Code No. C1201
Abnormality in FR wheel speed sensor signal Code No. C1206 Abnormality in FL wheel
speed sensor signal Code No. C1211 Abnormality in RR wheel speed sensor signal Code
No. C1216 Abnormality in RL wheel speed sensor signal
caution
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 ).
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.
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 wheel speed detection encoder
Adhesion of foreign materials on the wheel speed sensor
Adhesion of foreign materials on the wheel speed detection encoder
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 wheel speed detection encoder
ASC-ECU malfunction
Disturbance of magnetisation pattern for wheel speed detection encoder
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 diagnosis code No.C1200, C1205, C1210, C1215 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 Cope with Intermittent Malfunctions ).
When diagnosis code No.C1200, C1205, C1210, C1215 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 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.C1201, C1206, C1211, C1216 set?
Go to Step 3.
The procedure is complete.
STEP 3. M.U.T.-III diagnosis code
Check that the diagnosis code No.C1200, C1205, C1210, C1215 is also set.
Q.
Is the diagnosis code No.C1200, C1205, C1210, C1215 also set?
Perform the diagnosis for the diagnosis code No.C1200, C1205,
C1210, C1215 (Refer to ).
Go to Step 4
STEP 4. Check for wheel speed sensor installation
Check how the wheel speed sensor is installed (Disconnection of wheel speed sensor, loose
mounting bolt, etc.).
Diagnosis code
Wheel speed sensor
C1201
FR
C1206
FL
C1211
RR
C1216
RL
Q.
Is the check result normal?
Go to Step 5.
Reinstall the wheel speed sensor correctly (Refer to ).
STEP 5. Check for wheel speed sensor as a single unit
Refer to .
Q.
Is the check result normal?
Go to Step 6.
Replace the wheel speed sensor (Refer to ).
STEP 6. Check for wheel bearing looseness
note
If the wheel bearing are loose, the gap between the wheel speed sensor and magnetic encoder
may become excessive. Check the wheel bearing, which diagnosis code indicates, for looseness.
Diagnosis code
Wheel speed sensor
C1201
FR
C1206
FL
C1211
RR
C1216
RL
Front: Refer to GROUP 26 -On-vehicle Service .
Rear: Refer to GROUP 27 -On-vehicle Service .
Q.
Is the check result normal?
Go to Step 7.
NO <Front> : Replace the hub knuckle assembly (Refer to GROUP 26 - Front
Axle Hub Assembly ).
NO <Rear> : Replace the rear wheel hub assembly (Refer to GROUP 27 - Rear
Axle Hub Assembly ).
STEP 7. 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 8.
NO <Front> : 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. When the encoder is deformed, replace the hub knuckle assembly (Refer
to GROUP 26 - Front Axle Hub Assembly ).
NO <Rear> : 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. When the encoder is deformed, replace the rear wheel hub assembly (Refer
to GROUP 27 - Rear Axle Hub Assembly ).
STEP 8. Voltage measurement at the A-14 ASC-ECU connector
(1)Disconnect the ASC-ECU connector, connect special tool ABS check harness (MB992335)
to the harness-side connector, and then measure the voltage at the special tool connector side.
note
Do not connect the special tool ABS check harness (MB992335) to ASC-ECU.
(2)Turn the electric motor switch to the "ON" position. (3)Measure the voltage between the front wheel speed sensor power supply terminal
and the body earth, and between the front wheel speed sensor signal terminal and the body earth.
Diagnosis code No.
Check terminal
Power supply terminal
Signal terminal
C1201
No. 18
No. 6
C1206
No. 34
No. 22
C1211
No. 19
No. 31
C1216
No. 33
No. 20
OK: 1 volt or less
Q.
Is the check result normal?
Go to Step 9.
NO (Not normal at the terminal No. 18 or 6) : Go to Step 10.
NO (Not normal at the terminal No. 34 or 22) : Go to Step 11.
NO (Not normal at the terminal No. 19 or 31) : Go to Step 12.
NO (Not normal at the terminal No. 33 or 20) : Go to Step 13.
STEP 9. Resistance measurement at A-14 ASC-ECU connector
(1)Disconnect the ASC-ECU connector, connect special tool ABS check harness (MB992335)
to the harness-side connector, and then measure the resistance at the special tool connector
side.
note
Do not connect the special tool ABS check harness (MB992335) to ASC-ECU.
(2)Measure the resistance between the front wheel speed sensor power supply terminal
and the body earth, and between the front wheel speed sensor signal terminal and the body earth.
Diagnosis code No.
Check terminal
Power supply terminal
Signal terminal
C1201
No. 18
No. 6
C1206
No. 34
No. 22
C1211
No. 19
No. 31
C1216
No. 33
No. 20
OK: No continuity
Q.
Is the check result normal?
Go to Step 14.
NO (Not normal at the terminal No. 18 or 6) : Go to Step 10.
NO (Not normal at the terminal No. 34 or 22) : Go to Step 11.
NO (Not normal at the terminal No. 19 or 31) : Go to Step 12.
NO (Not normal at the terminal No. 33 or 20) : Go to Step 13.
The short circuit may be present in the front wheel speed sensor <RH> circuit.
Repair the wiring harness between A-14 ASC-ECU connector terminal No.6 and A-21 front wheel
speed sensor <RH> connector terminal No.1, and between A-14 ASC-ECU connector
terminal No.18 and A-21 front wheel speed sensor <RH> connector terminal No.2.
The short circuit may be present in the front wheel speed sensor <LH> circuit.
Repair the wiring harness between A-14 ASC-ECU connector terminal No.22 and A-18 front wheel
speed sensor <LH> connector terminal No.1, and between A-14 ASC-ECU connector
terminal No.34 and A-18 front wheel speed sensor <LH> connector terminal No.2.
The short circuit may be present in the rear wheel speed sensor <RH> circuit.
Repair the wiring harness between A-14 ASC-ECU connector terminal No.19 and C-27 rear wheel
speed sensor <RH> connector terminal No.2, and between A-14 ASC-ECU connector
terminal No.31 and C-27 rear wheel speed sensor <RH> connector terminal No.1.
The short circuit may be present in the rear wheel speed sensor <LH> circuit.
Repair the wiring harness between A-14 ASC-ECU connector terminal No.20 and C-15 rear wheel
speed sensor <LH> connector terminal No.1, and between A-14 ASC-ECU connector
terminal No.33 and C-15 rear wheel speed sensor <LH> connector terminal No.2.
Repair the defective connector.
STEP 14. Voltage measurement at the A-14 ASC-ECU connector
(1)Disconnect the ASC-ECU connector, connect special tool ABS check harness (MB992335)
to the ASC-ECU-side connector and harness-side connector, and then measure the voltage at the
special tool connector side. (2)Turn the electric motor switch to the "ON" position. (3)Measure the voltage between the front wheel speed sensor circuit power supply terminal
and the body earth and between the front wheel speed sensor circuit signal terminal and the
body earth.
Diagnosis code No.
Check terminal
Power supply terminal
Signal terminal
C1201
No. 18
No. 6
C1206
No. 34
No. 22
C1211
No. 19
No. 31
C1216
No. 33
No. 20
OK:
Approximately system voltage <Power supply terminal> 0.4 - 1.3V or less <Signal terminal>
Q.
Is the check result normal?
Go to Step 23.
NO (Not normal at the terminal No. 18 or 6) : Go to Step 15.
NO (Not normal at the terminal No. 34 or 22) : Go to Step 17.
NO (Not normal at the terminal No. 19 or 31) : Go to Step 19.
NO (Not normal at the terminal No. 33 or 20) : Go to Step 21.
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Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table 
).
On completion, go to Step 2.)
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: Go to Step 10.)
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