Code No. B1354: DC/DC converter (Entertainment System) Control Circuit




OPERATION



  • At the auto start, the AS&G-ECU connector terminal DCCT sends increasing voltage request signal to the DC/DC converter (entertainment system) connector terminal DCCT.
  • If the increasing voltage control system is abnormal, the DC/DC converter (entertainment system) connector terminal DCCA sends a diagnostic signal to the AS&G-ECU connector terminal DCCA.

FUNCTION



  • The AS&G-ECU checks whether the increasing voltage control system is normal.

TROUBLE JUDGMENT


Check Condition
  • Ignition switch is "ON" position.
  • Battery voltage is 6.3 V or more.
Judgement Criterion
  • The monitor voltage is at a Low level during auto start (increasing voltage instruction).


  • The monitor voltage is at a High level for 2 seconds or more when not in auto start (without increasing voltage instruction).

FAIL-SAFE AND BACKUP FUNCTION



  • None.

PROBABLE CAUSES



  • Open/short circuit or harness damage in DC/DC converter (entertainment system) circuit or loose connector contact
  • Failed DC/DC converter (entertainment system)
  • Failed AS&G-ECU

DIAGNOSIS PROCEDURE


STEP 1. Perform voltage measurement at AS&G-ECU connector.



  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal DCCT and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 3.
Go to Step 2.

STEP 2. Check of short to earth and open circuit in DCCT line between DC/DC converter (entertainment system) connector and AS&G-ECU connector.


Q. Is the check result normal?

Replace the DC/DC converter (entertainment system).
Repair the connector(s) or wiring harness.

STEP 3. Perform voltage measurement at C-64 AS&G-ECU connector.



  • Measure the voltage AS&G-ECU connector terminal.
  • Ignition switch: ON
  • Voltage between terminal DCCT and earth.
OK: Voltage is 25% of the battery voltage or less.

Q. Is the check result normal?

Go to Step 5.
Go to Step 4.

STEP 4. M.U.T.-III diagnosis code



  • Reconfirmation of the diagnosis code.

Q. Is the diagnosis code set?

Replace the AS&G-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).

STEP 5. Perform voltage measurement at AS&G-ECU connector



  • Measure the voltage AS&G-ECU connector terminal.

  • Perform auto start with the following procedures.

  1. Change vehicle status to auto stop status.
  2. Selector lever: D range → P range
  3. Release the brake pedal then depress it again (Auto Start carried out at this point).

  • Voltage between terminal DCCP and earth.
OK: Voltage is 75% of the battery voltage or more.

Q. Is the check result normal?

Go to Step 7.
Go to Step 6.

STEP 6. M.U.T.-III diagnosis code



  • Reconfirmation of the diagnosis code.

Q. Is the diagnosis code set?

Replace the AS&G-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).

STEP 7. Check of harness damage in DCCT line between AS&G-ECU connector and DC/DC converter (entertainment system) connector


Q. Is the check result normal?

Go to Step 8.
Repair the connector(s) or wiring harness.

STEP 8. M.U.T.-III diagnosis code



  • Reconfirmation of the diagnosis code.

Q. Is the diagnosis code set?

Replace the AS&G-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).