ECM Power and Ground Supply Circuits
Control Relay And Ignition Switch-IG Circuit:
KEY "ON" POWER CIRCUIT
1. Disconnect the negative battery cable and the ECU connector.
2. Reconnect the negative battery cable and turn the key to the ON position.
3. Using a volt meter, check for voltage between ECU harness connector terminal 6 and ground.
Voltage
System voltage.
4. Turn the key to the OFF position and disconnect the control relay.
5. Using a volt meter, check for voltage between relay harness connector terminal 3 and ground.
Voltage
System voltage.
6. Disconnect the negative battery cable and the ECU connector.
7. Using an ohm meter check for continuity between relay harness connector 4 and ECU harness connector 24.
Continuity
Should exist.
8. Using an ohm meter check for continuity between relay harness connector 9 and ECU harness connector 4.
Continuity
Should exist.
9. Using an ohm meter check for continuity between relay harness connector 9 and ground
Continuity
Should exist.
10. Using an ohm meter check for continuity between relay harness connector 4 and ground.
Continuity
Should not exist.
11. Using an ohm meter check for continuity between relay harness connector 9 and ground.
Continuity
Should not exist.
For CONTROL RELAY testing information refer to Control Relay.
Engine Control Unit (ECM) Ground Circuit:
GROUND CIRCUIT
1. Disconnect the ECU connector.
2. Using an ohm meter, check for continuity between ECU harness terminal 5 and ground.
Continuity
Should exist.
3. Using an ohm meter, check for continuity between ECU harness terminal 10 and ground.
Continuity
Should exist.
If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed, road test the vehicle to confirm that the repair has corrected the problem.
If the same problem reoccurs, it is possible that there is an intermittent failure of the component or the ECU. Check for looseness at all harness junctions and test for an intermittent failure.