Code No. C1222:
Wheel SPD. SNSR. power circuit
Code No. C1225: Deviation between wheel speed
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- 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
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- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
- When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out
the calibration of the G and yaw rate sensor and the steering wheel sensor (Refer to and ).
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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 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
The ASC-ECU monitors the signals from each wheel speed sensor. If any faults below is
found in these sensor signals, the ECU will set the relevant diagnosis code. When the abnormal
wheel is identified, diagnosis code No. C1014, C101F, C102A, or C1035 is set.
- Missing sensor signal.
- Sensor signal, which will not be created under normal operation.
- Unfeasible difference among the wheel speed sensor signals.
- When the ABS/ASC control is being activated for one minute or more.
PROBABLE CAUSES
Current trouble
- Improper installation of the wheel speed sensor
- Malfunction of the wheel speed sensor
- Wheel bearing malfunction
- Excessive gap between the wheel speed sensor and the wheel speed detection magnetic
encoder
- Adhesion of foreign materials on the wheel speed detection magnetic encoder
- Deformation of the wheel speed detection magnetic encoder
- Damaged harness wires and connectors
- Malfunction of ASC-ECU
Past trouble
- The following conditions may occur.
- Either of the right or left wheel is turning, or either of the front or rear wheel
are turning.
- Unstable vehicle attitude.
- External noise interference.
- The vehicle is driven on snowy or rough road.
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STEP 1. M.U.T.-III CAN bus diagnosis.
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Use the M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 3.
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 Repair the CAN bus line (Refer to GROUP 54C, Troubleshooting ).
On completion, go to Step 2.
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STEP 2. Diagnosis code recheck after resetting CAN bus lines.
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Q.
Is the relevant diagnosis code No. CC1222 or C1225 set?
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Go to Step 3.
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This diagnosis is complete.
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STEP 3. Check whether the wheel speed sensors are installed properly.
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Check the mounting status of wheel speed sensors (sensor dislocation, mounting bolt loosening,
etc.) for all wheels.
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Q.
Is the check result normal?
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Go to Step 4.
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Install the wheel speed sensor properly. Then go to Step 16.
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STEP 4. Check for wheel speed sensor as a single unit.
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Q.
Is the check result normal?
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Go to Step 5.
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Replace the wheel speed sensor. Then go to Step 16.
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STEP 5. Check for wheel bearing looseness.
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The wheel bearing looseness is suspected to be the cause of excessive gap between the
wheel speed sensor and encoder. Therefore, check the wheel bearing looseness of each wheel.
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Q.
Is the check result normal?
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Go to Step 6.
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Replace the wheel bearing. Then go to Step 16.
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STEP 6. Check of wheel speed detection magnetic encoder are installed
properly.
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Check the wheel speed detection magnetic encoder for adhesion of foreign materials or
deformation.
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Q.
Is the check result normal?
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Go to Step 7.
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NO <when the relevant wheel is front> : 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.
If deformation is found, replace the wheel bearing. Then go to Step 16.
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NO <when the relevant wheel is rear> : 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.
If deformation is found, replace the pulse rotor. Then go to Step 16.
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STEP 7. Measure the voltage at the ASC-ECU connector.
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(1)Connector check: ASC-ECU connector and wheel speed sensor connectors.
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(2)Disconnect the connector, and measure at the wiring harness side.
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(3)Ignition switch: "ON".
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(4)Measure the voltage between the power supply terminal as well as signal terminal
of wheel speed sensor circuit and the body earth.
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Position of wheel speed sensors
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Checking terminal
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Power supply terminal
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Signal terminal
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Right front wheel
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FR+
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FR-
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Left front wheel
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FL+
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FL-
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Right rear wheel
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RR+
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RR-
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Left rear wheel
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RL+
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RL-
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OK: 1 V or less
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Q.
Is the check result normal?
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Go to Step 8.
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NO (FR+ or FR- NG) : Go to Step 10.
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NO (FL+ or FL- NG) : Go to Step 11.
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NO (RR+ or RR- NG) : Go to Step 12.
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NO (RL+ or RL- NG) : Go to Step 13.
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STEP 8. Measure the resistance at the ASC-ECU connector.
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Measure the resistance between the power supply terminal as well as signal terminal
of each wheel speed sensor circuit and body earth.
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Position of wheel speed sensors
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Checking terminal
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Power supply terminal
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Signal terminal
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Right front wheel
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FR+
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FR-
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Left front wheel
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FL+
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FL-
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Right rear wheel
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RR+
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RR-
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Left rear wheel
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RL+
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RL-
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OK: No continuity
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Q.
Is the check result normal?
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Go to Step 9.
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NO (FR+ or FR- NG) : Go to Step 10.
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NO (FL+ or FL- NG) : Go to Step 11.
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NO (RR+ or RR- NG) : Go to Step 12.
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NO (RL+ or RL- NG) : Go to Step 13.
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STEP 9. Measure the voltage at the ASC-ECU connector.
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(1)Measure with the connector(s) connected.
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(2)Ignition switch: "ON".
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(3)Measure the voltage between the power supply terminal as well as signal terminal
of each wheel speed sensor circuit and body earth.
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Position of wheel speed sensors
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Checking terminal
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Power supply terminal
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Signal terminal
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Right front wheel
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FR+
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FR-
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Left front wheel
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FL+
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FL-
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Right rear wheel
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RR+
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RR-
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Left rear wheel
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RL+
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RL-
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OK:
Power supply terminal: Approx. system voltage
Signal terminal: approximately 0.4 to 1.3 V
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Q.
Is the check result normal?
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Go to Step 14.
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NO (FR+ or FR- NG) : Go to Step 10.
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NO (FL+ or FL- NG) : Go to Step 11.
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NO (RR+ or RR- NG) : Go to Step 12.
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NO (RL+ or RL- NG) : Go to Step 13.
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STEP 10. Check the wiring harness wires between the ASC-ECU connector
FR (+) or FR (-) terminal and the front wheel speed sensor (RH) connector
terminal.
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Check the front wheel speed sensor (RH) circuit for short and open.
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Q.
Is the check result normal?
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Go to Step 14.
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Repair the connector(s) and wiring harness. Then go to Step 16.
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STEP 11. Check the wiring harness wires between the ASC-ECU connector
FL (+) or FL (-) terminal and the front wheel speed sensor (LH) connector
terminal.
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Check the front wheel speed sensor (LH) circuit for short and open.
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Q.
Is the check result normal?
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Go to Step 14.
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Repair the connector(s) and wiring harness. Then go to Step 16.
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STEP 12. Check the wiring harness wires between the ASC-ECU connector
RR (+) or RR (-) terminal and the rear wheel speed sensor (RH) connector terminal.
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Check the rear wheel speed sensor (RH) circuit for short and open.
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Q.
Is the check result normal?
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Go to Step 14.
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Repair the connector(s) and wiring harness. Then go to Step 16.
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STEP 13. Check the wiring harness wires between ASC-ECU connector
RL (+) or RL (-) terminal and the rear wheel speed sensor (LH) connector terminal.
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Check the rear wheel speed sensor (LH) circuit for short and open.
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Q.
Is the check result normal?
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Go to Step 14.
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Repair the connector(s) and wiring harness. Then go to Step 16.
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STEP 14. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "ON" position.
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(2)Turn the ignition switch to the "LOCK" (OFF) position.
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(3)Drive the vehicle at 20 km/h or more.
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Q.
Is diagnosis code No. C1222 or C1225 set?
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Replace the wheel speed sensor. Then go to Step 15.
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The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to Cope with Intermittent Malfunction).
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STEP 15. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "ON" position.
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(2)Turn the ignition switch to the "LOCK" (OFF) position.
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(3)Drive the vehicle at 20 km/h or more.
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Q.
Is diagnosis code No. C1222 or C1225 set?
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Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to ). Then
go to Step 16.
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The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to Cope with Intermittent Malfunction).
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STEP 16. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "ON" position.
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(2)Turn the ignition switch to the "LOCK" (OFF) position.
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(3)Drive the vehicle at 20 km/h or more.
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Q.
Is diagnosis code No. C1222 or C1225 set?
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Return to Step 3.
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This diagnosis is complete.
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