Code No. P0622: Alternator FR Terminal System


OPERATION



  • The energized state of the alternator field coil is inputted from the alternator connector terminal to the engine-ECU connector terminal ALTF.

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 500 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.)

PROBABLE CAUSES



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

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at alternator connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: "ON"
  • Voltage between terminal engine-ECU ALTF line and body earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 4.
Go to Step 2.

STEP 2. Check harness between alternator connector terminal and engine-ECU connector terminal ALTF.

  • Check output line for open circuit.

Q. Is the check result normal?
Go to Step 3.
Repair or replace the connector, or repair the damaged harness wire.

STEP 3. 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 4. Check harness between alternator connector terminal and engine-ECU connector terminal ALTF.

  • Check output line for damage.

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

STEP 5. Perform voltage measurement at 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: P range
  • Radiator fan: Not operated
  • Voltage between terminal ALTF and body earth.
OK: Voltage decreases when the headlamps are extinguished → illuminated.

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