Test Procedure

B1 CHECK THE B+ AND IGN START/RUN VOLTAGE TO PCM POWER RELAY

PCMPWR Relay connector disconnected.
Key ON Engine OFF.
Measure the voltage between:

( + )PCMPWR Relay Connector, Harness Side	( - )
B+	Ground
IGN START/RUN	Ground

Are the voltages greater than 10.5 V?

Yes	No
GO to B2.	KEY OFF. REPAIR open circuit. There is a B+ or IGN START/RUN circuit fault. CHECK the condition of the related fuse(s)/diode. If OK, REPAIR the open circuit. If the fuse is damaged, check the IGN START/RUN or B+ and VPWR circuits for a short to ground before replacing.

B2 CHECK THE GROUND CIRCUIT TO THE PCM POWER RELAY"

Measure the voltage between:

( + )PCMPWR Relay Connector, Harness Side	( - )PCMPWR Relay Connector, Harness Side
B+	GND

Is the voltage greater than 10.5 V?

Yes	No
GO to B3.	KEY OFF. REPAIR open circuit.

B3 CHECK FOR AN OPEN VPWR CIRCUIT BETWEEN THE PCM AND POWER RELAY

PCM connector disconnected.
Measure the resistance between:

( + )PCMPWR Relay Connector, Harness Side	( - )PCM Connector, Harness Side
PWR	VPWR

Is the resistance less than 5 ohms?

Yes	No
INSTALL a new PCMPWR relay.	REPAIR open circuit.

B4 CHECK FOR VEHICLES THAT HAVE 2 PCM POWER RELAYS

NOTE: The PCM power relay No. 2 (also referred to as the COPS and HO2S relay) supplies VPWR to two separately fused circuits. REFER to the appropriate SYSTEM WIRING DIAGRAMS article to determine fuse locations.

Fig 1: Identifying Power Relay 2 Power Out Circuit

Courtesy of FORD MOTOR CO.

Inspect the VPWR circuit fuse that goes to the component where the VPWR check failed.

Is the fuse OK?

Yes	No
GO to B5.	INSTALL a new Component: Fuse. CHECK the VPWR for shorts to ground

B5 CHECK FOR VPWR TO BOTH FUSES CONNECTED TO THE PCMPWR-2 RELAY

Key ON Engine OFF.
Measure the voltage between:

( + )Component: Fuse Connector, Harness Side	( - )
VPWR	Ground

Remove and inspect the other VPWR circuit fuse that goes to the components supplied by the PCMPR No. 2. Repair as necessary.
Measure the voltage between:

( + )Component: Fuse Connector, Harness Side	( - )
VPWR	Ground

Is the voltage to both fuses greater than 10.5 volts?

Yes	No
REPAIR open circuit. (The open circuit is between the fuse and the component where the VPWR check failed)	KEY OFF. If only 1 voltage is less than 10.5 volts, repair the open circuit between the fuse and the splice. Otherwise, GO to B6.

B6 CHECK VPWR CIRCUIT CONTINUITY BETWEEN THE FUSE AND PCM POWER RELAY NO. 2

PCMPWR-2 Relay connector disconnected.
Measure the resistance between:

( + )PCMPWR-2 Relay Connector, Harness Side	( - )Component: Fuse Connector, Harness Side
VPWR - Pin	5 FUSE

Is the resistance less than 5 ohms?

Yes	No
GO to B7.	REPAIR open circuit. (The open is between the splice and the PCMPWR-2 relay)

B7 CHECK THE B+ AND IGN START/RUN VOLTAGE TO PCMPWR-2

Key ON Engine OFF.
Measure the voltage between:

( + )PCMPWR-2 Relay Connector, Harness Side	( - )
B+ - Pin 3	Ground
IGN START/RUN - Pin 2	Ground

Are the voltages greater than 10.5 V?

Yes	No
GO to B8.	KEY OFF. REPAIR open circuit. There is a B+ or IGN START/RUN circuit fault. CHECK the condition of the related fuse(s)/diode. If OK, REPAIR the open circuit. If the fuse is damaged, check the IGN START/RUN or B+ and VPWR circuits for a short to ground before replacing.

B8 CHECK THE PCMPWR-2 GND CIRCUIT FOR AN OPEN IN THE HARNESS

Measure the voltage between:

( + )PCMPWR-2 Relay Connector, Harness Side	( - )PCMPWR-2 Relay Connector, Harness Side
B+ - Pin 3	GND - Pin 1

Is the voltage greater than 10.5 V?

Yes	No
INSTALL a new PCMPWR-2 relay.	KEY OFF. REPAIR open circuit.