If there is
any problem in the CAN bus lines, an incorrect diagnosis code 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.
DIAGNOSIS CODE SET CONDITIONS
ASC-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, ASC-ECU will set the relevant diagnosis code.
Missing wheel speed sensor signal
Wheel speed sensor signal continuously indicates low value.
PROBABLE CAUSES
Current trouble
Excessive gap between the wheel speed sensor and the wheel speed detection encoder
Wheel bearing malfunction
Deformation of the wheel speed detection encoder
Adhesion of foreign materials on the wheel speed sensor
Adhesion of foreign materials on the wheel speed detection encoder
Malfunction of wheel speed sensor
Improper installation of the wheel speed sensor
ASC-ECU malfunction
The number of poles on the Magnetic encoder for wheel speed detection (N-pole and
S-pole) is changed
Past trouble
When diagnosis code No.C100A, C1015, C1020 or C102B is also set,
carry out diagnosis with particular emphasis on wiring harness and connector failures between
ASC-ECU and the wheel speed sensor. For diagnosis procedures, refer to How to treat past trouble
(GROUP 00 - How to Use Troubleshooting/How to Treat Past Trouble ).
When diagnosis code No.C100A, C1015, C1020 or C102B 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.
Rotate only two wheels with drum tester
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 3
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
On completion, go to Step 2.
STEP 2. Diagnosis code recheck after resetting CAN bus lines
Q.
Is the diagnosis code No.C1014, C101F, C102A or C1035 set?
Go to Step 3
This diagnosis is complete.
STEP 3. M.U.T.-III diagnosis code
Check that diagnosis code No.C100A, C1015, C1020 or C102B is also set.
Q.
Is diagnosis code No.C100A, C1015, C1020 or C102B also set?
Perform the diagnosis for diagnosis code No.C100A, C1015, C1020 or C102B (Refer
to ).
Go to Step 4
STEP 4. Check the wiring harness between the ASC-ECU connector terminal
and the wheel speed sensor connector terminal
Code No.C1014 is set
Check of short to power supply, short to earth, and open circuit in FL+,
FL- line between ASC-ECU connector and front wheel speed sensor (LH) connector.
Code No.C101F is set
Check of short to power supply, short to earth, and open circuit in FR+,
FR- line between ASC-ECU connector and front wheel speed sensor (RH) connector.
Code No.C102A is set
Check of short to power supply, short to earth, and open circuit in RL+,
RL- line between ASC-ECU connector and rear wheel speed sensor (LH) connector.
Code No.C1035 is set
Check of short to power supply, short to earth, and open circuit in RR+,
RR- line between ASC-ECU connector and rear wheel speed sensor (RH) connector.
Q.
Is the check result normal?
Go to Step 5
Repair the connector(s) or wiring harness. Then go to Step 11.
STEP 5. Check for wheel speed sensor installation
Check how the wheel speed sensor is installed (Disconnection of wheel speed sensor, loose
mounting bolt, etc.).
Q.
Is the check result normal?
Go to Step 6
Reinstall the wheel speed sensor correctly (Refer to <front> or <rear>).
Then go to Step 6.
STEP 6. Check for wheel speed sensor output current
Refer to .
Q.
Is the check result normal?
Go to Step 7
Replace the wheel speed sensor (Refer to <front> or <rear>).
Then go to Step 10.
STEP 7. Check for wheel bearing looseness
note
Loose wheel bearing may increase the gap between the wheel speed sensor and the wheel
speed detection magnet encoder. Check the wheel bearing for looseness. <Refer to GROUP
26 - Wheel Bearing Axial Play Check . (front),
GROUP 27A - Wheel Bearing Axial Play Check (rear-2WD)
or GROUP 27B - Wheel Bearing Axial Play Check (rear-4WD)>
Q.
Is the check result normal?
Go to Step 8
Replace the wheel bearing <front> or rear wheel hub assembly <rear>. <Refer
to GROUP 26 - Front Axle Hub Assembly (front),
GROUP 27A - Rear Axle Hub Assembly (rear-2WD)
or GROUP 27B - Rear Axle Hub Assembly (rear-4WD)> Then
go to Step 11.
STEP 8. Check of wheel speed detection encoder
Check the encoder for adhesion of foreign materials or deformation.
Q.
Is the check result normal?
Go to Step 9
NO (Adhesion of foreign materials) : Remove the foreign materials and clean the encoder so as not to disturb the magnetisation
pattern on it while taking care of the magnet, magnetic substance, and magnetic attraction.
Then go to Step 9.
NO (Deformation) : Replace the wheel bearing <front> or rear wheel hub assembly <rear>. <Refer
to GROUP 26 - Front Axle Hub Assembly (front), GROUP
27A - Rear Axle Hub Assembly (rear-2WD) or GROUP
27B - Rear Axle Hub Assembly (rear-4WD)> Then
go to Step 9.
STEP 9. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note
The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h
or higher.
Q.
Is diagnosis code No. C1014, C101F, C102A or C1035 set?
Replace the wheel speed sensor (Refer to <front> or <rear>).
Then go to Step 10.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How
to Cope with Intermittent Malfunctions ).
STEP 10. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note
The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h
or higher.
Q.
Is diagnosis code No. C1014, C101F, C102A or C1035 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).
Then go to Step 11.
This diagnosis is complete.
STEP 11. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or higher.
note
The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h
or higher.
Q.
Is diagnosis code No. C1014, C101F, C102A or C1035 set?