Inspection Procedure
16: Engine-ECU Power Supply System
OPERATION
- The battery voltage is applied to the engine control relay connector terminal.
- The engine-ECU connector terminal C/R makes the power transistor in the unit be
in "ON" position and makes currents go on the engine control relay coil, and that makes the
relay be in "ON" position.
- When the engine control relay is in "ON" position, the battery voltage is supplied
to the engine-ECU connector terminal BAT1 and terminal BAT2, the sensor and the actuator from
the engine control relay connector terminal.
- The engine-ECU connector terminal GNDB, terminal GNDE and terminal SGND is earthing
to the vehicle body.
FUNCTION
- When the ignition switch ON signal is input into the engine-ECU via ETACS-ECU,
the engine-ECU turns ON the engine control relay. This causes battery voltage to be supplied
to the engine-ECU, sensor and actuator.
PROBABLE CAUSES
- Failed battery
- Failed engine control relay
- Failed ignition switch <Vehicles without KOS>
- Failed OSS-ECU <Vehicles with KOS>
- Open/short circuit or harness damage in engine control relay circuit, or loose connector
contact.
- Open/short circuit or harness damage in ignition switch (IG1) circuit, or loose
connector contact.
- Open circuit or harness damage in engine-ECU earth circuit, or loose connector contact.
- Failed ETACS-ECU
- Failed engine-ECU
|
|
- Battery check (Refer to GROUP 54A - Battery - On-vehicle Service - Battery
Test
 ).
|
|
|
Q.
Is the check result normal?
|
|
|
 Go to Step 2.
|
|
|
|
|
|
 Replace the battery.
|
|
|
|
|
|
STEP 2. Check engine control relay itself.
|
|
|
- Engine control relay continuity check (Refer to ).
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 3.
|
|
|
|
|
|
Replace the engine control relay.
|
|
|
|
|
|
STEP 3. Voltage measurement at engine control relay connector (power
supply lines).
|
|
|
(1)Remove relay, and measure at relay box side.
|
|
|
(2)Check the voltage between the engine control relay connector (power supply lines)
and body earth.
OK: System voltage
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 4.
|
|
|
|
|
|
Repair power supply lines between battery
and engine control relay connector.
|
|
|
|
|
|
STEP 4. Voltage measurement at engine-ECU connector (C/R terminal).
|
|
|
(1)Disconnect the connector, and measure at the wiring harness side.
|
|
|
(2)Check the voltage between the engine-ECU connector (C/R terminal) and body earth.
OK: System voltage
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 5.
|
|
|
|
|
|
Repair C/R line between engine control relay connector
and engine-ECU connector.
|
|
|
|
|
|
STEP 5. Voltage measurement at engine-ECU connector (BAT1, BAT2 terminal).
|
|
|
(1)Disconnect the connector, and measure at the wiring harness side.
|
|
|
(2)Short-circuit engine-ECU connector terminal C/R to the body earth.
|
|
|
(3)Check the voltage between the engine-ECU connector (BAT1, BAT2 terminal) and body
earth.
OK: System voltage
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 8.
|
|
|
|
|
|
Go to Step 6.
|
|
|
|
|
|
STEP 6. Check of open circuit and short to earth in BAT1, BAT2 line
between engine control relay connector and engine-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 7.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 7. Check of damage in power supply line between battery connector
and engine control relay connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Repair C/R line between engine control relay connector
and engine-ECU connector.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 8. Check of damage in BAT1, BAT2 line between engine control
relay connector and engine-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 9.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 9. Check of damage in power supply line between battery and engine
control relay connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 10.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 10. Voltage measurement at engine-ECU connector (IGN terminal).
|
|
|
(1)Disconnect the connector, and measure at the wiring harness side.
|
|
|
(3)Check the voltage between the engine-ECU connector (IGN terminal) and body earth.
OK: System voltage
|
|
|
Q.
Is the check result normal?
|
|
|
YES  : Go to Step 15 <Vehicles without KOS>.
|
|
|
|
|
|
YES : Go to Step 16 <Vehicles with KOS>.
|
|
|
|
|
|
Go to Step 11.
|
|
|
|
|
|
STEP 11. Voltage measurement at ETACS-ECU connector (IG1 terminal).
|
|
|
(1)Disconnect the connector, and measure at the wiring harness side.
|
|
|
(3)Check the voltage between the ETACS-ECU connector (IG1 terminal) and body earth.
OK: System voltage
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 14.
|
|
|
|
|
|
NO : Go to Step 12 <Vehicles without KOS>.
|
|
|
|
|
|
NO : Go to Step 13 <Vehicles with KOS>.
|
|
|
|
|
|
STEP 12. Check ignition switch itself.
|
|
|
- Check ignition switch itself (Refer to GROUP 54A - Ignition Switch - Ignition
Switch - Ignition Switch Check).
|
|
|
Q.
Is the check result normal?
|
|
|
Repair IG1 line between ignition switch connector
and ETACS-ECU connector.
|
|
|
|
|
|
Replace the ignition switch.
|
|
|
|
|
|
STEP 13. Check of open circuit and short to earth in IG1 line between
OSS-ECU connector and ETACS-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Perform troubleshooting of OSS System (Refer to GROUP 42B - Troubleshooting <OSS-ECU> - Trouble
Symptom Chart).
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 14. Continuity check on ETACS-ECU connectors
|
|
|
(1)Disconnect connectors, and measure at the ETACS-ECU side.
|
|
|
(2)Continuity test between terminal IG1 and IGN.
| note |
Connect the (+) side of circuit tester to terminal IGN.
|
OK: Continuity
|
|
|
Q.
Is the check result normal?
|
|
|
Repair IGN line between ETACS-ECU connector
and engine-ECU connector.
|
|
|
|
|
|
Replace the ETACS-ECU.
|
|
|
|
|
|
STEP 15. Check of damage in IG1 line between ignition switch connector
and ETACS-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 17.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 16. Check of damage in IG1 line between OSS-ECU connector and
ETACS-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 17.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 17. Continuity check on ETACS-ECU connectors
|
|
|
(1)Disconnect connectors, and measure at the ETACS-ECU side.
|
|
|
(2)Continuity test between terminal IG1 and IGN.
| note |
Connect the (+) side of circuit tester to terminal IGN.
|
OK: Continuity
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 18.
|
|
|
|
|
|
Replace the ETACS-ECU.
|
|
|
|
|
|
STEP 18. Check of damage in IGN line between ETACS-ECU connector and
engine-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 19.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 19. Check of open circuit and damage in GNDB, GNDE, SGND line
between engine-ECU connector and body earth.
|
|
|
Q.
Is the check result normal?
|
|
|
Replace the engine-ECU.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|