2003 Lexus LS 430FACTORY OEM SERVICE PROCEDURE

Trouble Shooting

WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
  1. Trouble shooting of a multiplex communication system complaint begins with verification of the customer problem. Perform Customer Problem Analysis (Multiplex Communication System Check List). See Fig 1. If problem occurs, go to step  3. If problem does not occur, go to next step.
  2. If problem does not occur, review conditions under which problem occurred for customer. For example, if the problem occurs on rainy days or during high humidity conditions, sprinkle water onto vehicle and see if malfunction occurs. DO NOT sprinkle water directly into engine compartment or onto electronic components. Visually inspect for signs of mechanical and electrical damage. Inspect for blown fuses and damaged relays. Inspect for loose or corroded connections, damaged wiring harnesses and/or switches. Check for a broken or partially broken wire inside insulation, which could cause system malfunction but prove good in a continuity/voltage check with system disconnected. Ensure any aftermarket electronic equipment is properly installed. If fault is found, repair as necessary. If problem still cannot be created, go to next step.
  3. Perform basic inspection. See BASIC INSPECTION  under SELF-DIAGNOSTIC SYSTEM. If basic inspection confirms diagnostic system is functional, retrieve Diagnostic Trouble Codes (DTCs). See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM.
  4. After problem has been identified and repaired, confirm repairs. See CONFIRMATION TEST  under SELF-DIAGNOSTIC SYSTEM.
Fig 1: Customer Problem Analysis (Multiplex Communication System Check List)
G00124325Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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.