2021 Mazda 3 BaseFACTORY OEM SERVICE PROCEDURE

LF Control Unit Removal/Installation

CAUTION:
  • When replacing the LF control unit, perform the configuration to assure that the system operates correctly.
  1. To replace the LF control unit, perform the following procedure.
    1. Connect the M-MDS to the DLC-2.
    2. Switch the ignition ON (engine off).
    3. Activate the M-MDS and perform the following procedure.
      1. Press [Start] to start the vehicle identification.
      2. Press the [Toolbox] tab.
      3. Press the [Work Support] icon.
      4. Press [Configuration].
      5. Press [Run] to perform the configuration.
      6. Press [LFU].
      7. When [Install the new ECU] is displayed, move to the LF control unit replacement procedure.
  2. Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .)
  3. Remove the front scuff plate (RH). (See FRONT SCUFF PLATE REMOVAL/INSTALLATION .)
  4. Remove the front side trim (RH). (See FRONT SIDE TRIM REMOVAL/INSTALLATION .)
  5. Disconnect the connector.
    G13179093Courtesy of MAZDA MOTORS CORP.
  6. While pressing the bracket tabs in the directions of arrows (1) shown in the figure, pull out the LF control unit from the backside of the bracket in the direction of arrow (2) and detach the bracket tabs from the LF control unit.
    G13179094Courtesy of MAZDA MOTORS CORP.
  7. Remove the LF control unit.
  8. Install in the reverse order of removal.
  9. If the LF control unit is replaced, perform the following procedure.
    1. Return to the M-MDS operation and press [Continue].
    2. When the M-MDS processing is completed, press [Next].
    3. When the M-MDS processing is completed, press [Next].
    4. Verify that the following conditions/operations are met/completed, mark the check boxes, and then press [Next].
      • Switch the ignition ON (engine off)
      • Install battery charger to vehicle
      • Lead-acid Battery voltage:11.6 V or more
      • Connect power cable to M-MDS
      • Front doors on both sides and liftgate are open
    5. Press [Finish].
    6. Switch the ignition OFF.
    7. Switch the ignition ON (engine off) to complete the global central configuration (GCC) for the LF control unit.
    8. Perform the immobilizer system-related part programming using the M-MDS. (See IMMOBILIZER SYSTEM-RELATED PARTS PROGRAMMING (US) .)
    9. Clear the DTC. (See CLEARING DTC .)
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.