Code No.C1861:
Low voltage at ABS-ECU power supply
caution |
- 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
).
- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
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OPERATION
- The ABS-ECU is energised by the ignition switch (IG1) through J/B
fuse.
- Power supply for ABS solenoid valve is supplied to the ABS-ECU via fusible link.
- Power supply for ABS motor is supplied to the ABS-ECU via fusible link.
- The wheel speed sensors are energised via ABS-ECU.
DIAGNOSIS CODE SET CONDITIONS
The ABS-ECU monitors the ABS-ECU power supply voltage sent from the battery. When the
voltage falls below a predetermined value, the ECU determines that the trouble occurs and sets
the diagnosis code.
PROBABLE CAUSES
- Battery failure
- Charging system failed
- Damaged harness wires and connectors
- Malfunction of the hydraulic unit assembly (integrated with ABS-ECU)
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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 .)
On completion, go to Step 2.
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STEP 2. Diagnosis code recheck after resetting CAN bus lines
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(1)Turn the ignition switch to the "LOCK" (OFF) position.
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(2)Turn the ignition switch to the "ON" position.
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(3)Erase the diagnosis code.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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(5)Turn the ignition switch to the "ON" position.
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(6)Check if the diagnosis code is set.
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Q.
Is diagnosis code No. C1861 set?
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Go to Step 3.
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This diagnosis is complete.
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STEP 3. 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 4.
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Charge or replace the battery (Refer to GROUP 54A - Battery ).
Then go to Step 13.
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STEP 4. 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 5.
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Repair or replace the charging system component(s) (Refer to GROUP 16 - Alternator ).
Then go to Step 13.
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STEP 5. Measure the resistance at the ABS-ECU connector.
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(1)Connector check: the ABS-ECU connector, the fuses (relay box) and the fusible links
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(2)Check the ABS-ECU connector.
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(3)Disconnect the connector and measure at the wiring harness side.
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(4)Measure the resistance between +BV terminal and body earth. OK: No continuity
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Q.
Is the check result normal?
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Go to Step 6.
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The power supply circuit may be short. Repair the wiring harness wires or connectors
between the ABS-ECU connector +BV terminal and the fusible links, the fuse (relay box)
or the fusible links. Then go to Step 13.
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STEP 6. Measure the resistance at the ABS-ECU connector.
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(1)Connector check: the ABS-ECU connector and the fusible links
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(2)Check the ABS-ECU connector.
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(3)Disconnect the connector and measure at the wiring harness side.
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(4)Measure the resistance between +BM terminal and body earth. OK: No continuity
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Q.
Is the check result normal?
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Go to Step 7.
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The power supply circuit may be short. Repair the wiring harness wires or connectors
between the ABS-ECU connector +BM terminal and the fusible links. Then go to Step 13
.
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STEP 7. Measure the resistance at the ABS-ECU connector.
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(1)Check the connectors and the junction block.
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(2)Disconnect the ABS-ECU connector.
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(3)Measure the resistance between the IG1 terminal and body earth. OK: No continuity
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Q.
Is the check result normal?
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Go to Step 8.
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The power supply circuit may be short. Repair the wiring harness wires or connectors
between the ABS-ECU connector IG1 terminal and the junction block. Then go to Step 13.
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STEP 8. Measure the voltage at the ABS-ECU connector.
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(1)Disconnect the ABS-ECU connector.
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(2)Measure the voltage between +BV terminal and body earth. OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 9.
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The power supply circuit may be open. Repair the wiring harness wires or connectors
between the ABS-ECU connector +BV terminal and the fusible links, the fuse (relay box)
or the fusible links. Then go to Step 13.
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STEP 9. Measure the voltage at the ABS-ECU connector.
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(1)Disconnect the ABS-ECU connector.
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(2)Measure the voltage between +BM terminal and body earth. OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 10.
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The power supply circuit may be open. Repair the wiring harness wires or connectors
between the ABS-ECU connector +BM terminal and the fusible links. Then go to Step 13
.
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STEP 10. Measure the voltage at the ABS-ECU connector.
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(1)Disconnect the ABS-ECU connector.
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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 11.
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The power supply circuit may be open. Repair the wiring harness wires or connectors
between the ABS-ECU connector IG1 terminal and the junction block. Then go to Step 13.
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STEP 11. Measure the resistance at the ABS-ECU connector.
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(1)Disconnect the ABS-ECU connector.
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(2) Measure the resistance between the GND1 terminal and body earth as well as between
the 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 12.
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The earth circuit may be open. Repair the wiring harness wires or connectors between
the ABS-ECU connector GND1 terminal and the fusible links as well as between the GND2 terminal
and the fusible links. Then go to Step 13.
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STEP 12. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "LOCK" (OFF) position.
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(2)Turn the ignition switch to the "ON" position.
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(3)Erase the diagnosis code.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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(5)Turn the ignition switch to the "ON" position.
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(6)Check if the diagnosis code is set.
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Q.
Is diagnosis code No. C1861 set?
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Replace the hydraulic unit assembly (integrated with ABS-ECU) (Refer to ).
Then go to Step 13.
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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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STEP 13. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "LOCK" (OFF) position.
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(2)Turn the ignition switch to the "ON" position.
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(3)Erase the diagnosis code.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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(5)Turn the ignition switch to the "ON" position.
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(6)Check if the diagnosis code is set.
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Q.
Is diagnosis code No. C1861 set?
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Return to Step 1.
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The procedure is complete.
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