Code No. C2020:
Brake booster vacuum sensor power supply voltage abnormality (VP)
BRAKE BOOSTER VACUUM SENSOR CIRCUIT
OPERATION
The 5-V power is supplied from EV-ECU to the brake booster vacuum sensor, then the brake vacuum
is converted to the voltage and output to the EV-ECU.
DIAGNOSIS CODE SET CONDITIONS
- When the 5-V power supply voltage from the EV-ECU is
4.7 V max. or 5.3 V min., the diagnosis code No. C2020 will be set.
PROBABLE CAUSES
- Damaged wiring harness or connector(s)
- Malfunction of the brake booster vacuum sensor
- Malfunction of the EV-ECU
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STEP 1. Measure the voltage at A-105 brake booster vacuum
sensor connector.
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(1)Disconnect the A-105 brake booster vacuum sensor connector, and measure the voltage
at the wiring harness side.
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(2)Turn the electric motor switch to the "ON" position.
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(3)Measure the power supply voltage between the A-105 brake booster vacuum sensor
connector terminal No. 3 and the body earth.
OK: 4.7 to 5.3 V
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Q.
Is the check result normal?
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 Go to Step 4.
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 Go to Step 2.
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STEP 2. Connector check: C-106 EV-ECU connector, B-28 intermediate
connnector, A-105 brake booster vacuum sensor connector
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Q.
Is the check result normal?
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Go to Step 3.
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Repair the damaged connector.
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STEP 3. Check the wiring harness between A-105 brake booster vacuum
sensor connector terminal No. 2, 3 and C-106 EV-ECU connector terminal No. 7, 22.
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Check the power supply and earth lines for open circuit and short to earth.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the wiring harness.
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STEP 4. Diagnosis code recheck
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Check again if the diagnosis code is set to the EV-ECU.
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(1)Erase the stored diagnosis code.
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(2)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is the diagnosis code set?
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Replace the brake booster vacuum sensor. (Refer to GROUP 35A - Master
Cylinder Assembly and Brake Booster Assembly  <LHD>, <RHD>.)
Then go to Step 5.
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunction .)
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STEP 5. Diagnosis code recheck
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Check again if the diagnosis code is set to the EV-ECU.
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(1)Erase the stored diagnosis code.
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(2)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is the diagnosis code set?
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Replace the EV-ECU. (Refer to .) Then go
to Step 6.
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The diagnosis is complete.
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STEP 6. Diagnosis code recheck
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Check again if the diagnosis code is set to the EV-ECU.
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(1)Erase the stored diagnosis code.
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(2)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is the diagnosis code set?
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Return to Step 1.
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The diagnosis is complete.
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