On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

B: Electronic Engine Control (EC) Power Relay

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	No
RECONNECT IAC valve. GO to B2 .	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	No
GO to B3 .	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	No
REPLACE power relay.	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?

Yes	No
GO to B6 .	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	No
REPAIR open circuit between fuse and component where VPWR check failed.	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 of either fuse.

Is resistance less than 5.0 ohms?

Yes	No
GO to B2 . Make all indicated checks at power relay #2.	REPAIR open VPWR circuit between splice and power relay #2.