Ford F150 Pickup. Instruction — part 1584

Fig. 371: Identifying Output Shaft Speed Sensor Circuits & Harness Connector Terminals (All Others)
Courtesy of FORD MOTOR CO.

Testing

1) For Continuous Memory Only DTCs P0720, P0721, P0722, P0723 & P1900: Verify Drive Cycle
DTC P0720 is set when PCM detects insufficient input signal from OSS sensor. DTC P0721 is set when
PCM detects noise interference on OSS sensor signal. DTC P0722 is set when PCM detects missing OSS
sensor signal. DTCs P0723 and P1900 are set when PCM detects irregular or interrupted OSS sensor
signal. Possible causes are:

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OSS Sensor Circuit Open, or Shorted To GND or PWR

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Wiring Misrouted, Damaged Or Insulation Worn

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After Market Add-On

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Harness Intermittently Shorted Or Open, Connector Damaged Or Not Properly Seated

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Faulty Or Incorrectly Installed OSS Sensor

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Faulty PCM

Using scan tool, access OSS PID from PID/DATA MONITOR & RECORD menu. Road test vehicle and
observe OSS PID. Ensure transmission shifts through all gear ranges, up and down. If OSS PID value
increases and decreases with engine and vehicle speed, go to next step. If OSS PID value does not
increase and decrease with engine and vehicle speed, perform the following:

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On Focus 2.0L M/T, go to step 3).

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On all others, go to step 5).

2) Visual Inspection

Turn ignition switch to OFF position. Disconnect OSS sensor connector located on side of transmission.
Inspect connector for loose, damaged or corroded terminals. Repair as necessary. If connector is okay,
fault is unable to be duplicated at this time. Go to TEST Z, step 1) and check for intermittent faults.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

2003 Ford Pickup F150

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

3) Check VPWR To OSS Sensor

Turn ignition switch to OFF position. Disconnect OSS sensor connector. Turn ignition switch to ON
position. Using a DVOM, measure voltage between chassis ground and VPWR circuit at OSS sensor
harness connector. See Fig. 370. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts
or less, repair open in OSS circuit.

4) Check PWR GND To OSS Sensor

Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance between negative
battery terminal and PWR GND circuit at OSS sensor harness connector. If resistance is less than 5 ohms,
go to next step. If resistance is 5 ohms or more, repair open in PWR GND circuit.

5) Check OSS Circuit For Short To VPWR

Disconnect OSS sensor connector, if not done previously. Turn ignition switch to ON position. Using a
DVOM, measure voltage between negative battery terminal and OSS circuit at OSS sensor harness
connector. See Fig. 366-Fig. 371 . If voltage is less than one volt, go to next step. If voltage is one volt or
more, repair short to VPWR in OSS circuit.

6) Check OSS & SIG RTN Circuits For Open In Harness

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose,
damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of OSS and SIG
RTN circuits between PCM harness connector and OSS sensor harness connector. 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 OSS or SIG RTN circuit.

7) Check OSS Circuit For Short To SIG RTN Circuit Or Chassis Ground

Using a DVOM, measure resistance between OSS circuit, and SIG RTN circuit at OSS sensor harness
connector and chassis ground. If either resistance measurement is 10 k/ohms or less, repair OSS circuit
for short to chassis ground or SIG RTN circuit. If both resistance measurements are more than 10 k/ohms,
perform the following:

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On Focus 2.0L M/T, go to step 9).

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On all others, go to next step.

8) Check Resistance Of OSS Sensor

Using a DVOM, measure resistance between OSS sensor terminals. If resistance is 450-1250 ohms,
replace PCM. If resistance is not 450-1250 ohms, replace OSS sensor.

9) Check OSS Signal Output To PCM (3-Wire OSS Sensor)

Raise and support front of vehicle so that front wheels can rotate freely. Turn ignition switch to ON
position and place gearshift lever in Neutral. Using a DVOM, measure voltage between OSS and PWR

2003 Ford Pickup F150

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

GND circuits at PCM harness connector while rotating one wheel with opposite wheel held stationary.
See Fig. 370. If OSS sensor output voltage pulses from less than one volt to more than 5 volts, replace
PCM. If voltage does not pulse as specified, replace OSS sensor.

TEST X: CONSTANT CONTROL RELAY MODULE

Diagnostic Aids

CCRM interfaces with the EEC-V system to provide control for A/C clutch, cooling fan and Fuel Pump Driver
Module (FPDM). CCRM also contains EEC-V power relay, which provides vehicle power (VPWR) to
Powertrain Control Module (PCM) and EEC-V system. Perform this test only when instructed by QUICK
TEST or if directed by a system test. This test is only intended to diagnose the following:

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Constant Control Relay Module (CCRM)

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Harness Circuits (B+, FC, LFC, HFC, ACCS, WAC, VPWR (To CCRM), A/C CLUTCH PWR, LOW
FAN PWR, HIGH FAN PWR & GND). See Fig. 372-Fig. 374.

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Powertrain Control Module (PCM)

To prevent replacing good components, be aware the following non-EEC related components or systems may
be at fault:

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A/C System

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Fuel System

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Starting & Charging System

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.

2003 Ford Pickup F150

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

Fig. 372: Identifying Constant Control Relay Module Circuits (Mustang 3.8L)
Courtesy of FORD MOTOR CO.

2003 Ford Pickup F150

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