Code No. P0622: Alternator FR Terminal System


OPERATION



  • The energized state of the alternator field coil is inputted from the alternator (terminal No. 4) to the engine-ECU (terminal No. 61).

FUNCTION



  • A signal of the power supply duty ratio for the alternator field coil is inputted to the engine-ECU.
  • In response to the signal, the engine-ECU detects the alternator output current and controls the idling speed according to the output current (electric load).

TROUBLE JUDGMENT


Check Condition
  • Engine speed is more than 50 r/min.
Judgement Criterion
  • Input voltage from the alternator FR terminal is approximately battery positive voltage for 20 seconds.

FAIL-SAFE AND BACKUP FUNCTION



  • Prohibits alternator output suppression control against current consumers. (operate as a normal alternator.)
  • The auto stop is prohibited. <Vehicles with AS&G system>

PROBABLE CAUSES



  • Failed alternator
  • Open circuit or harness damage in alternator circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-117 alternator connector

Q. Is the check result normal?
Go to Step 2 .
Repair or replace the connector.

STEP 2. Perform voltage measurement at B-117 alternator connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 4 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 6 .
Go to Step 3 .

STEP 3. Connector check: B-26 engine-ECU connector

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

STEP 4. Check harness between B-117 (terminal No. 4) alternator connector and B-26 (terminal No. 61) engine-ECU connector.

  • Check output line for open circuit.

Q. Is the check result normal?
Go to Step 5 .
Repair the damaged harness wire.

STEP 5. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.

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

STEP 6. Connector check: B-26 engine-ECU connector

Q. Is the check result normal?
Go to Step 7 .
Repair or replace the connector.

STEP 7. Check harness between B-117 (terminal No. 4) alternator connector and B-26 (terminal No. 61) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 8 .
Repair the damaged harness wire.

STEP 8. Perform voltage measurement at B-26 engine-ECU connector.

  • Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB992110) to measure at connector for inspection.
  • Engine: Idle operation after warm-up
  • Transmission: Neutral
  • Radiator fan: Not operated
  • Voltage between terminal No. 61 and earth.
OK: Voltage decreases when the headlamps are extinguished → illuminated.

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