Code No. C1861: Power supply low voltage
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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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OPERATION
The electric parking brake ECU is energised from the battery through the fusible links.
DIAGNOSIS CODE SET CONDITIONS
If the parking brake is not applied or released within a predetermined period due to a low battery voltage, the diagnosis code will be set.
PROBABLE CAUSES
- Battery not charged sufficiently or deteriorated
- Loose or contaminated battery terminals
- Open or earth fault in the electric parking brake ECU power supply circuit.
- Malfunction of the electric parking brake ECU
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STEP 1. Check the battery.
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Refer to GROUP 54A - Battery Test .
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Q.
Is the check result normal?
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 Go to Step 2.
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 Charge or replace the battery (Refer to GROUP 54A - Battery ). Then go to Step 3.
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STEP 2. Check the charging system.
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Refer to GROUP 16 - Charging System .
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Q.
Is the check result normal?
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Go to Step 3.
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Repair or replace the charging system component(s) (Refer to GROUP 16 - Alternator ). Then go to Step 3.
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STEP 3. 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 GND1 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 4.
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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. Then go to Step 4.
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STEP 4. 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 BECU terminal and body earth.
OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 5.
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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. Then go to Step 5.
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STEP 5. 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. C1861 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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