INSPECTION PROCEDURE 4: HBB buzzer does not stop sounding.
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This diagnosis procedure is limited to cases where
communication with the M.U.T.-III is possible (ASTC-ECU power supply is
normal) and no diagnosis code sets.
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OPERATION
- The ASTC-ECU and the transfer-ECU controls the buzzer by turning the
power transistor in the ECU ON and OFF.
- The ASTC-ECU outputs the buzzer-sounding signal when an abnormality
occurs on the hydraulic brake booster (At the same time, the ASTC-ECU turns
on the brake warning light).
COMMENT ON TROUBLE SYMPTOM
The cause is probably an ASTC-ECU
malfunction.
PROBABLE CAUSES
- Damaged wiring harness or connector
- Malfunction of the ASTC-ECU
- Malfunction of the buzzer
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STEP 1. Check the buzzer circuit at ASTC-ECU connector
D-232.
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Disconnect ASTC-ECU connector D-232.
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Q.
Does the buzzer still keep on sounding?
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 Go to Step 2.
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 Replace the ASTC-ECU (Refer to
GROUP 35C, ASTC-ECU  ). Then go to Step 5.
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STEP 2. Check buzzer connector D-102, ASTC-ECU connector D-232 and
transfer-ECU connector D-123 for loose, corroded or damaged terminals, or
terminals pushed back in the connector.
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Q.
Are the connectors and terminals in good condition?
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Go to Step 3.
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Repair the faulty connector or
terminal. Then go to Step 5.
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STEP 3. Check intermediate connector D-225 for loose, corroded or
damaged terminals, or terminals pushed back in the
connector.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair or replace it. Then go to
Step 5.
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STEP 4. Check the following harness wires.
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- The wire between buzzer connector D-102 (terminal 2) and ASTC-ECU
connector D-232 (terminal 54)
- The wire between buzzer connector D-102 (terminal 2) and transfer-ECU
connector D-123 (terminal 51)
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Q.
Is the check result normal?
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Replace the buzzer (Refer to ). Then go to Step 5
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Repair or replace it. Then go to
Step 5.
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STEP 5. Retest the system.
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Before connecting or disconnecting the M.U.T.-III,
turn the ignition switch to the "LOCK" (OFF) position.
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(1)Connect M.U.T.-III to the diagnosis connector.
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(2)Turn the ignition switch to the "ON" position.
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(3)Using M.U.T.-III, check actuator test and sound the
buzzer.
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Q.
Does the buzzer sound for three seconds and then stop?
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The
procedure is complete.
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Start over at Step 1.
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