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 324 (MULTIPLEX COMMUNICATION SYSTEM - DIAGNOSTICS)
2004 Toyota Celica GT, Standard
Section 324 (Multiplex Communication System - Diagnostics)
2004 Toyota Celica GT, StandardSECTION Section 324 (Multiplex Communication System - Diagnostics)
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.
- Service Precautions
- How To Proceed With Troubleshooting Multiplex Communication System
- Customer Problem Analysis Check
- Multiplex Communication System Pre-Check
- Multiplex Communication System Diagnostic Trouble Code Chart
- Multiplex Communication System Parts Location
- Terminals Of Ecu
- Circuit Inspection
- DTC B1211/11: Driver Door Ecu Communication Stop
- DTC B1221/21: Power Window Switch Circuit On Driver Door, DTC B1222/22: Door Lock Switch Circuit On Driver Door, DTC B1241/41: Body Ecu Switch Circuit Diagnosis
- DTC B1242/42: Wireless Door Lock Tuner Circuit Malfunction
- DTC B1248/48: AVC-LAN Circuit Communication Stop
- DTC B1261/61: ECM Communication Stop
- DTC B1262/62: A/C Amplifier Communication Stop
- DTC B1266/66: Instrument Panel System Communication Bus Malfunction (+B Short), DTC B1267/67: Instrument Panel System Communication Bus Malfunction (GND Short)
- DTC B1271/71: Combination Meter Ecu Communication Stop
- DTC B1274/74: Multi Display Communication Stop
- DTC B1293/93: Gateway Ecu Communication Stop
- Power Source Circuit
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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.