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Theft Deterrent Ecu

  1. Turn ignition off. Disconnect theft deterrent ECU connectors. Theft deterrent ECU is located under dashboard, left of steering column. Turn ignition switch to START position. Place transmission in Neutral. Using a DVOM, check for battery voltage between terminal No. 1 of 18-pin connector and ground. See Fig 1.
    Fig 1: Identifying LS400 Theft Deterrent ECU Harness Connector Terminals
    G90E18873Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. If battery voltage is not present, repair harness and connector between starter relay and theft deterrent ECU. If battery voltage is present, go to next step.
  3. Turn ignition off. Connect theft deterrent ECU connectors. Using a DVOM, measure resistance between theft deterrent ECU connector terminal No. 14 of 18-pin connector and ground. See Fig 1. Resistance should be one ohm or less.
  4. If resistance is within specification, replace ECU with a known good unit and retest system. If resistance is not within specification, disconnect theft deterrent ECU connector.
  5. Check theft deterrent ECU ground terminal and wire harness connector for damage. Repair as necessary. If theft deterrent ECU ground terminal and wire harness connector are okay, replace theft deterrent ECU and retest system.