Ford F150 Pickup. Instruction - part 1561

34) Check For Open HIGH FAN PWR & LOW FAN PWR Circuits 
 
Using a DVOM, measure resistance of HIGH FAN PWR and LOW FAN PWR circuits between 
appropriate HFC or LFC relay cavity and appropriate cooling fan harness connector. See Fig. 321, Fig. 
325-Fig. 327 or Fig. 329 . If both resistance measurements are less than 5 ohms, go to next step. If either 
resistance measurement is 5 ohms or more, locate and repair open in affected circuit. Recheck cooling fan 
operation. 

35) Command Low Speed Fan ON & Check For Voltage To Cooling Fans 
 
Reinstall HFC and LFC relays. Ensure cooling fan connector(s) are disconnected. Turn ignition switch to 
ON position. Using scan tool, access OUTPUT TEST MODE. Command low speed fan ON. Using a 
DVOM, measure voltage between negative battery terminal and LOW FAN PWR circuit at cooling fan 
harness connector (either connector on models with 2 cooling fans). See Fig. 321-Fig. 327 or Fig. 329 . If 
voltage is more than 10 volts, replace HFC relay and go to step 37). If voltage is 10 volts or less, go to 
step 75) and follow procedure for low speed cooling fan inoperative. After repair, repeat step 75) and 
follow procedure for high speed cooling fan inoperative. 

37) Check Cooling Fan Ground Circuit 
 
Turn ignition switch to OFF position. Disconnect scan tool from DLC. Using a DVOM, measure 
resistance of GND circuit between negative battery terminal and cooling fan harness connector(s). If 
resistance is less than 5 ohms, replace inoperative cooling fan(s). If resistance is 5 ohms or more, locate 
and repair open in GND circuit. Recheck cooling fan operation. 

40) Determine Which Fan Speed Is Operational 
 
If high speed fan was inoperative in step 31), go to step 46). If low speed fan was inoperative in step 31), 
go to next step. 

41) Low Speed Fan Inoperative: Command Low Fan ON & Check Voltage To Cooling Fan 
 
Ensure ignition switch is in ON position, scan tool is in OUTPUT TEST MODE and low speed cooling 
fan commanded OFF. Disconnect appropriate cooling fan connector (both connectors on models with 2 
cooling fans). Using scan tool, command low speed fan ON. Using a DVOM, measure voltage between 
negative battery terminal and LOW FAN PWR circuit at appropriate cooling fan harness connector. See 
Fig. 321-Fig. 329 . If voltage is 10 volts or less, go to next step. If voltage is more than 10 volts, check 
GND circuit to appropriate cooling fan. If GND circuit is okay, replace cooling fan and recheck cooling 
fan operation. 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 35) to step 37). No test procedures have been omitted.

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 37) to step 40). No test procedures have been omitted.

 

2003 Ford Pickup F150 

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

  

42) Check B+ Voltage To LFC Relay 
 
Turn ignition switch to OFF position. Remove LFC relay (engine cooling fan relay on models with only 
one relay). See COOLING FAN RELAY LOCATIONS table. Using a DVOM, measure voltage 
between negative battery terminal and B+ circuit at LFC relay cavity. See Fig. 321-Fig. 329 . If voltage is 
more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check for B+ circuit fault. Check 
appropriate B+ circuit fuse to relay. See WIRING DIAGRAMS. If fuse is okay, check for open in B+ 
circuit to LFC relay. Repair as necessary. If fuse is blown, check B+ and LOW FAN PWR circuits for 
short to ground before replacing fuse. Repair as necessary. Recheck cooling fan operation. 

43) Check For Open LOW FAN PWR Circuit 
 
Using a DVOM, measure resistance of LOW FAN PWR circuit between LFC relay cavity and 
appropriate cooling fan harness connector(s). If resistance is less than 5 ohms, go to step 75). If resistance 
is 5 ohms or more, locate and repair open in affected circuit. Recheck cooling fan operation. 

46) High Speed Fan Inoperative: Command High Speed Fan ON & Check For Voltage To Cooling 
Fan 
 
Ensure ignition switch is in ON position, scan tool is in OUTPUT TEST MODE and high speed cooling 
fan commanded OFF. Disconnect appropriate cooling fan connector (both connectors on models with 2 
cooling fans). Using scan tool, command high speed fan ON. Using a DVOM, measure voltage between 
negative battery terminal and HIGH FAN PWR circuit at appropriate cooling fan harness connector. See 
Fig. 322-Fig. 324 or Fig. 329 . If voltage is 10 volts or less, go to next step. If voltage is more than 10 
volts, check GND circuit to cooling fan. If GND circuit is okay, replace cooling fan and recheck cooling 
fan operation. 

47) Check B+ Voltage To HFC Relay 
 
Turn ignition switch to OFF position. Remove HFC relay. See COOLING FAN RELAY LOCATIONS
table. Using a DVOM, measure voltage between negative battery terminal and B+ circuit at HFC relay 
cavity. See Fig. 322-Fig. 324 or Fig. 329 . If voltage is more than 10.5 volts, go to next step. If voltage is 
10.5 volts or less, check B+ circuit for fault. Check appropriate B+ circuit fuse. If fuse is okay, check for 
open in B+ circuit to HFC relay. Repair as necessary. If fuse is blown, check B+ and HIGH FAN PWR 
circuits for short to ground before replacing fuse. Repair as necessary. Recheck cooling fan operation. 

48) Check For Open HIGH FAN PWR Circuit 
 
Ensure ignition switch is in OFF position. Using a DVOM, measure resistance of HIGH FAN PWR 
circuit between HFC relay cavity and appropriate cooling fan harness connector. See Fig. 322-Fig. 324 or 
Fig. 329 . If resistance is less than 5 ohms, go to step 75). If resistance is 5 ohms or more, repair open in 
HIGH FAN PWR circuit. Recheck cooling fan operation. 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 43) to step 46). No test procedures have been omitted.

 

2003 Ford Pickup F150 

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

  

50) Low &/Or High Speed Cooling Fan Inoperative: Check For B+ Voltage To HFC & LFC Relays
Ensure ignition switch is in ON position, scan tool is in OUTPUT TEST MODE and cooling fan 
commanded OFF. Remove LFC and HFC relays. See COOLING FAN RELAY LOCATIONS table. 
Using a DVOM, measure voltage between negative battery terminal and B+ circuit at both LFC relay and 
HFC relay cavity. See Fig. 330. If both voltage measurements are more than 10.5 volts, go to next step. If 
either voltage measurement is 10.5 volts or less, check for B+ circuit fault. Check appropriate B+ circuit 
fuse. If fuse is okay, check for open in B+ circuit. Repair as necessary. If fuse is blown, check B+ and 
LOW or HIGH FAN PWR circuits for short to ground before replacing fuse. Repair as necessary. 
Recheck cooling fan operation. 

51) Check For Open Fan PWR Circuit, Fan Ground & Internal Fan Circuits 
 
Ensure ignition switch is in OFF position. Using a DVOM, measure resistance between negative battery 
terminal and FAN PWR circuit at both the LFC and HFC relay cavity. See Fig. 330. If both resistance 
measurements are less than 15 ohms, go to next step. If either resistance measurement is 15 ohms or 
more, go to step 56). 

52) Check FAN PWR Circuit For Short To Ground In Harness 
 
Disconnect both cooling fan harness connectors. Using a DVOM, measure resistance between chassis 
ground and FAN PWR circuit at cooling fan harness connector. If resistance is more than 10 k/ohms, go 
to next step. If resistance is 10 k/ohms or less, locate and repair short to ground in FAN PWR circuit. 
Recheck cooling fan operation. 

53) Check HFC & LFC Relay Operation 
 
Leave cooling fans disconnected. Reinstall HFC and LFC relays. Turn ignition switch to ON position. 
Using scan tool, access OUTPUT TEST MODE. See 

OUTPUT TEST MODE

 under ADDITIONAL 

SYSTEM FUNCTIONS. Perform appropriate relay test procedure: 

z

HFC Relay 
 
Using scan tool, command high speed fan ON. Wait 15 seconds. Using a DVOM, measure voltage 
between negative battery terminal and FAN PWR circuit at cooling fan harness connector (either 
connector). Voltage should be more than 10.5 volts. 

z

LFC Relay 
 
Using scan tool, command low speed fan ON. Using a DVOM, measure voltage between negative 
battery terminal and FAN PWR circuit at cooling fan harness connector (either connector). Voltage 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 48) to step 50). No test procedures have been omitted.

NOTE:

On models with 2 cooling fans, if one cooling fan is inoperative and the 
other cooling fan operates normally, go to step 70).

 

2003 Ford Pickup F150 

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

  

should be more than 10 volts.  

If both voltage measurements are as specified, replace cooling fan(s). If either voltage measurement is not 
as specified, note which fan speed is inoperative and go to step 75). 

56) Check For Open FAN PWR Circuit Between Cooling Fan, & HFC & LFC Relays 
 
Turn ignition switch to OFF position. Disconnect cooling fan connector (either connector). Using a 
DVOM, measure resistance of FAN PWR circuit between cooling fan harness connector and specified 
HFC and LFC relay cavity. See Fig. 330. If both resistance measurements are less than 15 ohms, go to 
next step. If either resistance measurement is 15 ohms or more, locate and repair open in FAN PWR 
circuit. If open is only between LFC relay and cooling fan, check fan dropping resistor in LOW FAN 
PWR circuit. See COOLING FAN RESISTOR LOCATIONS table. Recheck cooling fan operation. 

COOLING FAN RESISTOR LOCATIONS 

57) Check Cooling Fan Ground Circuit 
 
Using a DVOM, measure resistance between negative battery terminal and ground circuit at cooling fan 
harness connector. If resistance is less than 5 ohms, replace inoperative cooling fan(s). If resistance is 5 
ohms or more, locate and repair open in ground circuit. Recheck cooling fan operation. 

60) Low, Medium &/Or High Speed Cooling Fan Always Runs (No DTCs): Ensure Fan Is Not On 
Because Of A/C High Pressure Switch Input To PCM 
Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Start engine and 
allow to idle. Using scan tool, access ACP PID from PID/DATA MONITOR & RECORD menu. If ACP 
PID indicates CLOSED, PCM will operate cooling fan when A/C high pressure switch is "closed". Leave 
engine running and go to next step. If ACP PID does not indicate CLOSED, ACP input is correct. Go to 
step 151) to check secondary circuits to cooling fan (Sable and Taurus), or go to step 65) (all others). 

61) Check A/C High Pressure Switch (Normally Open Contacts) 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 53) to step 56). No test procedures have been omitted.

Application

Location

Windstar

In Engine Compartment, Between Battery & Left Headlight

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 57) to step 60). No test procedures have been omitted.

NOTE:

Perform test step 60) when directed from ELECTRIC COOLING FAN 
ALWAYS ON symptom under SYMPTOMS in TROUBLE SHOOTING - NO 
CODES - CNG, FLEX-FUEL & GASOLINE article.

NOTE:

A/C high pressure switch may also be referred to as dual pressure switch.

 

2003 Ford Pickup F150 

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