Inspection Procedure
1: Check the hands free-ECU power supply circuit.
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Before replacing
the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit
are normal.
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CIRCUIT OPERATION
- The hands free-ECU is energised via the fusible link.
- The ACC signal is received through the radio and CD player or multivision display.
PROBABLE CAUSES
- Malfunction of the hands free-ECU
- Malfunction of the radio and CD player <Vehicles with radio and CD player>
- Malfunction of the multivision display <Vehicles with MMCS>
- Damaged harness wires and connectors
DIAGNOSIS PROCEDURE
STEP 1. Resistance measurement at hands free-ECU connector
(GND terminal).
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(1)Disconnect hands free-ECU connector, and measure at the wiring harness side.
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(2)Check the continuity between GND terminal and earth.
OK: Continuity exists (2 Ω or less)
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Q.
Is the check result normal?
Go to Step 3.
Go to Step 2.
STEP 2. Check of open circuit in GND line between hands free-ECU connector
and body earth.
Q.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction).
Repair the connector(s) or wiring harness.
STEP 3. Voltage measurement at hands free-ECU connector (+B
terminal).
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(1)Disconnect hands free-ECU connector, and measure at the wiring harness side.
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(2)Measure the voltage between +B terminal and body earth.
OK: System voltage
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Q.
Is the check result normal?
Go to Step 5.
Go to Step 4.
STEP 4. Check of short to earth, and open circuit in +B line
between fusible link and hands free-ECU connector.
Q.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction).
Repair the connector(s) or wiring harness.
STEP 5. Voltage measurement at hands free-ECU connector (ACC terminal).
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(1)Disconnect hands free-ECU connector, and measure at the wiring harness side.
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(2)Turn the ignition switch to "ACC" position.
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(3)Measure the voltage between ACC terminal and body earth.
OK: System voltage
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Q.
Is the check result normal?
Replace the hands free-ECU.
Go to Step 6.
STEP 6. Check of short to power supply, short to earth, and open circuit
in ACC line between hands free-ECU connector and radio and CD player or multivision display
connector.
Q.
Is the check result normal?
Replace the radio and CD player or multivision display.
Repair the connector(s) or wiring harness.