TCS or ASC

DTC C1206: FL wheel SPD. SNSR. invalid signal

CAUTION
If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set.
Prior to this diagnosis, diagnose the CAN bus lines.

CIRCUIT OPERATION
^ A toothed rotor generates a voltage pulse as it moves across the pickup field of each wheel speed sensor.
^ The amount of voltage generated at each wheel is determined by the clearance between the rotor teeth and the wheel speed sensor, and by the speed of rotation.
^ Sends alternating current signals at frequencies which are proportional to the rotation speeds of each wheel to the TCL/ASC electronic control unit (TCL/ASC-ECU).
^ The ABS hydraulic unit modulates the amount of braking force individually applied to each wheel cylinder.

DTC SET CONDITIONS
The TCL/ASC-ECU monitors the signals from each wheel speed sensor while the vehicle is being driven. If any faults below are found in these sensor signals, the ECU will set the relevant diagnostic trouble code.
^ Missing sensor signal
^ Sensor signal, which will not be created under normal operation
^ Significant difference among the wheel speed sensor signals

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THESE DTCS ARE TO SET ARE:)

Current trouble
^ Malfunction of the wheel speed sensor or rotor
^ Damaged wiring harness or connector
^ Malfunction of the hydraulic unit (integrated with TCL/ASC-ECU)

Past trouble
^ Carry out diagnosis with particular emphasis on connector(s) or wiring harness in wheel speed sensor circuit. For diagnosis procedures, refer to "How to cope with 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
^ MB991997: ASC Check Harness

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

CAUTION

To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1) Connect scan tool MB991958 to the data link connector.
2) Turn the ignition switch to the "ON" position.
3) Diagnose the CAN bus line.
4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?
YES: Go to Step 3.
NO: Repair the CAN bus line. Then go to Step 2.

STEP 2. Recheck for diagnostic trouble code.

CAUTION

To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1) Turn the ignition switch to the "ON" position.
2) Erase the DTC.
3) Turn the ignition switch to the "LOCK" (OFF) position.
4) Turn the ignition switch to the "ON" position.
5) Check if the DTC is set.
6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1206 set?
YES: Go to Step 3.
NO: The procedure is complete.

STEP 3. Using scan tool MB991958, read the diagnostic trouble code.

CAUTION

To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958, Use scan tool MB991958 to check whether DTC C1205 have been set simultaneously.

1) Connect scan tool MB991958 to the data link connector.
2) Turn the ignition switch to the "ON" position.
3) Check whether DTC C1205 have been set.
4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1205 set?
YES: Carry out diagnosis relevant to DTC C1205.
NO: Go to Step 4.

STEP 4. Check the installation condition of the wheel speed sensors. For the wheel speed sensor, which the DTC indicates, check whether the sensor or its mounting bolts are loosened.
^ DTC C1206 is set: Front left wheel speed sensor
Q: Is the wheel speed sensor installed correctly?
YES: Go to Step 5.
NO: Reinstall the wheel speed sensor correctly. Then go to Step 14.

STEP 5. Check the wheel speed sensor after it is removed from the vehicle.
Check the wheel speed sensor, which the DTC indicates.
^ DTC C1206 is set: Front left wheel speed sensor
Q: Is the wheel speed sensor in good condition?
YES: Go to Step 6.
NO: Replace the wheel speed sensor. Then go to Step 14.

STEP 6. Check the wheel bearing for looseness.

NOTE: If the wheel bearing is loose, the gap between the wheel speed sensor and rotor may become excessive. Check the wheel bearing, which DTC indicates, for looseness.

^ DTC C1206 is set: Check the front left wheel bearing.
Q: Is the wheel bearing end play within the standard value?
YES: Go to Step 7.
NO (front bearing end play is not within the standard value): Replace the front hub assembly. Then go to Step 14.

STEP 7. Check the rotor.
Check the rotor, which DTC indicates, for foreign material or deformation.
^ DTC C1206 is set: Front left wheel speed sensor
Q: Is the rotor in good condition?
YES: Go to Step 8.
NO (front bearing end play is not within the standard value): If the rotor is contaminated with foreign material, clean it. If the driveshaft is deformed, replace it. Then go to Step 14.

STEP 8. Measure the voltage at TCL/ASC-ECU connector A-38.

1) Disconnect the connector A-38, and connect special tool MB991997 to the wiring harness-side connector.

NOTE: Do not connect special tool MB991997 to the [TCL/ASC-ECU]

2) Turn the ignition switch to the "ON" position.
3) Measure the voltage between the relevant signal and ground terminals in the wheel speed sensor circuit and body ground. It should be less than 1V.
^ DTC C1206 is set: Between signal terminal 45 and body ground, and between ground terminal 46 and body ground
Q: Does the voltage measure 1V or less?
YES: Go to Step 9.
NO (When the voltage between terminal 45 or 46 - and body ground measures more than 1V): Go to Step 12.

STEP 9. Measure the resistance at TCL/ASC-ECU connector A-38.

1) Disconnect the connector A-38, and connect special tool MB991997 to the wiring harness-side connector.

NOTE: Do not connect special tool MB991997 to the [TCL/ASC-ECU]

2) Measure the resistance between the relevant signal and ground terminals in the wheel speed sensor circuit.
^ DTC C1206 is set: Between signal terminal 45 and ground terminal 46
Standard Value: 1.24 - 1.64 k ohms
Q: Is the resistance between terminals 45 and 46 within the standard value?
YES (When resistances between all terminals are within the standard value): Go to Step 13.
NO (When resistance between terminals 45 and 46 is not within the standard value): Go to Step 11.

STEP 11. Inspect the wheel speed sensor.
Check the front left wheel speed sensor relevant to the DTC. For the applicable inspection procedure.
Q: Is the wheel speed sensor damaged?
YES: Replace the wheel speed sensor.

STEP 12. Check TCL/ASC-ECU connector A-38 and wheel speed sensor [front: LH] connector A-06 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are TCL/ASC-ECU connector A-38 and wheel speed sensor [front: LH] connector A-06 damaged?
YES: Repair or replace the damaged component(s). Then go to Step 14.
NO: Open or short circuit may be present in the front right wheel speed sensor circuit. Repair the wiring harness between TCL/ASC-ECU connector A-38 (terminals 45 and 46) and front left wheel speed sensor A-06 (terminals 1 and 2). Then go to Step 14.

STEP 13. Recheck for diagnostic trouble code.

Check again if the DTC is set.
1) Turn the ignition switch to the "ON" position.
2) Erase the DTC
3) Turn the ignition switch to the "LOCK" (OFF) position.
4) Turn the ignition switch to the "ON" position.
5) Check if the DTC is set.
6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1206 set?
YES: Replace the hydraulic unit (integrated with TCL/ASC-ECU). Then go to Step 14.
NO: It can be assumed that this malfunction is intermittent.

STEP 14. Recheck for diagnostic trouble code.