Trouble Shooting

WARNING: This page is about a different car, the 2003 Lexus IS 300 and 2002 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.

Trouble shooting of a multiplex communication system complaint begins with verification of the customer problem. If problem occurs, go to step 3. If problem does not occur, go to next step.
If problem does not occur, review conditions under which problem occurred for customer and try to duplicate those conditions. 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.
Perform pre-check. See PRE-CHECK under SELF-DIAGNOSTIC SYSTEM. If there is a normal code, go to the next step. If there is a malfunction code, go to step 5.
Determine problem symptom.
- Engine. See SELF-DIAGNOSTICS - IS300 article under FAULT ISOLATION in ENGINE PERFORMANCE.
- Body Control System. See BODY CONTROL SYSTEM article.
- Air Conditioning System. See AUTOMATIC A/C-HEATER SYSTEMS - IS 300 article in HVAC.
- Instrument Panel System. See INSTRUMENT PANEL article.
- Anti-Theft System. See ANTI-THEFT SYSTEM article.
Inspect multiplex communication circuits. See DIAGNOSTIC TESTS .
After problem has been identified and repaired, confirm repairs. See CONFIRMATION TEST under SELF-DIAGNOSTIC SYSTEM.