between chassis ground and PCM harness connector terminal No. 86 (Black/Yellow wire). If resistance is
more than 10 k/ohms, replace PCM. If resistance is 10 k/ohms or less, repair short to ground in
Black/Yellow wire. Recheck cooling fan operation.
154) Check LFC (Fan Braking) Relay
Turn ignition switch to OFF position. Remove LFC (fan braking) relay. See COOLING FAN RELAY
LOCATIONS table. If cooling fans stop operating, replace LFC (fan braking) relay. Recheck cooling fan
operation. If fans do not stop operating, go to step 156).
155) Check Circuit Light Blue wire For A Short To Ground.
Turn ignition switch to OFF position. Disconnect: PCM connector. Measure the resistance between PCM
connector No. 28 (Light Blue wire) and ground. If the resistance is greater than 10 k/ohms, go to next
step. If resistance is not greater than 10 k/ohms, install a new engine wiring harness. Test the system for
normal operation
156) Check Light Green/Violet & Red/Orange Wires At MFC (Resistor Relay) & For Short To
PWR
Remove MFC (resistor) relay. If cooling fans stop operating, repair short to PWR in Light Green/Violet
wire between MFC (resistor) relay and LFC (fan braking) relay. See WIRING DIAGRAMS. Recheck
cooling fan operation. If cooling fans do not stop operating, repair short to PWR in Red/Orange wire
between MFC (resistor) relay and cooling fans. See WIRING DIAGRAMS. Recheck cooling fan
operation.
162) Check Operation Of The Electric Cooling Fan
Using scan tool, command the cooling fan ON. If the cooling fan operates, cooling fan system is okay.
Go to appropriate symptom under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG,
FLEX-FUEL & GASOLINE article. If the cooling fan does not operate, go to next step.
163) Check The Cooling Fan Relay
Remove the electric cooling fan relay. Using a DVOM, measure resistance between specified relay
terminals. See MINI ISO RELAY RESISTANCE SPECIFICATIONS table. See Fig. 306. If relay
resistance is not as specified, replace electric cooling fan relay. If relay resistance is as specified, connect
2 jumper wires from positive battery terminal to relay terminals No. 30 and 85. Connect another jumper
from relay terminal No. 86 to chassis ground. Using a DVOM, measure voltage between relay terminals
No. 86 and 87. If battery voltage is not present at relay terminal No. 87, replace cooling fan relay.
Recheck cooling fan operation. If the cooling fan relay passed the component test, go to next step.
164) Check Voltage To The Cooling Fan Relay
Using a DVOM, measure the voltage between the cooling fan relay connector terminal No. 30
(Red/Black wire) harness side and ground. If the voltage is greater than 10 volts, go to next step. If the
voltage is 10 volts or less, repair Red/Black wire as necessary. Test the system for normal operation.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline