Code No. P0A78:
IGBT continuation abnormality (MCU)
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If there is any problem in the CAN bus lines,
an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose the CAN bus lines.
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ELECTRIC MOTOR UNIT CONTROL SYSTEM CIRCUIT
DIAGNOSIS CODE SET CONDITIONS
If the MCU detects the diagnosis code No. P1A2A IGBT overcurrent (MCU) 3 times in 60 seconds,
it will set the diagnosis code No. P0A78.
PROBABLE CAUSES
- Damaged high-voltage harness wires
- Malfunction of the motor (electric motor unit)
- Malfunction of the MCU
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STEP 1. M.U.T.-III CAN bus diagnosis
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Use the M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 3.
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 Repair the CAN bus line. (Refer to GROUP 54C - Troubleshooting  .)
Then go to Step 2.
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STEP 2. Diagnosis code recheck
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Check again if the diagnosis code is set to the MCU.
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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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Go to Step 3.
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The diagnosis is complete.
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STEP 3. ?Check whether the diagnosis code is set.
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Check if the diagnosis code No. P1A2A for other systems is set to the MCU.
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Q.
Is the diagnosis code set?
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Carry out troubleshooting for the diagnosis code No. P1A2A. (Refer to .)
Then go to Step 4.
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Go to Step 4.
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STEP 4. High-voltage connector check: G-07, G-08, G-09 MCU high-voltage
terminal
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Carry out the check on the high-voltage circuit while reading
carefully the precautions on handling a high-voltage vehicle. (Refer to .)
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Wear the specified protection equipment during the check.
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(1)Shut down the high voltage.
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(2)Check that the following terminals are tightened to the specified torque. (Refer
to .)
- G-07, G-08, G-09 MCU high-voltage terminal
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Q.
Is the check result normal?
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Go to Step 5.
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Tighten the high-voltage terminal to the specified torque. (Refer to .)
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STEP 5. Diagnosis code recheck
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Check again if the diagnosis code is set to the MCU.
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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 MCU.(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 MCU.
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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 motor (electric motor unit). (Refer to .)
Then go to Step 7.
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The diagnosis is complete.
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STEP 7. Diagnosis code recheck
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Check again if the diagnosis code is set to the MCU.
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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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Go to Step 1.
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The diagnosis is complete.
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