Code No. C1860: Power supply high 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 - Troubleshooting
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- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
- When the hydraulic unit assembly (integrated with ASTC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G sensor (Refer to ).
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OPERATION
The ASTC-ECU is energised by the ignition switch through the multi-purpose fuse at the terminal IG1.
DIAGNOSIS CODE SET CONDITIONS
The ASTC-ECU monitors the ASTC-ECU power supply voltage sent from the battery. When the voltage exceeds a predetermined value, the ECU determines that the trouble occurs and sets the diagnosis code.
PROBABLE CAUSES
Current trouble
- Overcurrent
- Battery failure
- Charging system failed
- Damaged harness wires and connectors
- Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)
Past trouble
- Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the power supply circuit (+BV and IG1 terminals) to the ASTC-ECU. For diagnosis procedures, refer to How to treat past trouble (GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).
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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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Q.
Is diagnosis code No. C1860 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 battery 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 5.
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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 charging system in good condition?
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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 5.
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STEP 5. Measure the resistance at the ASTC-ECU-ECU connector.
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(1)Connector check: the ASTC-ECU connector, the fuses (relay box) and the fusible links
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(2)Disconnect the ASTC-ECU connector.
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(3)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 ASTC-ECU connector +BV terminal and the fusible links, the fuse (relay box) or the fusible links. Then go to Step 7.
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STEP 6. Measure the resistance at the ASTC-ECU connector.
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(1)Check the connectors and the junction block.
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(2)Disconnect the ASTC-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 7.
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The power supply circuit may be short. Repair the wiring harness wires or connectors between the ASTC-ECU connector IG1 terminal and the junction block. Then go to Step 7.
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STEP 7. 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 set diagnosis code.
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(2)Ignition switch: "LOCK" (OFF)
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Q.
Is diagnosis code No. C1860 set?
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Replace the hydraulic unit assembly (integrated with ASTC-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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