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.

SYS.OK|MANUAL.DB● LIVE

HOMESERVICE MANUALSTOYOTA2004CELICA GT, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 324 (MULTIPLEX COMMUNICATION SYSTEM - DIAGNOSTICS)CIRCUIT INSPECTIONPOWER SOURCE CIRCUITINSPECTION PROCEDURE

2004 Toyota Celica GT, Standard

Inspection Procedure

2004 Toyota Celica GT, StandardSECTION Inspection Procedure

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

Check ECU-B and ECU-IG fuse.
CHECK: continuity of ECU-B and ECU-IG fuse.

OK: Continuity.
1. NG: Replace the failure fuse.
2. OK: Go to 2 .
Check voltage between terminals BATT, IG and GND of body ECU connector.
PREPARATION
1. Turn ignition switch OFF.
2. Disconnect the gateway ECU connector.
CHECK: Measure voltage between terminals BATT and GND.

OK: Voltage: 10 - 14 V.
1. OK: Check and repair wire harness and connector between gateway ECU and battery.
2. NG: Go to 3.
Check wire harness and connector between gateway ECU and body ground . See HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE .
1. NG: Repair or replace wire harness or connector.
2. OK: Check and repair wire harness and connector between gateway ECU and battery.

RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready Tools Free Quote Check Quote 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.