Code No. B1356: DC/DC Converter (Control System) Diag Output Line


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 the DC/DC converter’s (control system) diagnostic signal circuit whether it is normal.

TROUBLE JUDGMENT


Check Condition
  • For 10 seconds after the ignition is switched "OFF".
Judgement Criterion
  • The Low signal (ON signal) is received in a row.

FAIL-SAFE AND BACKUP FUNCTION



  • In the normal operation, the auto stop is prohibited.

PROBABLE CAUSES



  • Short circuit 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 DC/DC converter (control system) connector.

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

Q. Is the check result normal?
Go to Step 2.
Repair the connector(s), or check and repair of short to earth circuit in DCDP line between DC/DC converter (control system) connector and AS&G-ECU connector.

STEP 2. M.U.T.-III data list



  • Ignition switch: ON
  • Disconnect DC/DC converter (control system) connector.
  • Item 27: DC-DC OUT for powertrain (Input)
OK: OFF

Q. Is the check result normal?
Go to Step 4.
Go to Step 3.

STEP 3. 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 4. M.U.T.-III diagnosis code

  • Reconfirmation of the diagnosis code.

Q. Is the diagnosis code set?
Replace the DC/DC converter (control system).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).