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.
Multiplex Communication System Diagnostic Trouble Code Chart
If a malfunction code is displayed during the DTC check, check the circuit listed for that code in DTC CHART . Proceed to the procedure for that circuit.
DTC 21, 22, and 41 don't mean switch abnormal but notify how switch works.
If DTC is not output when operating switch, it means failure of switch contact.
If DTC is output when not opening switch, it means stick of switch.
| DTC | Trouble Area |
| B1211/11 | Wire harness, Driver Door ECU |
| B1221/21 | Power Window Master Switch, Wire harness |
| B1222/22 | Door Lock Control Switch, Door Key Lock & Unlock Switch, Wire Harness |
| B1241/41 | Stop Light Switch, Wire Harness |
| B1242/42 | Wire Harness, Wireless Door Lock Tuner |
| B1248/48 | Wire Harness, Gateway ECU |
| B1261/61 | Wire Harness, ECM |
| B1262/62 | Wire Harness, A/C amplifier |
| B1266/66 | Wire Harness, ECU (Instrument Panel System) |
| B1267/67 | Wire Harness, ECU (Instrument Panel System) |
| B1271/71 | Wire Harness, Combination Meter ECU |
| B1274/74 | Wire Harness, Multi Display |
| B1293/93 | Wire Harness, Power Source Circuit, Gateway ECU |
| POWER SOURCE CIRCUIT | Wire Harness, Power Source Circuit, Gateway ECU |
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.