Inspection Procedure 1: Check the hands free-ECU power supply circuit. <Vehicles with radio and CD player>
caution
Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
CIRCUIT OPERATION
The hands free-ECU is energised via the fusible link.
The ACC signal is received through the radio and CD player.
PROBABLE CAUSES
Malfunction of the hands free-ECU
Malfunction of the radio and CD player
Damaged harness wires and connectors
DIAGNOSIS PROCEDURE
STEP 1. Resistance measurement at hands free-ECU connector (GND terminal).
(1)Disconnect hands free-ECU connector, and measure at the wiring harness side.
(2)Check the continuity between GND terminal and earth. OK: Continuity exists (2 Ω or less)
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).
(1)Disconnect hands free-ECU connector, and measure at the wiring harness side.
(2)Measure the voltage between +B terminal and body earth. OK: System voltage
Q.
Is the check result normal?
Go to Step 5
Go to Step 4
STEP 4. Check of short to power supply, 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).
(1)Disconnect hands free-ECU connector, and measure at the wiring harness side.
(2)Turn the ignition switch to "ACC" position.
(3)Measure the voltage between ACC terminal and body earth. OK: System voltage
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 connector.