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DTC C1073 Motor Drive Circuit
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC 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.
 
 
OPERATION
  • ASC-ECU contains the power supply circuit (+BM terminal) for the pump motor. The pump motor is energized by the motor switch, which is incorporated in ASC-ECU.
  • The pump motor switch, which is incorporated in ASC-ECU, is always off unless the motor solenoid valve check is activated when the vehicle is started.
  • ASC-ECU activates the pump motor by turning on the ECU built-in pump motor switch.
 
 
 
DTC SET CONDITIONS
If the pump motor switch voltage drop indicates high value when the pump motor operates or after the operation, the pump motor operation is stopped and this DTC is set.
 
 
 
PROBABLE CAUSES
Current trouble
  • Fusible link malfunction
  • Damaged wiring harness and connectors
  • Abnormality in battery or generator
  • ASC-ECU malfunction
Past trouble
  • Carry out diagnosis with particular emphasis on wiring harness and connector failures between the power supply circuit (+BM terminal) to the ASC-ECU motor and the ground circuit (GND1, GND2 terminal). For diagnostic procedures, refer to How to treat past trouble (GROUP 00 - How to Use Troubleshooting/How to Treat Past Trouble ).
 
 
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
STEP 1. Battery check
Refer to GROUP 54A - Battery Test .
  • Also check the terminals for looseness and dirt.
Is the battery in good condition?
Go to Step 2.
Charge or replace or repair the battery (Refer to GROUP 54A - Battery ).
 
STEP 2. Fusible link check: Check the fusible link No.3.
Visually check for open circuit in the fusible link No.3.
Is the check result normal?
Go to Step 4.
Go to Step 3.
 
STEP 3. Resistance measurement at ASC-ECU connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Disconnect the fusible link No.3.
(3) Resistance between the +BM terminal and the body ground.
OK: No continuity
Is the check result normal?
Replace the fusible link No.3.
The short circuit may be present in the power supply circuit. Repair the wiring harness between the ASC-ECU connector +BM terminal and the fusible link, and then replace the fusible link No.3.
 
STEP 4. Voltage measurement at the ASC-ECU connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the voltage between the +BM terminal and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 5.
The open circuit may be present in the power supply circuit. Repair the wiring harness between the ASC-ECU connector +BM terminal and the fusible link.
 
STEP 5. Resistance measurement at ASC-ECU connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Resistance between the GND1 terminal and the body ground, and between the GND2 terminal and the body ground.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 6.
An open circuit may be present in the ground circuit. Repair the wiring harness between the ASC-ECU connector GND1 terminal and the body ground, and between the ASC-ECU connector GND2 terminal and the body ground.
 
STEP 6. Check whether the DTC is set again.
(1) Erase the DTC.
(2) Turn the ignition switch to the "LOCK" (OFF) position.
(3) Turn the ignition switch to the "ON" position.
(4) Drive the vehicle at 20 km/h (12 mph) or higher.
noteThe ABS warning light does not turn OFF in some cases unless the vehicle runs at 20 km/h (12 mph) or higher.
Is diagnostic trouble code No. C1073 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).