Ford F150 Pickup. Instruction - part 1460

This system test is only intended to diagnose the following components and circuits:  

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Vehicle Wiring Harness Circuits: Vehicle Power (VPWR), IGN START/RUN, Battery Positive Voltage 
(B+) & PCM Power Relay Ground  

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PCM Power Relay  

Testing 

1) VPWR Check At Fuel Injector Failed In Test C: Check For Open VPWR Circuit 
 
Turn ignition switch to OFF position. Disconnect fuel injector harness connector. Disconnect scan tool. 
Disconnect PCM power relay (PCM power relay No. 1 on LS and Thunderbird). Using a DVOM, 
measure resistance of VPWR circuit between fuel injector harness connector and PCM power relay 
cavity. See Fig. 168-Fig. 170 . If resistance is less than 5 ohms, reconnect fuel injector and go to next 
step. If resistance is 5 ohms or more, repair open in VPWR circuit between PCM power relay and fuel 
injector. 

Fig. 168: Identifying Power Relay Circuits (Escape, Focus, Sable & Taurus) 
Courtesy of FORD MOTOR CO. 

 

2003 Ford Pickup F150 

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

  

Fig. 169: Identifying Power Relay Circuits (LS & Thunderbird) 
Courtesy of FORD MOTOR CO. 

Fig. 170: Identifying Power Relay Circuits (All Others)

 

2003 Ford Pickup F150 

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

  

Courtesy of FORD MOTOR CO. 

2) Check B+ & IGN START/RUN Voltage To PCM Power Relay 
 
Ensure ignition switch is turned to OFF position and PCM power relay is disconnected. Using a DVOM, 
measure voltage between negative battery terminal and B+ terminal at PCM power relay cavity. Record 
voltage measurement. Turn ignition switch to ON position. Using a DVOM, measure voltage between 
negative battery terminal and IGN START/RUN terminal at PCM power relay cavity. If both voltage 
measurements are more than 10.5 volts, go to next step. If either voltage measurement is 10.5 volts or 
less, turn ignition switch to OFF position. Check B+ or IGN START/RUN circuits for open. Check 
condition of related fuse(s) or diode. If okay, repair open in affected circuit. If fuse is blown, check IGN 
START/RUN or B+ and VPWR circuits for short to ground before replacing fuse. 

3) Check Ground Circuit To PCM Power Relay 
 
Using a DVOM, measure voltage between chassis ground terminal and B+ terminal at PCM power relay 
cavity. If voltage is more than 10.5 volts, replace PCM power relay. If voltage is 10.5 volts or less, repair 
open in ground circuit. 

5) LS & Thunderbird VPWR Check Failed: Check Fuse 
Remove and inspect suspect VPWR fuse to component where VPWR check failed. If suspect fuse is 
okay, go to next step. If suspect fuse is blown, check VPWR circuit for short to ground between blown 
fuse and appropriate component. Repair as necessary and replace VPWR fuse. 

6) Check For Power To Other VPWR Circuit Fuse Connected To PCM Power Relay No. 2 
 
Remove and inspect other VPWR circuit fuse that goes to components supplied by power relay No. 2. 
Replace fuse as necessary. Turn ignition switch to ON position. Using a DVOM, measure voltage 
between negative battery terminal and both VPWR circuit fuse harness connectors from PCM power 
relay No. 2. If both voltage measurements are more than 10.5 volts, repair open between fuse and 
component where VPWR check failed. If both voltages are 10.5 volts or less, turn ignition switch to OFF 
position and go to next step. If only one measurement is 10.5 volts or less, repair open in VPWR circuit 
between fuse and splice. 

7) Check VPWR Circuit Continuity Between Fuse & PCM Power Relay No. 2 
 
Disconnect PCM power relay No. 2. Using a DVOM, measure resistance of VPWR circuit between PCM 
power relay No. 2 and either fuse harness connector. If resistance is less than 5 ohms, return to step 2) 
and perform checks for PCM power relay No. 2. If resistance is 5 ohms or more, repair open in VPWR 

NOTE:

A break in step numbering sequence occurs at this point. Procedure skips 
from step 3) to step 5). No test procedures have been omitted.

NOTE:

PCM power relay No. 2 (also referred to as COPS and HO2S relay) supplies 
VPWR to 2 separately fused circuits. To determine fuse locations, see 
WIRING DIAGRAMS.

 

2003 Ford Pickup F150 

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

  

circuit between PCM power relay No. 2 and splice. 

TEST C: REFERENCE VOLTAGE 

Diagnostic Aids 

SIG RTN is a dedicated ground used by most EEC-V system sensors. VREF is a 5-volt reference voltage that is 
continuously output by PCM. This consistent voltage signal is used on all 3-wire sensors. This system test is 
only intended to diagnose the following components and circuits:  

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Sensor harness circuits: SIG RTN, VREF, ETCREF and ETCRTN.  

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3-wire sensors: Throttle Position (TP)/(ETC TP) sensor, differential pressure feedback EGR sensor, A/C 
Pressure (ACP) sensor, Fuel Tank Pressure (FTP) sensor, Power Steering Pressure (PSP) sensor, Fuel 
Rail Pressure (FRP) sensor and Barometric (BARO) sensor, Swirl Control Valve Monitor (SCVM) 
sensor, EGR System Module (ESM) sensor, Temperature Manifold Absolute Pressure (TMAP) sensor, 
and Accelerator Pedal Position (APP) sensor.  

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Powertrain Control Module (PCM).  

Testing 

1) Check VREF Circuit For Short To PWR In Harness 
 
Disconnect TP sensor connector. Turn ignition switch to ON position. Using a DVOM, measure voltage 
between SIG RTN and VREF circuit terminals at TP sensor harness connector. See Fig. 163-Fig. 166 . If 
VREF voltage is more than 6 volts, check for short to PWR in VREF. Go to step 35). If VREF voltage is 
6 volts or less, go to next step. 

2) Check Battery Voltage 
 
Using a DVOM, measure voltage between battery terminals. If battery voltage is more than 10.5 volts, go 
to next step. If battery voltage is 10.5 volts or less, check charging system and battery and repair as 
necessary. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING 
SYSTEMS. Recharge or replace battery as necessary. 

3) Check Voltage Between B+ & SIG RTN Circuit 
 
Disconnect suspect sensor harness connector. Using a DVOM, measure voltage between SIG RTN 
terminal at suspect sensor harness connector and positive battery terminal. If voltage measurement is 
more than 10.5 volts and within one volt of battery voltage, go to next step. If voltage is 10.5 volts or less, 
a SIG RTN/PWR GND fault is present. Go to step 25). 

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.

NOTE:

For 122 and 150 terminal PCM harness connectors, VPWR PID can be 

 

2003 Ford Pickup F150 

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