1992 Lexus LS 400FACTORY OEM SERVICE PROCEDURE

Ecu Power Source Circuit Test

  1. When remote door lock main switch is on, battery voltage is applied to terminal No. 2 of remote door lock ECU, causing ECU to operate. See Figure. If ECU does not operate, check DOME fuse and replace as necessary. Gain access to remote door lock ECU. Using a DVOM, measure voltage between ECU terminals No. 2 and 9.
  2. With remote door lock main switch in ON position, 10-14 volts should be present. With remote door lock main switch in OFF position, voltage should not be present. If voltage is as specified, circuit is okay. If voltage is not as specified, check and repair ground circuit as necessary.
  3. If ground circuit is okay, remove instrument panel lower finish panel and remove remote door lock main switch. Disconnect switch connector. Using an ohmmeter, check continuity between switch terminals. With remote door lock main switch in ON position, continuity should exist. With remote door lock main switch in OFF position, continuity should be one megohm or more.
  4. If switch does not test as described, replace main switch. If switch tests as described, check and repair wiring circuit(s) between ECU and main switch, and main switch and battery as necessary.
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.