Anti-Lock Braking System (ABS)

DTC C1011: Abnormality in FL wheel speed sensor signal









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 CAN Bus Line Diagnostics Flow.
- 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 signals from each wheel speed sensor while the vehicle is being driven.
If any fault below is found in these sensor signals, ABS-ECU will set the relevant DTC.

- Irregular change in the wheel speed sensor signal
- Wheel speed sensor signal continuously indicates high value.

PROBABLE CAUSES

Current trouble

- Excessive gap between the wheel speed sensor and the magnetic encoder for wheel speed detection
- Adhesion of foreign materials on the wheel speed sensor
- Adhesion of foreign materials on the magnetic encoder for wheel speed detection
- Wheel bearing malfunction
- Malfunction of wheel speed sensor
- Damaged wiring harness and connectors
- External noise interference
- Improper installation of the wheel speed sensor
- Deformation of the magnetic encoder for wheel speed detection
- Malfunction of ABS-ECU
- Disturbance of magnetization pattern for magnetic encoder for wheel speed detection
- The number of poles on the magnetic encoder for wheel speed detection (the number of N-pole and S-pole) is changed.

Past trouble

- When the DTC C100A is also set, 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 How to Treat Past Trouble.
- When the DTC C100A is not set, the following conditions may be present:
- Some wheels slip
- Unstable vehicle attitude
- External noise interference
- Vehicle ran with the parking brake applied.

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

STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.

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 CAN Bus Diagnostics Chart).
On completion, go to Step 2.
STEP 2. DTC recheck after resetting CAN bus lines

Q. Is DTC C1011 set?

YES Go to Step 3.
NO The procedure is complete.
STEP 3. Using scan tool MB991958, check the DTC

Check that the DTC C100A is also set.

Q. Is DTC C100A also set?

YES Perform the diagnosis for the DTC C100A (Refer to Anti-Lock Braking System (ABS)).
NO Go to Step 4.
STEP 4. Connector check: A-03 ABS-ECU connector, A-07 front wheel speed sensor (LH) connector

Q. Is the check result normal?

YES Go to Step 5.
NO Repair the defective connector. Then go to Step 12.
STEP 5. Wiring harness check between A-03 ABS-ECU connector terminal No.18 and A-07 front wheel speed sensor (LH) connector terminal No.1, and between A-03 ABS-ECU connector terminal No.19 and A-07 front wheel speed sensor (LH) connector terminal No.2.

Q. Is the check result normal?

YES Go to Step 6.
NO Repair the wiring harness. Then go to Step 12.
STEP 6. Check wheel speed sensor [FL]
installation

Check how the wheel speed sensor [FL]
is installed (Disconnection of wheel speed sensor [FL], loose mounting bolt, etc.).

Q. Is the check result normal?

YES Go to Step 7.
NO Reinstall the wheel speed sensor [FL]
(Refer to Anti-Lock Braking System (ABS)). Then go to Step 7.
STEP 7. Check for wheel speed sensor [FL]
output current

Refer to Wheel Speed Sensor Output Current Measurement.

Q. Is the check result normal?

YES Go to Step 8.
NO Replace the wheel speed sensor [FL]
(Refer to Anti-Lock Braking System (ABS)).
Then go to Step 11.
STEP 8. Check for wheel bearing looseness

NOTE:

- Loose wheel bearing may increase the gap between the wheel speed sensor [FL] and the wheel speed detection magnet encoder.
- Check the wheel bearing [FL] for looseness Front Axle.

Q. Is the check result normal?

YES Go to Step 9.
NO Replace the wheel bearing [FL]
Removal and Replacement). Then go to Step 12.
STEP 9. Check wheel speed detection encoder





Check the encoder for adhesion of foreign materials or deformation.

Q. Is the check result normal?

YES Go to Step 10.

NO (Adhesion of foreign materials) : Remove the foreign materials and clean the encoder so as not to disturb the magnetization pattern on it while taking care of the magnet, magnetic substance, and magnetic attraction.
Then go to Step 12.

NO (Deformation) : Replace the wheel bearing [FL]
Removal and Replacement). Then go to Step 12.

STEP 10. Check whether the DTC is reset.

(1)Erase the DTC.

(2)Drive the vehicle at 12mph (20 km/h) or higher.
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 C1011 set?

YES Replace the wheel speed sensor [FL]
(Refer to Anti-Lock Braking System (ABS)). Then go to Step 11.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 11. Check whether the DTC is reset.

(1)Erase the DTC.

(2)Drive the vehicle at 12mph (20 km/h) or higher.
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 C1011 set?

YES Replace the hydraulic unit (integrated with ABS-ECU) (Refer to Anti-Lock Braking System (ABS)).
Then go to Step 12.
NO The procedure is complete.
STEP 12. Check whether the DTC is reset.

(1)Erase the DTC.

(2)Drive the vehicle at 12mph (20 km/h) or higher.
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 C1011 set?

YES Return to Step 1.
NO The procedure is complete.