1990 Lexus ES 250 AutomaticFACTORY OEM SERVICE PROCEDURE

Theft Deterrent System Ignition Switch Circuit Test

  1. Turn ignition off. Check ECU-IG fuse. ECU-IG fuse is located in junction block No. 1 in driver kick panel area. If fuse is okay, repair short in wire harness between ECU-IG fuse and theft deterrent ECU terminal No. 2 of 18-pin connector. See Figure. If fuse is okay, go to next step.
  2. Disconnect theft deterrent ECU connectors. Theft deterrent ECU is located under dashboard, above glove box. Turn ignition switch to ACC or ON position. Using a DVOM, check for battery voltage on theft deterrent ECU terminal No. 2 of 18-pin connector. If battery voltage is not present, repair open circuit in wire harness between ECU-IG fuse and terminal No. 2 of 18-pin connector. If battery voltage is present, replace theft deterrent ECU and retest system. Theft deterrent ECU is located under dashboard, above glove box.
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

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.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.