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.

Q. Is the check result normal?
Replace the radio and CD player.
Repair the connector(s) or wiring harness.