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DTC C100A FL Wheel Speed Sensor Circuit
DTC C1015 FR Wheel Speed Sensor Circuit
DTC C1020 RL Wheel Speed Sensor Circuit
DTC C102B RR Wheel Speed Sensor 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
  • The wheel speed sensor is a kind of a pulse generator. It consists of encoders (a plate on which north and south pole sides of the magnets are arranged alternately) for detecting the wheel speed which rotates at the same speed of the wheels and wheel speed sensors. This sensor outputs frequency pulse signals in proportion to the wheel speed.
  • The pulse signals, which the wheel speed sensor creates, are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.
 
 
 
DTC SET CONDITIONS
ASC-ECU monitors the voltage fluctuation in each wheel speed sensor circuit. If ASC-ECU detects the open or short circuit in the circuit, it will set a DTC.
 
 
 
PROBABLE CAUSES
Current trouble
  • Damaged wiring harness and connectors
  • Noise interference
  • Malfunction of wheel speed sensor
  • Malfunction of ASC-ECU
Past trouble
  • Carry out diagnosis with particular emphasis on wiring harness and connector failures between ASC-ECU and the wheel speed sensor. 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. Voltage measurement at the ASC-ECU connector (FL+, FL-, FR+, FR-, RL+, RL-, RR+, RR- terminal)
(1) Disconnect the ASC-ECU connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "ON" position.
DTC C100A is set
  • Measure the voltage between the ASC-ECU connector (FL+ terminal) and the body ground, and between the ASC-ECU connector (FL- terminal) and the body ground.
OK: 1 volt or less
DTC C1015 is set
  • Measure the voltage between the ASC-ECU connector (FR+ terminal) and the body ground, and between the ASC-ECU connector (FR- terminal) and the body ground.
OK: 1 volt or less
DTC C1020 is set
  • Measure the voltage between the ASC-ECU connector (RL+ terminal) and the body ground, and between the ASC-ECU connector (RL- terminal) and the body ground.
OK: 1 volt or less
DTC C102B is set
  • Measure the voltage between the ASC-ECU connector (RR+ terminal) and the body ground, and between the ASC-ECU connector (RR- terminal) and the body ground.
OK: 1 volt or less
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Voltage measurement at the ASC-ECU connector.
(1) Disconnect the ASC-ECU connector and wheel speed sensor connector, and measure at the wiring harness side of the ASC-ECU connector.
(2) Turn the ignition switch to the "ON" position.
DTC C100A is set
  • Measure the voltage between the ASC-ECU connector (FL+ terminal) and the body ground, and between the ASC-ECU connector (FL- terminal) and the body ground.
OK: 1 volt or less
DTC C1015 is set
  • Measure the voltage between the ASC-ECU connector (FR+ terminal) and the body ground, and between the ASC-ECU connector (FR- terminal) and the body ground.
OK: 1 volt or less
DTC C1020 is set
  • Measure the voltage between the ASC-ECU connector (RL+ terminal) and the body ground, and between the ASC-ECU connector (RL- terminal) and the body ground.
OK: 1 volt or less
DTC C102B is set
  • Measure the voltage between the ASC-ECU connector (RR+ terminal) and the body ground, and between the ASC-ECU connector (RR- terminal) and the body ground.
OK: 1 volt or less
Is the check result normal?
Replace the wheel speed sensor (Refer to <front> or <rear>).
Repair the connector(s) or wiring harness.
 
STEP 3. Resistance measurement at ASC-ECU connector (FL+, FL-, FR+, FR-, RL+, RL-, RR+, RR- terminal)
Disconnect the ASC-ECU connector, and measure at the wiring harness side of the ASC-ECU connector.
DTC C100A is set
  • Measure the resistance between the ASC-ECU connector (FL+ terminal) and the body ground, and between the ASC-ECU connector (FL- terminal) and the body ground.
OK: No continuity
DTC C1015 is set
  • Measure the resistance between the ASC-ECU connector (FR+ terminal) and the body ground, and between the ASC-ECU connector (FR- terminal) and the body ground.
OK: No continuity
DTC C1020 is set
  • Measure the resistance between the ASC-ECU connector (RL+ terminal) and the body ground, and between the ASC-ECU connector (RL- terminal) and the body ground.
OK: No continuity
DTC C102B is set
  • Measure the resistance between the ASC-ECU connector (RR+ terminal) and the body ground, and between the ASC-ECU connector (RR- terminal) and the body ground.
OK: No continuity
Is the check result normal?
Go to Step 5.
Go to Step 4.
 
STEP 4. Resistance measurement at ASC-ECU connector.
Disconnect the ASC-ECU connector and wheel speed sensor connector, and measure at the wiring harness side of the ASC-ECU connector.
DTC C100A is set
  • Measure the resistance between the ASC-ECU connector (FL+ terminal) and the body ground, and between the ASC-ECU connector (FL- terminal) and the body ground.
OK: No continuity
DTC C1015 is set
  • Measure the resistance between the ASC-ECU connector (FR+ terminal) and the body ground, and between the ASC-ECU connector (FR- terminal) and the body ground.
OK: No continuity
DTC C1020 is set
  • Measure the resistance between the ASC-ECU connector (RL+ terminal) and the body ground, and between the ASC-ECU connector (RL- terminal) and the body ground.
OK: No continuity
DTC C102B is set
  • Measure the resistance between the ASC-ECU connector (RR+ terminal) and the body ground, and between the ASC-ECU connector (RR- terminal) and the body ground.
OK: No continuity
Is the check result normal?
Replace the wheel speed sensor (Refer to <front> or <rear>).
Repair the connector(s) or wiring harness.
 
STEP 5. Resistance measurement at ASC-ECU connector.
Disconnect the ASC-ECU connector and wheel speed sensor connector, and measure at the wiring harness side of the ASC-ECU connector.
DTC C100A is set
  • Measure the resistance between the ASC-ECU connector (FL+ terminal) and (FL- terminal).
OK: No continuity
DTC C1015 is set
  • Measure the resistance between the ASC-ECU connector (FR+ terminal) and (FR- terminal).
OK: No continuity
DTC C1020 is set
  • Measure the resistance between the ASC-ECU connector (RL+ terminal) and (RL- terminal).
OK: No continuity
DTC C102B is set
  • Measure the resistance between the ASC-ECU connector (RR+ terminal) and (RR- terminal).
OK: No continuity
Is the check result normal?
Go to Step 6.
Repair the connector(s) or wiring harness.
 
STEP 6. Voltage measurement at the wheel speed sensor connector.
(1) Disconnect the wheel speed sensor connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "ON" position.
DTC C100A is set
  • Measure the voltage between the wheel speed sensor connector (FL+ terminal) and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
DTC C1015 is set
  • Measure the voltage between the wheel speed sensor connector (FR+ terminal) and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
DTC C1020 is set
  • Measure the voltage between the wheel speed sensor connector (RL+ terminal) and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage)
DTC C102B is set
  • Measure the voltage between the wheel speed sensor connector (RR+ terminal) and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 8.
Go to Step 7.
 
STEP 7. Resistance measurement at ASC-ECU connector and wheel speed sensor.
Disconnect the ASC-ECU connector and wheel speed sensor connector, and measure at the wiring harness side of the ASC-ECU connector and wheel speed sensor connector.
DTC C100A is set
  • Check of open circuit in FL+ line between ASC-ECU connector and front wheel speed sensor (LH) connector.
OK: The resistance should be 2 ohms or less
DTC C1015 is set
  • Check of open circuit in FR+ line between ASC-ECU connector and front wheel speed sensor (RH) connector.
OK: The resistance should be 2 ohms or less
DTC C1020 is set
  • Check of open circuit in RL+ line between ASC-ECU connector and rear wheel speed sensor (LH) connector.
OK: The resistance should be 2 ohms or less
DTC C102B is set
  • Check of open circuit in RR+ line between ASC-ECU connector and rear wheel speed sensor (RH) connector.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 11.
Repair the connector(s) or wiring harness.
 
STEP 8. Current measurement at each wheel speed sensors connector.
Refer to .
Is the check result normal?
Go to Step 11.
Go to Step 9.
 
STEP 9. Resistance measurement at ASC-ECU connector and wheel speed sensor.
Disconnect the ASC-ECU connector and wheel speed sensor connector, and measure at the wiring harness side of the ASC-ECU connector and wheel speed sensor connector.
DTC C100A is set
  • Check of open circuit in FL- line between ASC-ECU connector and front wheel speed sensor (LH) connector.
OK: The resistance should be 2 ohms or less
DTC C1015 is set
  • Check of open circuit in FR- line between ASC-ECU connector and front wheel speed sensor (RH) connector.
OK: The resistance should be 2 ohms or less
DTC C1020 is set
  • Check of open circuit in RL- line between ASC-ECU connector and rear wheel speed sensor (LH) connector.
OK: The resistance should be 2 ohms or less
DTC C102B is set
  • Check of open circuit in RR- line between ASC-ECU connector and rear wheel speed sensor (RH) connector.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 10.
Repair the connector(s) or wiring harness.
 
STEP 10. Check for wheel speed sensor as a single unit
Refer to .
Is the check result normal?
Go to Step 11.
Replace the wheel speed sensor (Refer to <front> or <rear>).
 
STEP 11. 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 DTC C100A, C1015, C1020 or C102B 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 ).