Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSTOYOTA2004CELICA GT, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 249 (BODY ELECTRICAL SYSTEMS (TROUBLESHOOTING))TROUBLESHOOTINGPROBLEM SYMPTOMSTHEFT DETERRENT SYSTEM

2004 Toyota Celica GT, Standard

Theft Deterrent System

2004 Toyota Celica GT, StandardSECTION Theft Deterrent System

WARNING: This page is about a different car, the 2002 Toyota Sequoia. However, it is still accessible from the selected car via links, so may be relevant.

This system uses the multiplex communication system, so check diagnosis system of the multiplex communication system before you proceed with troubleshooting.

THEFT DETERRENT

Symptom/Suspect Area

See

System Cannot Be Set

Indicator Light

⁽¹⁾

Key Unlock Warning Switch

⁽²⁾

Door Unlock Detection Switch

⁽³⁾

Engine Hood Courtesy Switch

⁽⁴⁾

Back Door Courtesy Switch

⁽⁵⁾

Wire Harness

.....

Master SW (Driver Door ECU)

⁽⁶⁾

Passenger P/W SW (Passenger Door ECU)

⁽⁷⁾

Back Door ECU

⁽⁸⁾

Body ECU

⁽⁸⁾

System Cannot Be Canceled When Ignition Switch Is Turned On With Key

Key Unlock Warning Switch

⁽²⁾

Ignition Switch

⁽⁹⁾

ECU-IG Fuse

⁽¹⁰⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

System Cannot Be Canceled When Back Door Is Unlocked With Key

Back Door ECU

⁽¹¹⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

System Does Not Operate When Engine Hood Is Opened

Engine Hood Courtesy Switch

⁽⁴⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

System Does Not Operate When Ignition Switch Is Turned To ACC Without Using Key Or Transmitter

Ignition Switch

⁽⁹⁾

Key Unlock Warning Switch

⁽²⁾

Transmitter

⁽¹²⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

Some Of The System Does Not Operate (Headlight Does Not Light Up)

Headlight System

⁽¹³⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

Some Of The System Does Not Operate (Taillight Does Not Light Up)

Taillight System

⁽¹⁴⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

Some Of The System Does Not Operate (Theft Deterrent Horn Or Horn Does Not Sound)

Horn Fuse

⁽¹⁰⁾

Theft Deterrent Horn

⁽¹⁵⁾

Horn

⁽¹⁶⁾

Horn Relay

⁽¹⁷⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

While Warning Is Given, System Cannot Be Canceled By Unlocking Door With Key Or Transmitter

Door Key Lock And Unlock Switch

⁽¹⁸⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

While Warning Is Given, System Cannot Be Canceled By Turning Ignition Switch To ACC Or ON With Key

Ignition Switch

⁽⁹⁾

Key Unlock Warning Switch

⁽²⁾

RAD No. 2 Fuse

⁽¹⁰⁾

ECU-IG Fuse

⁽¹⁰⁾

Wire Harness

.....

Body ECU

⁽⁸⁾

System Operates For More Than 60 Seconds

Body ECU

⁽⁸⁾

⁽¹⁾

⁽²⁾	INSPECT KEY UNLOCK WARNING SWITCH CONTINUITY

⁽³⁾	See Steps 3-5 Of INSPECTION

⁽⁴⁾	See Step 2 Of INSPECTION

⁽⁵⁾	See Step 8 Of INSPECTION

⁽⁶⁾	DRIVER DOOR CONTROL SYSTEM - DIAGNOSTICS

⁽⁷⁾	PASSENGER DOOR CONTROL SYSTEM - DIAGNOSTICS

⁽⁸⁾	BODY, CAB CONTROL SYSTEMS

⁽⁹⁾	INSPECT IGNITION SWITCH CONTINUITY

⁽¹⁰⁾	FUSES & CIRCUIT BREAKERS

⁽¹¹⁾	BACK DOOR CONTROL SYSTEMS - DIAGNOSTICS

⁽¹²⁾	INSPECT WIRELESS DOOR LOCK TRANSMITTER OPERATION

⁽¹³⁾	HEADLIGHTS

⁽¹⁴⁾	HEADLIGHT AND TAILLIGHT SYSTEM

⁽¹⁵⁾	INSPECTION

⁽¹⁶⁾	HORN SYSTEM

⁽¹⁷⁾	INSPECTION

⁽¹⁸⁾	INSPECTION

RENDER: 1.0x

NO RELATED

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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.