B: Electronic Engine Control (EC) Power Relay

B: Introduction See: B: Electronic Engine Control (EC) Power Relay - Introduction

B1 VPWR CHECK AT IAC VALVE FAILED IN PINPOINT TEST C: CHECK FOR OPEN VPWR CIRCUIT

• Idle air control (IAC) valve disconnected.
• Disconnect scan tool from DLC.
• Disconnect electronic engine control power relay (referred to here as "power relay").
• Measure resistance of VPWR circuit between IAC valve harness connector and power relay harness connector.

Is resistance less than 5.0 ohms?
Yes

• RECONNECT IAC valve. GO to B2

.

No

• REPAIR open VPWR circuit between the power relay and the splice

to the IAC valve.

B2 CHECK B+ AND IGN START/RUN VOLTAGE TO POWER RELAY

• Measure B+ circuit voltage at the power relay harness connector.
• Key on.
• Measure IGN START/RUN circuit voltage at power relay harness connector.

Are both voltages greater than 10.5 volts?
Yes

• GO to B3

.

No

• KEY OFF. B+ or IGN START/RUN circuit fault. CHECK condition

of related fuse(s)/diode. If OK, REPAIR open circuit. If fuse is damaged,
check IGN START/RUN or B+ and VPWR circuits for short to ground before replacing.

B3 CHECK GROUND CIRCUIT TO POWER RELAY

• Measure voltage between B+ and the ground circuits at the power relay harness connector.

Is voltage greater than 10.5 volts?
Yes

• REPLACE power relay.

No

• REPAIR open ground circuit.

B5 LS6/LS8 VPWR CHECK FAILED: CHECK FUSE

Note: The electronic engine control power relay #2 supplies VPWR to two separately fused circuits. Refer to the applicable Wiring Diagrams to determine fuse locations.

• Remove and inspect VPWR circuit fuse that goes to the component where VPWR check failed.

Is the fuse OK?

• GO to B6

.

No

• CHECK VPWR circuit for short to ground between fuse and applicable

component. REPAIR as necessary. REPLACE fuse.

B6 CHECK FOR POWER TO OTHER VPWR CIRCUIT FUSE CONNECTED TO POWER RELAY #2

• Remove and inspect other VPWR circuit fuse that goes to the components supplied by the power relay #2. Service as necessary.
• Key on, engine off.
• Measure voltage to both VPWR circuit fuse harness connectors supplied by the power relay #2.

Are both voltages greater than 10.5 volts?
Yes

• REPAIR open circuit between fuse and component where VPWR check

failed.

No

• If both voltages were less than 10.5 volts:
• KEY OFF. GO to B7

.

• If only one voltage was less than 10.5 volts:
• REPAIR open circuit between fuse and splice.

B7 CHECK VPWR CIRCUIT CONTINUITY BETWEEN FUSE AND POWER RELAY #2

• Disconnect power relay #2.
• Measure resistance of the VPWR circuit between the power relay #2 harness connector and the harness connector either fuse.

Is resistance less than 5.0 ohms?
Yes

• GO to B2

0. Make all indicated checks at power relay #2.

No

• REPAIR open VPWR circuit between splice and power relay #2.