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LS400 Theft Deterrent Ecu Operation Test

  1. If no malfunction is found in circuit tests, check theft deterrent ECU operation and ground circuit. Theft deterrent ECU is located under left side of dash, above junction block No. 1.
  2. Connect theft deterrent ECU connectors. Close all vehicle doors. Turn ignition switch to ON position. Use DVOM at rear of ECU connector. Check for battery voltage between theft deterrent ECU harness connector terminal B8 and ground. See Figure.
  3. Turn ignition switch to OFF position. Battery voltage should be present between harness connector terminal B8 and ground for approximately 60 seconds after ignition switch has been turned off. Cycle ignition switch on and off. Battery voltage should remain at terminal B8 for at least 60 seconds.
  4. Turn ignition switch to OFF position. Open front door within 60 seconds of turning ignition switch off. Battery voltage should not be present between harness connector terminal B8 and ground.
  5. Close all doors, and turn ignition switch to ON position. Open front door. Battery voltage should be present between harness connector terminal B8 and ground. Turn ignition switch to OFF position. Voltage should not exist between ECU harness terminal B8 and ground. Check ground circuit, and replace ECU as necessary.
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