Ford F150 Pickup. Manual — part 1481

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Wiring Harness Circuits (TCSS & SIG RTN)

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Powertrain Control Module (PCM)

Fig. 198: Identifying TCSS Circuits & Connector Terminals (Escape 2.0L - M/T)
Courtesy of FORD MOTOR CO.

Fig. 199: Identifying VSS Circuits & Connector Terminals (All Others)
Courtesy of FORD MOTOR CO.

2003 Ford Pickup F150

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

Testing

1) For Continuous Memory Only DTC P0500, P0501 & P1502: Check VSS Circuits For Open In
Harness (VRS Type)
DTCs P0500, P0501and P1502 indicate that PCM has detected an error in vehicle speed information
received from Vehicle Speed Sensor (VSS), Transfer Case Speed Sensor (TCSS) or Anti-Lock Brake
System (ABS) module. Possible causes for this fault are:

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Open or short in VSS (+) or VSS (-) circuit.

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Open in TCSS signal or TCSS signal return circuit.

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Short to GND in VSS or TCSS circuit.

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Short to PWR in VSS or TCSS circuit.

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Open or short in VSC between PCM and appropriate control module.

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Faulty wheel speed sensor(s).

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Faulty wheel speed sensor(s) wiring harness.

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Faulty module(s) connected to vehicle speed circuit.

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Faulty transfer case, vehicle or wheel speed sensors.

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Faulty drive mechanism for VSS or TCSS.

Turn ignition switch to OFF position. Disconnect VSS connector. Disconnect PCM connector. Inspect
connectors for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure
resistance of VSS(+) and VSS (-) circuits between PCM harness connector and VSS harness connector.
See Fig. 198 and Fig. 199 . 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 affected VSS(+) or (-) circuit. Perform DRIVE
CYCLES. Ensure OBD-II DRIVE CYCLE is performed to verify repair.

2) Check VSS Circuits For Shorts To Ground Or Power In Harness

Using a DVOM, measure resistance between VSS(+) circuit, and PWR GND, VPWR and VSS(-) circuits
at PCM harness connector. See WIRING DIAGRAMS. See Fig. 198 and Fig. 199 . If all resistance
measurements are more than 5 ohms, go to next step. If any resistance measurement is 5 ohms or less, go
to step .

3) Check VSS Resistance

Using a DVOM, measure resistance between VSS terminals. If resistance is not 170-270 ohms, replace
VSS. If resistance is 170-270 ohms, replace PCM.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 4) to step 15). No test procedures have been omitted.

2003 Ford Pickup F150

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

4) Verify If VSS Circuit Is Shorted In Harness Or Another Module
Determine which, if any, modules are connected to the VSS circuit. See WIRING DIAGRAMS. If no
other modules are connected to the VSS circuit, repair short circuit. Perform DRIVE CYCLES. Ensure
OBD-II DRIVE CYCLE is performed to verify repair. If other modules are connected, one at a time,
disconnect the modules associated with the VSS circuit. After disconnecting each module, again test for
short circuit. Repeat until each associated module has been disconnected or the short circuit has been
eliminated. If the short circuit remains after all associated modules were disconnected, repair short circuit
in appropriate VSS circuit. Perform DRIVE CYCLES. Ensure OBD-II DRIVE CYCLE is performed to
verify repair. If short is associated with a connected module, see appropriate diagnostic article for that
module.

15) For KOER Only DTC P1501: Check PCM VSS PID For Input Signal
This DTC indicates VSS input signal was detected by PCM during self-test. A DTC P1501 will be stored
and self-test will abort when this occurs. Noisy VSS input signal from Radio Frequency Interference
(RFI) or Electromagnetic Interference (EMI) external source (i.e.; ignition wires, charging circuits, etc.)
can be possible causes for this fault.

Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Using scan tool, access
VSS PID from PID/DATA MONITOR & RECORD menu and observe vehicle speed input to PCM.
While observing VSS PID, increase engine speed to 2000 RPM and return to idle several times. If VSS
PID reading is 3 MPH or more, go to step 22). If VSS PID value is less than 3 MPH, fault cannot be
duplicated at this time. Clear DTCs and repeat QUICK TEST. If DTC P1501 is still present, go to TEST
Z, step 1).

20) For Continuous Memory Only DTC P0503 & P1500: Check For Intermittent Fault
This DTC indicates poor or noisy VSS performance. Possible causes for this fault are:

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Noisy TCSS/VSS Input Signal From Radio Frequency Interference (RFI) or Electromagnetic
Interference (EMI) (Ignition Wires, Charging Circuits, Etc.)

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Faulty VSS Or Driven Gears

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Faulty TCSS

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Damaged Wiring Harness Or Connectors

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Faulty Module Or Circuit Connected To TCSS/VSS

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Aftermarket Add-On Accessories

Turn ignition switch to OFF position. Disconnect VSS sensor. Visually inspect VSS and VSS circuits for
potential faults as follows:

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Loose VSS Circuit Connectors

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 15) to step 20). 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

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Loose VSS Circuit Connector Terminals

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Damaged VSS Wiring Harness Insulation

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Incorrect VSS Circuit Routing

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Incorrect VSS Installation

If no faults are found, go to next step. If faults are found, repair as necessary. Perform DRIVE CYCLES.
Ensure OBD-II DRIVE CYCLE is performed to verify repair.

21) Check PCM VSS PID For Input Signal

Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Using scan tool,
access VSS PID from PID/DATA MONITOR & RECORD menu. Test drive vehicle at several steady
speeds at more than, and less than 30 MPH.

During each steady state speed, check for VSS PID variations of plus or minus 5 MPH for more than 10
seconds. If any variations occur, go to next step. If variations do not occur, fault cannot be duplicated at
this time. Testing is complete.

22) Check VSS Harness Routing

Visually inspect VSS wiring harness. Ensure wiring is not routed near high current wires such as ignition
wires or charging system wires. Verify VSS wiring harness is shielded and grounded (if applicable).
Check VSS wiring harness resistance. Refer to Fig. 199-Fig. 201 to check VSS circuits. If faults are
found, repair as necessary. If no faults are found, fault cannot be duplicated at this time. Go to TEST Z,
step 1) and check for intermittents.

30) For Continuous Memory Only DTCs P0500 & P1502: Visual Inspection
DTCs indicates the Powertrain Control Module (PCM) detected an error in the vehicle speed information.
Vehicle speed data is received from either the Vehicle Speed Sensor (VSS), Transfer Case Speed Sensor
(TCSS) or Anti-Lock Brake System (ABS) control module. If the engine RPM is above the torque
converter stall speed (automatic transmission) and engine load is high, it can be inferred that the vehicle
must be moving. If there is insufficient vehicle speed data input, a malfunction is indicated and a DTC is
set. On most vehicle applications, the Malfunction Indicator Lamp (MIL) will be triggered when this
DTC is set. Possible causes are:

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Open in VSS+/VSS- harness circuit.

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Open in TCSS signal or TCSS signal return harness circuit.

NOTE:

On scan tools with Data Record feature, record data for playback to help
identify variations.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips
from step 22) to step 30). 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