Inspection Procedure 1: Check the DC/DC converter power supply circuit.


caution Even when the diagnosis code No. B1301 or B1302 is set in the AS&G-ECU, do not conclude as a DC/DC converter or AS&G-ECU error, and be sure to check the DC/DC converter power supply circuit.

CIRCUIT OPERATION



  • The power supply to the DC/DC converter is provided by the fusible link (36) <Petrol> or (38) <Diesel>.
  • The ACC signal is received C-12 DC/DC converter connector terminal No.6 from C-415 ETACS-ECU connector terminal No.9.

PROBABLE CAUSES



  • The DC/DC converter connector may be defective.
  • The battery may be defective.
  • Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. Battery test
Check the battery state. (Refer to .)

Q. Is the check result normal?
Go to Step 2.
Replace the battery.

STEP 2. M.U.T.-III ETACS system data list
Check the input signal of ACC relay.

  • Turn the ignition switch to the ACC position.
Item No.
 Item name
 Normal condition
Item 288
 ACC switch
 ON
OK: Normal condition is displayed.

Q. Is the check result normal?
Go to Step 3.
Refer to ETACS - Input Signal Procedure 1 "The ignition switch (ACC) signal is not sent to the ETACS-ECU" .

STEP 3. Connector check: C-12 DC/DC converter connector and C-415 ETACS-ECU connector

Q. Is the check result normal?
Go to Step 4.
Repair the defective connector.

STEP 4. Voltage measurement at C-12 DC/DC converter connector.
(1)Disconnect C-12 DC/DC converter connector, and measure at the wiring harness side.
(2)Turn the ignition switch to "ACC" position.
(3)Measure the voltage between terminal No.6 and body earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 5.
Go to Step 6.

STEP 5. Check the harness wire between C-415 ETACS connector terminal No.9 and C-12 DC/DC converter connector terminal No.6.

  • Check the signal line for open circuit and short circuit.
note Prior to the wiring harness inspection, check C-231 joint connector and C-127 intermediate connector, and repair if necessary.

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 wiring harness.

STEP 6. Voltage measurement at C-12 DC/DC converter connector.
(1)Disconnect C-12 DC/DC converter connector, and measure at the wiring harness side.
(2)Measure the voltage between terminal No.9 and body earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 8.
Go to Step 7.

STEP 7. Check the wiring harness between C-12 DC/DC converter connector terminal No.9 and fusible link (36) <Petrol> or (38) <Diesel>.

  • Check the power supply line for open circuit and short circuit.

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 wiring harness.

STEP 8. Resistance measurement at C-12 DC/DC converter connector.
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Check the continuity between terminal No.10 and earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
No action is necessary and testing is complete.
Go to Step 9.

STEP 9. Check the wiring harness between C-12 DC/DC converter connector terminal No.10 and body earth.

  • Check the body earth wires for open circuit.

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 wiring harness.