Code No.B120A Security alarm siren error
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- Before replacing the ECU or sensor, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
- When the ETACS-ECU of vehicles without KOS is replaced, the encrypted code of the ignition key needs to be registered to the ETACS-ECU. (If the encrypted code is not registered, the engine cannot be started. Register the encrypted code as described in Immobilizer System - How to Register Key ID
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DIAGNOSTIC FUNCTION
- The security alarm siren communicates with the ETACS-ECU by the LIN. The diagnosis code No. B120A is stored if the communication data between the ETACS-ECU and security alarm siren has an error.
PROBABLE CAUSES
Malfunction of security alarm siren
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STEP 1. M.U.T.-III diagnosis code.
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Check if diagnosis code is stored in the ETACS-ECU.
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Q.
Is the diagnosis code stored?
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 Diagnose the ETACS-ECU. Refer to GROUP 54A, Diagnosis .
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 Go to Step 2.
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STEP 2. Security alarm siren operation check
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(1)Set the security alarm to the "Ready to be triggered" condition.
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(2)Open the driver’s door by using the ignition key.
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(3)Check that the security alarm siren sounds.
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Q.
Is the check result normal?
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The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
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Go to Step 3.
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STEP 3. Replace the security alarm siren temporarily, and check whether the diagnosis code is stored.
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Check again if the diagnosis code is stored in the ETACS-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.
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(3)Check if diagnosis code is stored.
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Q.
Is the diagnosis code stored?
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Replace the ETACS-ECU.
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Replace the security alarm siren.
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