ABS

DTC C1015: Abnormality in FR 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.
^ Whenever ECU is replaced, ensure that the CAN bus lines are normal.

CIRCUIT 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 ABS-ECU. ABS-ECU uses the frequency of the pulse signals to determine the wheel speed.

DTC SET CONDITIONS
ABS-ECU monitors the voltage fluctuation in each wheel speed sensor circuit. If ABS-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 ABS-ECU

Past trouble
^ Carry out diagnosis with particular emphasis on wiring harness and connector failures between ABS-ECU and the wheel speed sensor. For diagnosis procedures, refer to How to treat past trouble.

DIAGNOSIS

Required Special Tools:
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
^ MB991974: ABS check harness

STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.

Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. On completion, go to Step 2.

STEP 2. DTC recheck after resetting CAN bus lines

Q: Is the DTC C1015 set?
YES: Go to Step 3.
NO: The procedure is complete.

STEP 3. M.U.T.-III data list
Check the following service data.
^ Item No.02: FR wheel speed sensor

Q: Is the check result normal?
YES: Go to Step 12.
NO: Go to Step 4.

STEP 4. Voltage measurement at the A-03 ABS-ECU connector





1) Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and then measure the voltage at the special tool connector side.

NOTE: Do not connect the special tool to ABS-ECU.

2) Turn the ignition switch to the ON position.
3) Measure the voltage between the wheel speed sensor power supply terminal (signal terminal) No.22 and body ground, and between the ground terminal No.21 and body ground.
OK: 1 volt or less

Q: Is the check result normal?
YES: Go to Step 5.
NO (Not normal at the terminal No.22 or 21): Go to Step 6.

STEP 5. Resistance measurement at A-03 ABS-ECU connector





1) Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and then measure the resistance at the special tool connector side.

NOTE: Do not connect the special tool to ABS-ECU.

2) Resistance between the wheel speed sensor power supply terminal (signal terminal) No.22 and body ground, and between the ground terminal No.21 and body ground.
OK: No continuity

Q: Is the check result normal?
YES: Go to Step 8.
NO (Not normal at the terminal No.22 or 21): Go to Step 6.

STEP 6. Connector check: A-03 ABS-ECU connector, A-02 wheel speed sensor [FR] connector

Q: Is the check result normal?
YES: Go to Step 7.
NO: Repair the defective connector. Then go to Step 13.

STEP 7. Wiring harness check between A-03 ABS-ECU connector terminal No.22 and A-02 wheel speed sensor [FR] connector terminal No.1, and between A-03 ABS-ECU connector terminal No.21 and A-02 wheel speed sensor [FR] connector terminal No.2.
^ Check for short circuit in wheel speed sensor [FR] circuit

Q: Is the check result normal?
YES: Replace the wheel speed sensor [FR]. Then go to Step 13.
NO: Repair the wiring harness. Then go to Step 13.

STEP 8. Voltage measurement at the A-03 ABS-ECU connector





1) Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the ABS-ECU-side connector and harness-side connector, and then measure the voltage at the special tool connector side.
2) Turn the ignition switch to the ON position.
3) Measure the voltage between the wheel speed sensor circuit power supply terminal (signal terminal) No.22 and body ground.
OK: Battery positive voltage

Q: Is the check result normal?
YES: Go to Step 9.
NO: Go to Step 11.

STEP 9. Wiring harness check between A-03 ABS-ECU connector terminal No.22 and A-02 wheel speed sensor [FR] connector terminal No.1, and between A-03 ABS-ECU connector terminal No.21 and A-02 wheel speed sensor [FR] connector terminal No.2.
^ Check for open circuit in wheel speed sensor [FR] circuit

Q: Is the check result normal?
YES: Go to Step 10.
NO: Repair the wiring harness. Then go to Step 13.

STEP 10. Check for wheel speed sensor as a single unit

Q: Is the check result normal?
YES: Go to Step 11.
NO: Replace the wheel speed sensor.

STEP 11. Connector check: A-03 ABS-ECU connector, A-02 wheel speed sensor [FR] connector

Q: Is the check result normal?
YES: Go to Step 12.
NO: Repair the defective connector. Then go to Step 13.

STEP 12. Check whether the DTC is reset.
1) Erase the DTC.
2) Drive the vehicle at 12mph (20 km/h) or more.

NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12mph (20 km/h) or higher.

Q: Is DTC C1015 set?
YES: Replace the hydraulic unit (ASC-ECU). Then go to Step 13.
NO: Intermittent malfunction.

STEP 13. Check whether the DTC is reset.
1) Erase the DTC.
2) Drive the vehicle at 12mph (20 km/h) or more.

NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12mph (20 km/h) or higher.

Q: Is DTC C1015 set?
YES: Return to Step 1.
NO: The procedure is complete.