Code No. P0620: Alternator Control Circuit <Euro5b>


OPERATION



  • When the ignition switch is turned ON, the current should be supplied from the combination meter (terminal No. 52) to the alternator (terminal No. 3). When the engine starts under those conditions, the alternator should generate currents.
  • The engine-ECU checks the voltage of the battery backup terminal (terminal No. 103) to monitor the electricity generation voltage of the alternator.

FUNCTION



  • The engine-ECU compares the battery voltage with the voltage generated from the alternator to check whether the electrical generation is normal.

TROUBLE JUDGMENT


Check Conditions
  • Ignition switch is "ON" position.
  • The engine speed is 1 500 r/min or more.
  • The battery backup voltage is 13.5 V or more.
  • The G-terminal duty ratio is 10.2 % or more and 89.8 % or less.
Judgement Criterion
  • For 30 seconds, the final target generation voltage subtracted from the battery backup voltage equals 0.8 V or more.


  • For 30 seconds, the battery backup voltage subtracted from the final target generation voltage equals 1.9 V or more.

PROBABLE CAUSES



  • Failed battery
  • Failed drive belt
  • Loose connector contact
  • Open/short circuit or harness damage in alternator G-terminal circuit
  • Harness damage in battery backup circuit
  • Failed alternator
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Checking engine start conditions

  • Check whether the user uses the booster cable to start the engine.
note This diagnosis code can be output due to the battery voltage drop.

Q. Have you ever used the booster cable to start the engine?
Delete the diagnosis code and check end.
Go to Step 2.

STEP 2. Battery check

  • Check the battery (Refer to GROUP 54A - Battery - On-vehicle Service - Battery Test ).

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

STEP 3. Drive belt tension check

  • Drive belt tension check (Refer to GROUP 11A - On-vehicle Service - Alternator and Power Steering Oil Pump Drive Belt Tension Check ).

Q. Is the check result normal?
Go to Step 4.
Replace the drive belt.

STEP 4. Connector check: C-103 engine-ECU connector

Q. Is the check result normal?

Go to Step 5.

Repair or replace the connector.

STEP 5. Perform voltage measurement at C-103 engine-ECU connector.


  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 121 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 8.

Go to Step 6.

STEP 6. Connector check: A-122 alternator connector

Q. Is the check result normal?

Go to Step 7.

Repair or replace the connector.

STEP 7. Check harness between C-103 (terminal No. 121) engine-ECU connector and A-122 (terminal No. 1) alternator connector.


note Before checking harness, check intermediate connectors A-27 and A-115, and repair if necessary.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?

Check the alternator.

Repair the damaged harness wire.

STEP 8. Check harness between battery and C-103 (terminal No. 103) engine-ECU connector.

note Before checking harness, check intermediate connector A-115, and repair if necessary.

  • Check power supply line for damage.

Q. Is the check result normal?

Go to Step 9.

Repair the damaged harness wire.

STEP 9. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.

Q. Is diagnosis code set?
Go to Step 10.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 10. Replace the drive belt

  • After replacing the drive belt, reconfirm whether the diagnosis code is set.

Q. Is diagnosis code set?
Go to Step 11.
Check end.

STEP 11. Replace the alternator

  • After replacing the alternator, reconfirm whether the diagnosis code is set.

Q. Is diagnosis code set?
Replace the engine-ECU. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - Precautions Before Service - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ). After registering the injector identification code, carry out the forcible DPF regeneration. (Refer to GROUP 17 - Emission Control - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).
Check end.