) For KOEO, KOER & Continuous Memory DTC P0132, P0138, P0152 Or P0158: Check HO2S
Circuit Voltage
The HO2S Sensor Signals are monitored for an over voltage fault. The code is set when HO2S signal
voltage is 1.5 volts or greater. Possible causes are:

HO2S signal circuit shorted to heater power inside of HO2S sensor.

HO2S signal circuit shorted to VPWR or VREF in harness.

PCM failure.

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Visually inspect
HO2S circuit for exposed wiring, water contamination, corrosion and proper installation. On some
applications, a hoist is required to access HO2S harness. Start engine and allow to idle. Using scan tool,
access suspect HO2S PIDs. HO2S DTC identification is as follows:

DTC P0132 refers to upstream HO2S-11.

DTC P0138 refers to downstream HO2S-12.

DTC P0152 refers to upstream HO2S-21.

DTC P0158 refers to downstream HO2S-22.

If HO2S PID voltage is 1.5 volt or more, go to next step. If HO2S PID voltage is less than 1.5 volt,
concern may be intermittent. Attempt to duplicate concern, perform wiggle test on suspect circuit harness
and component. If concern was duplicated, perform this system test again. If concern was not duplicated,
go to TEST Z, step 1).

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 111) to step 115). No test procedures have been omitted.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

HO2S may be displayed as O2S on scan tool.

2003 Ford Pickup F150

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

116) Check HO2S For Short To PWR Inside Of Sensor

Turn ignition switch to OFF position. Disconnect suspect HO2S connector. Turn ignition switch to ON
position. Using scan tool, access suspect HO2S PID. If HO2S PID voltage is .5 volt or more, go to next
step. If HO2S PID voltage is less than .5 volt, replace internally shorted HO2S sensor.

117) Check HO2S SIG Circuit For Short To PWR In Harness

Turn ignition switch to OFF position. Ensure suspect HO2S is disconnected. Disconnect PCM connector
(s). Using a DVOM, measure resistance between HO2S SIG circuit, and both VPWR and VREF circuits
at PCM harness connector. If all resistance measurements are more than 10 k/ohms, replace PCM. If any
resistance measurement is 10 k/ohms or less, repair short to PWR in affected circuits.

TEST HA: NATURAL GAS FUEL CONTROL

Diagnostic Aids

Perform this test when directed by QUICK TEST or if directed by other test procedures. This test is used to
diagnose:

HO2S Heater

Engine Vacuum Systems

Fuel Injector(s)

Wiring Harness Connector & Circuits; (HO2S HTR, INJ 1-8, VPWR & SIG RTN)

Powertrain Control Module (PCM)

Natural Gas (NG) Module

NGV HO2S PCM TERMINAL IDENTIFICATION

NOTE:

After each service or repair procedure has been completed, reconnect all
components. Clear DTCs and repeat QUICK TEST procedures to ensure all EEC-
V systems are working properly and DTCs are no longer present.

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 appropriate FUEL SYSTEM
PRESSURE RELEASE procedure under FUEL SYSTEM VENTING in
appropriate REMOVAL & INSTALLATION article.

Application

PCM Terminal No.

HO2S-11 SIG (Right Upstream)

HO2S-11 HTR (Right Upstream)

HO2S-12 SIG (Right Downstream)

HO2S-12 HTR (Right Downstream)

HO2S-21 SIG (Left Upstream)

2003 Ford Pickup F150

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

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