ECM Power and Ground Supply Circuits

CONTROL RELAY AND IGNITION SWITCH-IG






When the ignition switch is turned on, battery voltage is applied from the ignition switch to the ECU. This is turns ON the power transistor and energizes the control relay coil. This turns ON the control relay switch and power is supplied from the battery to the ECU through the control relay switch.

Control Relay And Ignition Switch-IG Circuit:

CONTROL RELAY AND IGNITION SWITCH-IG CIRCUIT











HARNESS INSPECTION PROCEDURES






CONTROL RELAY INSPECTION

NOTE: When applying battery voltage directly, make sure that it is applied to correct terminal Otherwise, the relay could be damaged.











1. Connect a 12V power supply (+) terminal to the terminal 6of the control relay and measure the voltages at terminals 2 and 1 when the (-) terminal is connected to and disconnected from the terminal 8.











2. Connect a 12V power supply (-) terminal to the terminal 10 of the control relay and check the continuity between terminals 3 and 4 when the (+) terminal is connected to and disconnected from the terminal 7.











3. Connect a 12V power supply (+) terminal to the terminal 3 of the control relay and measure the voltages at the terminal 4 when the (-) terminal is connected to and disconnected from the terminal 9.
4. If one of the above is improper, replace the 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.