System Operation Check

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 steering column switches complaint begins with verification of 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 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.
Inspect multiplex communication system and confirm that there is no trouble by basic inspection and DTC check. See PRE-CHECK under SELF-DIAGNOSTIC SYSTEM in MULTIPLEX COMMUNICATION SYSTEM article in COMMUNICATION DEVICES.

Determine problem symptom. See PROBLEM SYMPTOM INDEX table.

PROBLEM SYMPTOM INDEX

Symptom

Suspected Area ⁽¹⁾

Horn System

Horn System Does Not Operate

⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾⁽⁶⁾

Horn Blows All The Time

⁽³⁾⁽⁴⁾⁽⁶⁾

One Horn Operates But Other Horn Does Not Operate

⁽⁵⁾⁽⁶⁾

Horns Operate Abnormally

⁽³⁾⁽⁵⁾⁽⁶⁾

Ignition Switch & Key Unlock Warning Switch

Ignition Switch Is Not Set To Each Position

⁽⁷⁾⁽⁸⁾

Key Unlock Warning System Does Not Operate (Buzzer Sounds When Ignition Key Is ACC Or ON)

⁽⁷⁾⁽⁹⁾⁽¹⁰⁾⁽¹¹⁾⁽⁶⁾

Turn Signal & Hazard Warning System

Hazard & Turn Do Not Light Up

⁽¹²⁾⁽⁷⁾⁽¹³⁾⁽⁶⁾

Hazard Warning Light Does Not Light Up (Turn Is Normal)

⁽¹⁴⁾⁽⁶⁾

Turn Signal Does Not Light Up (Hazard Is Normal)

⁽¹⁵⁾⁽⁶⁾

Turn Signal Does Not Light Up In One Direction

⁽¹⁵⁾⁽⁶⁾

Only One Bulb Does Not Light Up

⁽¹⁶⁾⁽⁶⁾

⁽¹⁾	Perform test procedures in order listed under suspected area.

⁽²⁾	Check HORN fuse located in engine room No. 1 relay block.

⁽³⁾	Check horn relay. See RELAYS under COMPONENT TESTS and HORN SWITCH & RELAY CIRCUIT under CIRCUIT TESTS.

⁽⁴⁾	Check horn switch. See HORN SWITCH under COMPONENT TESTS and HORN SWITCH & RELAY CIRCUIT under CIRCUIT TESTS.

⁽⁵⁾	Check horn. See HORN under COMPONENT TESTS.

⁽⁶⁾	Check wiring harness.

⁽⁷⁾	Check ignition switch. See IGNITION SWITCH under COMPONENT TESTS and IGNITION SWITCH CIRCUIT under CIRCUIT TESTS.

⁽⁸⁾	Check power source circuit.

⁽⁹⁾	Check key unlock warning switch. See KEY UNLOCK WARNING SWITCH under COMPONENT TESTS and KEY UNLOCK WARNING SWITCH CIRCUIT under CIRCUIT TESTS.

⁽¹⁰⁾	Check body ECU. See BODY CONTROL SYSTEM article in COMMUNICATION DEVICES.

⁽¹¹⁾	Check combination meter. See INSTRUMENT PANEL article.

⁽¹²⁾	Check GAUGE fuse located in driver side junction block then TURN HAZ fuse located in engine room No. 1 relay block.

⁽¹³⁾	Check turn signal flasher relay located in driver side junction block.

⁽¹⁴⁾	Check A/C control panel. See AUTOMATIC A/C-HEATER SYSTEMS - IS 300 article in HVAC.

⁽¹⁵⁾	Check turn signal switch. See TURN SIGNAL SWITCH under COMPONENT TESTS and TURN SIGNAL SWITCH CIRCUIT under CIRCUIT TESTS.

⁽¹⁶⁾	Check bulb.