Inspection Procedure
1: M.U.T.-III cannot communicate with electric parking brake system (the power supply to the
electric parking brake ECU fails).
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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,
diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table
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- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
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COMMENTS ON TROUBLE SYMPTOM
When M.U.T.-III cannot communicate with the electric parking brake system, the CAN bus
lines, electric parking brake ECU power supply circuit system, earth, or electric parking brake
ECU may be faulty.
PROBABLE CAUSES
- Open or earth fault in the electric parking brake ECU power supply circuit,
or defective connector(s)
- Malfunction of the electric parking brake ECU
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STEP 1. Measure the resistance at the electric parking brake
ECU connector.
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(1)Disconnect the connector and measure at the wiring harness side.
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(2)Measure the resistance between GND1 terminal and body earth.
OK: Continuity exists (2 Ω or less).
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(3)Measure the resistance between GND2 terminal and body earth.
OK: Continuity exists (2 Ω or less).
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Q.
Is the check result normal?
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 Go to Step 2.
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 The earth circuit may be open. Repair the wiring harness wires or connectors between
the electric parking brake ECU connector and the body earth.
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STEP 2. Measure the voltage at the electric parking brake ECU connector.
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(1)Disconnect the electric parking brake ECU connector.
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(2)Measure the voltage between the +ECU terminal and body earth.
OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 3.
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The power supply circuit may be open. Repair the wiring harness wires or connectors
between the electric parking brake ECU connector and the fusible link.
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STEP 3. Measure the voltage at the electric parking brake ECU connector.
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(1)Disconnect the electric parking brake ECU connector and measure at the wiring harness
side.
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(2)Turn the ignition switch to the ON position.
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(3)Measure the voltage between the IG1 terminal and body earth.
OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 4.
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The IG1 signal circuit may be open or short to earth. Repair the wiring harness
wires or connectors between the electric parking brake ECU connector and the ETACS-ECU (IG1
relay).
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STEP 4. Retest the system
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunction).
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Replace the electric parking brake ECU (Refer to ).
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