1998 Lexus LS 400FACTORY OEM SERVICE PROCEDURE

Remote Transmitter Functions Do Not Operate

  1. Ensure key is not inserted into ignition switch. All doors are closed and locked. Turn buzzer switch on (located on lower left side of instrument panel).
  2. Standing outside vehicle near driver's door, point transmitter toward vehicle. Press door lock and unlock switch on transmitter for about one second. If doors do not lock and unlock properly, go to next step. If doors lock and unlock properly, system is functioning properly at this time.
  3. Observe remote transmitter LED while pressing transmitter lock and unlock switch. If remote transmitter LED illuminates when transmitter lock and unlock switch is pressed, go to step  5. If remote transmitter LED does not illuminate when transmitter lock and unlock switch is pressed, go to next step.
  4. Replace remote transmitter battery. Check remote transmitter functions. If remote transmitter still does not operate properly, go to next step. If remote transmitter operates properly with new battery, old battery was faulty. System is now operating properly.
  5. Ensure key is not inserted into ignition switch. All doors are closed and locked. Turn buzzer switch on (located on lower left side of instrument panel).
  6. The following procedure must be carried out within 35 seconds. Insert key into ignition switch, then remove it, turn ignition on and off 10 times. Buzzer should sound a short tone followed by a longer tone, indicating successful entry to diagnostic mode. If buzzer sounds as specified, go to step  8. If buzzer does not sound and method used to enter diagnostic mode is correct, go to next step. If buzzer does not sound and method used to enter diagnostic mode is not correct, repeat procedure.
  7. If chirping function of confirmation buzzer is not normal in previous step, go to DOOR LOCK BUZZER DOES NOT CHIRP . If chirping function of confirmation buzzer is normal in previous step, check key unlock warning switch. See KEY UNLOCK WARNING SWITCH  under COMPONENT TESTS. If key unlock warning switch is okay, repair or replace circuits as necessary and retest system operation. See WIRING DIAGRAMS .
  8. Press LOCK button on remote transmitter. Buzzer should produce a short tone about every .5 second. Press UNLOCK button on transmitter. Buzzer should produce 2 short tones about every .5 second. Press trunk switch. Buzzer should produce a long tone about every .5 second. If buzzer does not operate for each button pressed, transmitter may be faulty. Try other transmitter. If buzzer operates as specified, go to step  10. If buzzer sounds a long continuous tone, go to next step.
  9. A long continuous tone indicates transmitter is operating, but transmitter code is not recognized by ECU. Perform VEHICLE ACCESS CODE PROGRAMMING  and recheck remote door lock operation. If remote door locks still do not operate properly, attempt diagnosis by symptom. See TROUBLE SHOOTING in BODY CONTROL SYSTEMS article.
  10. Standing at least 3 feet away from vehicle, press and hold transmitter switch. After holding button for 20 seconds, buzzer should stop. If operation is not as specified, check wireless door lock receiver ECU pin voltages. See PIN VOLTAGE TESTS . If operation is as specified, other problems exist in body control system. See BODY CONTROL SYSTEMS article.
  11. Repeat procedure in step  10 using other transmitter and check effective range. If buzzer operates as specified, replace original transmitter. If buzzer does not operate properly using both transmitters, go to next step.
  12. Using scan tool, check for DTC 42. If DTC 42 is not retrieved, go to next step. If DTC 42 is retrieved, check for faults in Brown/Red wire between wireless door lock receiver ECU and body control ECU. See WIRING DIAGRAMS . Repair or replace as necessary.
  13. Check circuits for opens between wireless door lock receiver ECU and body control ECU. If circuits are okay, go to next step. Repair or replace circuits as necessary.
  14. Check wireless door lock receiver ECU pin voltages. See PIN VOLTAGE TESTS . Replace original wireless door lock receiver ECU as necessary. Retest system operation. If system still does not operate properly, see TROUBLE SHOOTING SYMPTOMS table in BODY CONTROL SYSTEM article.
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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.