[Previous][Next]
Inspection Procedure 1: scan tool (M.U.T.-IIISE) communication with the ABS/ASC system is impossible.
 
 
caution
  • When the ASC-ECU power supply voltage becomes 9.7 ± 0.3 V or less, the ABS warning light, ASC warning display, and ASC OFF display illuminate, and the ABS, stability control, and TCL controls are prohibited.
  • If the battery terminal is not tightened properly, a dump surge may occur and the power supply voltage may become abnormally high for a short time.
  • 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 (+BV terminal) for the solenoid valve. The solenoid valve is energized by the valve relay, which is incorporated in ASC-ECU.
  • ASC-ECU contains the power supply circuit (IG1 terminal) for ASC-ECU. When the ignition switch is turned ON, the voltage is applied to the relay incorporated in ETACS-ECU to turn ON the relay, and the power is supplied from the fusible link.
  • When malfunction occurs in ASC-ECU power supply, the communication with scan tool (M.U.T.-IIISE) becomes unavailable.
 
 
 
PROBABLE CAUSES
  • Damaged wiring harness and connectors of power supply and ground
  • Fusible link malfunction
  • ASC-ECU malfunction
 
 
 
 
DIAGNOSIS
STEP 1. Fusible link check: Check the fusible link No.4.
Visually check for open circuit in the fusible link No.4.
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Resistance measurement at ASC-ECU connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Disconnect the fusible link No.4.
(3) Resistance between the +BV terminal and the body ground.
OK: No continuity
Is the check result normal?
Replace the fusible link No.4.
The short circuit may be present in the power supply circuit. Repair the wiring harness between the ASC-ECU connector +BV terminal and the fusible link, and then replace the fusible link No.4.
 
STEP 3. Voltage measurement at the ASC-ECU connector
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the voltage between the +BV terminal and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 4.
The open circuit may be present in the power supply circuit. Repair the wiring harness between the ASC-ECU connector +BV terminal and the fusible link No.4.
 
STEP 4. Voltage measurement at the ASC-ECU connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between ASC-ECU connector (IG1 terminal) and body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 6.
Go to Step 5.
 
STEP 5. Check of short to power supply, short to ground, and open circuit in IG1 line between ETACS-ECU and ASC-ECU connector.
Is the check result normal?
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 6. Resistance measurement at ASC-ECU connector.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Resistance between the ASC-ECU connector (GND1 terminal) and the body ground, and between the ASC-ECU connector (GND2 terminal) and the body ground
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 8.
Go to Step 7.
 
STEP 7. Check of open circuit in GND1, GND2 line between ASC-ECU connector and body ground.
Is the check result normal?
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 8. Retest the system.
Is the communication with scan tool (M.U.T.-IIISE) possible?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).