P0622 – Alternator FR Terminal System MMC Colt



OPERATION

  • The energized state of the alternator field coil is inputted from the alternator (terminal No. 4) to the engine-ECU (terminal No. 54).

  • 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

  • Engine speed is 50 r/min or higher.
  • Input voltage from the alternator FR terminal has continued to be approximately battery positive voltage for 20 seconds.

  • PROBABLE CAUSES

  • Failed alternator
  • Open or shorted alternator FR terminal circuit, harness damage, or connector damage
  • Failed engine-ECU

  • DIAGNOSIS PROCEDURE

    STEP 1. Connector check: A-127 alternator connector

    Q. Is the check result normal?

    STEP 2. Perform voltage measurement at A-127 alternator connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 4 and earth.
  • Q. Is the check result normal?

    STEP 3. Connector check: A-08 engine-ECU connector.

    Q. Is the check result normal?

    STEP 4. Check harness between A-127 (terminal No. 4) alternator connector and A-08 (terminal No. 54) engine-ECU connector.

  • Check output line for open/short circuit.
  • Q. Is the check result normal?

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

  • Reconfirmation of diagnosis code.
  • Q. Is the diagnosis code set?

    STEP 6. Perform voltage measurement at A-08 engine-ECU connector.

  • Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB991987), and then measure the voltage on the check connector.
  • Engine: Idle after warm-up
  • Transmission: Neutral
  • Radiator fan: Inactive
  • Voltage between terminal No. 54 and earth.
  • Q. Is the check result normal?

    STEP 7. Check harness between A-127 (terminal No. 4) alternator connector and A-08 (terminal No. 54) engine-ECU connector.

  • Check output line for damage.
  • Q. Is the check result normal?

    STEP 8. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.
  • Q. Is the diagnosis code set?

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