INSPECTION PROCEDURE 1: When the hydraulic brake booster (HBB) abnormality
occurs, the HBB buzzer does not sound. (The brake warning lamp
illuminates.)
OPERATION
- The ABS-ECU controls the buzzer by turning the power transistor in the
ABS-ECU ON and OFF.
- The ABS-ECU outputs the buzzer-sounding signal at the malfunction of the
hydraulic brake booster (HBB). (Also the ABS-ECU turns on the brake warning
light at the same time.)
- The buzzer will sound under the following cases:
- When the pump motor is locked (Diagnosis code No.55 is
set).
- When the pump motor is operated for a long time continuously
(Diagnosis code No.78 is set.)
COMMENT ON TROUBLE SYMPTOM
It is suspected that the HBB buzzer
circuit is open, the HBB buzzer malfunction or the ABS-ECU internal buzzer
drive transistor malfunction occurs, or the circuit between the ignition
switch and ABS-ECU through HBB buzzer is open.
Probable causes
- Damaged wiring harness or connector
- Malfunction of the buzzer
- Malfunction of the ABS-ECU
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STEP 1. Check buzzer connector D-102 and ABS-ECU connector D-250 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 2.
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 Repair the faulty connector or
terminal. Then go to Step 8.
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STEP 2. Check the buzzer circuit at ABS-ECU harness connector
D-250.
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(1)Disconnect ABS-ECU connector D-250 and check at the
harness connector (component side).
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(2)Turn the ignition switch to the "ON" position.
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(3)Connect terminal 44 to body earth.
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Q.
Does the buzzer sound?
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Replace the ABS-ECU (Refer to
GROUP 35B, ABS Control Unit  ). Then go to Step 8.
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Go to Step 3.
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STEP 3. Check the buzzer.
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(1)Remove the buzzer (Refer to ).
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(2)Connect the battery to the buzzer as shown
on the illustration.
Q.
Does the buzzer sound?
Go to Step 4.
Replace the buzzer
(Refer to ). Then go to Step 8
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STEP 4. Check the buzzer power supply circuit at buzzer harness
connector D-102.
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(1)Disconnect buzzer connector D-102, and measure at the
harness connector (component side).
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(2)Turn the ignition switch to the "ON" position.
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(3)Measure the voltage between terminal 1 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 5.
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Go to Step 6.
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STEP 5. Check the harness wires between buzzer connector D-102
(terminal 2) and ABS-ECU connector D-250 (terminal 44).
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Q.
Is the check result normal?
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Go to Step 8.
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Repair or replace it. Then go to
Step 8.
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STEP 6. Check joint connector (6) D-113 <4M4>, joint
connector (5) D-111 <6G7>, intermediate connector D-230, joint
connector (4) D-34, junction block connector D-405 and junction block
connector D-403 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 7.
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Repair it. Then go to Step
8.
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STEP 7. Check the harness wires between buzzer connector D-102
(terminal 1) and junction block connector D-403 (terminal
2).
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Q.
Is the check result normal?
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Go to Step 8.
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Repair it. Then go to Step
8.
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STEP 8. Retest the system.
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(1)Apply a chock to the wheel.
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(3)When 120 seconds or more have been elapsed since the
engine was started, release the parking brake lever and fully depress the
brake pedal repeatedly 15 to 20 times within 10 seconds.
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Q.
Does the buzzer sound?
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The
procedure is complete.
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Start over at Step 1.
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