Code No. C1271: Motor drive circuit
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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.
- When you replace the electric parking brake actuator, use the M.U.T.-III to initialise learnt value for the actuator (Refer to ).
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OPERATION
- The electric parking brake ECU incorporates the power supply circuit for the electric parking brake actuator. The actuator (electric motor) is energised through the electric motor relay, which is incorporated in the ECU.
- To apply or release the parking brake, the electric parking brake ECU drives the electric motor by turning on the electric motor relay.
DIAGNOSIS CODE SET CONDITIONS
If the electric parking brake actuator (electric motor) drive circuit is open or short to earth, the diagnosis code will be set.
PROBABLE CAUSES
- electric parking brake actuator (electric motor) fails
- The wires or connector(s) in the electric parking brake actuator fail
- 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)Check the electric parking brake ECU connector.
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(2)Disconnect the connector and measure at the wiring harness side.
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(3)Measure the resistance between M+ terminal and M- terminal.
OK: 4 Ω or less
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(4)Measure the resistance between M+ terminal and body earth.
OK: No continuity
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Q.
Is the check result normal?
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 Go to Step 2.
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 Replace the electric parking brake actuator (Refer to ).
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STEP 2. Check whether the diagnosis code is set again.
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Check again if the diagnosis code is set.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch to the LOCK (OFF) position.
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(3)Turn the ignition switch to the ON position.
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(4)Check if the diagnosis code is set.
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Q.
Is diagnosis code No. C1271 set?
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Replace the electric parking brake ECU (Refer to ).
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The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
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