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Open Or Shorted LFC, MFC Or HFC Circuit
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Open VPWR Circuit (Or IGN START/RUN Circuit On Escape) To LFC, MFC Or HFC Relay
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Faulty LFC, MFC Or HFC Relay
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Faulty PCM
Turn ignition switch to OFF position. Remove appropriate fan control (LFC, MFC or HFC) relay. See
COOLING FAN RELAY LOCATIONS table. Turn ignition switch to ON position. Using a DVOM,
measure voltage between negative battery terminal and VPWR (IGN START/RUN on Escape) circuit at
appropriate fan control relay cavity. See Fig. 321-Fig. 330 . If voltage is more than 10.5 volts, go to next
step. If voltage is 10.5 volts or less, repair open in VPWR (or IGN START/RUN) circuit to appropriate
fan control relay.
2) Check For LFC, MFC Or HFC Circuit Cycling
Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition
switch to ON position. Connect a test light between VPWR (or IGN START/RUN) circuit and LFC,
MFC or HFC circuit at appropriate fan control relay cavity. See Fig. 321-Fig. 330 . Using scan tool,
access OUTPUT TEST MODE. See OUTPUT TEST MODE under ADDITIONAL SYSTEM
FUNCTIONS. Observe test light while commanding appropriate cooling fan speed (LFC, MFC or HFC)
ON and OFF. On Escape, Sable and Taurus, commanding low speed fan ON will also command medium
fan ON. If test light illuminates and then turns off when appropriate fan control relay is commanded,
replace faulty fan control relay. If test light does not illuminate and then turn off when appropriate fan
control relay is commanded, repeat this test step. If test light still does not illuminate and then turn off
when appropriate fan control relay is commanded, turn ignition switch to OFF position, remove test light
and go to next step.
3) Check LFC, MFC Or HFC Circuit For Short To PWR In Harness
Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose,
damaged or corroded terminals. Repair as necessary. Turn ignition switch to ON position. Using a
DVOM, measure voltage between negative battery terminal and LFC, MFC or HFC circuit at appropriate
fan control relay cavity. See Fig. 321-Fig. 330 . If voltage is less than one volt, go to next step. If voltage
is one volt or more, repair LFC, MFC or HFC circuit for short to PWR.
4) Check LFC, MFC Or HFC Circuit For Short To Ground In Harness
Turn ignition switch to OFF position. Disconnect scan tool from DLC. Using a DVOM, measure
resistance between negative battery terminal and LFC, MFC or HFC circuit at appropriate fan control
relay cavity. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair
LFC, MFC or HFC circuit for short to ground.
5) Check For Open LFC, MFC Or HFC Circuit
Using a DVOM, measure resistance of LFC, MFC or HFC circuit between PCM harness connector and
appropriate fan control relay cavity. See Fig. 321-Fig. 330 . If resistance is less than 5 ohms, replace
PCM. If resistance is 5 ohms or more, repair open in LFC, MFC or HFC circuit.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline