System Operation Check

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

Trouble shooting of a steering column switch 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.
Inspect the multiplex communication system and confirm that there is no trouble by the basic inspection and DTC check. See PRE-CHECK under SELF-DIAGNOSTIC under MULTIPLEX COMMUNICATION SYSTEM article under COMMUNICATION DEVICES in ACCESSORIES & EQUIPMENT.

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⁾

Horns Blow 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

Ignition Switch Is Not Set To Each Position

⁽⁷⁾⁽⁸⁾

Key Unlock Warning Switch

Key Unlock Warning System Does Not Operate (Buzzer Does Not Sound When Driver's Door Is Opened With Ignition OFF & Key Inserted)

⁽⁹⁾⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾⁽¹³⁾⁽⁶⁾

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

⁽⁷⁾⁽¹⁴⁾⁽¹⁵⁾⁽⁶⁾

Turn Signal & Hazard Warning System

Hazard & Turn Do Not Light Up

⁽¹⁶⁾⁽¹⁷⁾⁽¹⁸⁾⁽⁶⁾

Flashing Frequency Is Abnormal

⁽¹⁹⁾⁽¹⁷⁾⁽⁶⁾

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

⁽²⁰⁾⁽⁶⁾

Hazard Warning Light Does Not Light Up In One Direction

⁽¹⁶⁾⁽⁶⁾

Turn Signal Does Not Light Up ⁽²¹⁾

⁽⁷⁾⁽¹⁵⁾⁽¹⁷⁾⁽⁶⁾

Turn Signal Does Not Light Up ⁽²²⁾

⁽¹⁵⁾⁽¹⁷⁾⁽⁶⁾

Turn Signal Does Not Light Up In One Direction

⁽¹⁷⁾⁽⁶⁾

Only One Bulb Does Not Light Up

⁽¹⁹⁾⁽⁶⁾

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

⁽²⁾	Check the HORN fuse in the engine room junction block.

⁽³⁾	Check the horn relay in the engine room junction block. See RELAYS under COMPONENT TESTS.

⁽⁴⁾	Check the horn switch. See HORN SWITCH under COMPONENT TESTS.

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

⁽⁶⁾	Check the wire harness.

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

⁽⁸⁾	Check the power source circuit.

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

⁽¹⁰⁾	Check the door courtesy switch. See AUTOMATIC HEADLIGHTS & LIGHTING article under HEADLIGHTS in ACCESSORIES & EQUIPMENT.

⁽¹¹⁾	Check the driver door ECU. See POWER DOOR LOCKS & LIFTGATE article under DOOR LOCKS & ANTI-THEFT SYSTEMS in ACCESSORIES & EQUIPMENT.

⁽¹²⁾	Check the multiplex communication circuit. See MULTIPLEX COMMUNICATION SYSTEM article under COMMUNICATION DEVICES in ACCESSORIES & EQUIPMENT.

⁽¹³⁾	Check the body ECU. See BODY CONTROL SYSTEM article under COMMUNICATION DEVICES in ACCESSORIES & EQUIPMENT.

⁽¹⁴⁾	Check the RADIO No. 2 fuse in the instrument panel junction block.

⁽¹⁵⁾	Check the GAUGE fuse in the instrument panel junction block.

⁽¹⁶⁾	Check the hazard warning switch. See HAZARD WARNING SWITCH under COMPONENT TESTS.

⁽¹⁷⁾	Check the turn signal switch. See TURN SIGNAL SWITCH under COMPONENT TESTS.

⁽¹⁸⁾	Check the turn signal flasher. See TURN SIGNAL FLASHER under COMPONENT TESTS.

⁽¹⁹⁾	Check the bulb.

⁽²⁰⁾	Check the HAZARD fuse in the engine room junction block.

⁽²¹⁾	The combination meter, wiper and washer do not operate.

⁽²²⁾	The combination meter, wiper and washer are normal.

Inspect the steering column switches circuits. See CIRCUIT TESTS .
After problem has been identified and repaired, confirm repairs. After repairs have been completed, confirm that problem has been eliminated. Operate system under same conditions recorded for original complaint. If problem is no longer present, repair has corrected problem. If problem is still present, further diagnosis and repair is required.