Code No. B1353: DC/DC Converter (Control System) Control Circuit


OPERATION



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

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.
  • Not in auto stop.
Judgement Criterion
  • Low monitor voltage of the increasing voltage instruction signal is detected after the engine is manually started.


  • 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



  • In the normal operation, the auto stop is prohibited.
  • If the malfunction is detected during the auto stop, the auto start is prohibited.

PROBABLE CAUSES



  • Open/short circuit or harness damage in DC/DC converter (control system) circuit or loose connector contact
  • Failed DC/DC converter (control 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 DCCP 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 DCCP line between DC/DC converter (control system) connector and AS&G-ECU connector.



  • Check output line for open/short circuit.

Q. Is the check result normal?
Replace the DC/DC converter (control system).
Repair the connector(s) or wiring harness.

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

  • Measure the voltage AS&G-ECU connector terminal.
  • Ignition switch: ON
  • Voltage between terminal DCCP 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. Check of harness damage in DCCP line between DC/DC converter (control system) connector and AS&G-ECU connector



  • Check output line for damage.

Q. Is the check result normal?
Go to Step 6.
Repair the connector(s) or wiring harness.

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).