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.
2003 Lexus IS 300 Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Multiplex Communication System DTCS
MULTIPLEX COMMUNICATION SYSTEM DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION
| DTC | Description |
|---|---|
| B1211/11 | Power Window Master Switch ECU Communication Stop |
| B1214/14 | Communication Bus Malfunction (+B Short) |
| B1215/15 | Communication Bus Malfunction (GND Short) |
| B1241/41 | Body ECU Switch Circuit Diagnosis |
| B1242/42 | Wireless Door Lock Tuner Circuit Malfunction |
| B1244/44 | Light Sensor Circuit Malfunction |
| B1261/61 | ECM Communication Stop |
| B1262/62 | A/C ECU Communication Stop |
| B1269/69 | Anti-Theft ECU Communication Stop |
| B1271 | Combination Meter ECU Communication Stop |
Factory Service Tools
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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.
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