C1206

DTC C1206: FL wheel SPD. SNSR. invalid signal

TCL/ASC Sensor Circuit

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 ABS rotor generates a voltage pulse as it moves across the pickup field of each ABS sensor.
^ The amount of voltage generated at each wheel is determined by the clearance between the ABS rotor teeth and the ABS 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.

ABS DTC SET CONDITIONS
The TCL/ASC-ECU monitors the signals from each ABS 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 ABS sensor signals

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

Current trouble
^ Malfunction of the ABS sensor or ABS 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 ABS 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 codes 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. C1205
NO: Go to Step 4.

STEP 4. Check the installation condition of the ABS sensors.
For the ABS sensor, which the DTC code indicates, check whether the sensor or its mounting bolts are loosened.
^ DTC C1206 is set: Front left ABS sensor

Q: Is the ABS sensor installed correctly?
YES: Go to Step 5.
NO: Reinstall the ABS sensor correctly. Then go to Step 13.

STEP 5. Check the ABS sensor after it is removed from the vehicle.
Check the ABS sensor, which the DTC code indicates.
^ DTC C1206 is set: Front left ABS sensor

Q: Is the ABS sensor in good condition?
YES: Go to Step 6.
NO: Replace the ABS sensor. Then go to Step 13.

STEP 6. Check the wheel bearing for looseness.

NOTE: If the wheel bearing is loose, the gap between the ABS sensor and rotor may become excessive. Check the wheel bearing, which DTC code 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 13.

STEP 7. Check the ABS rotor.
Check the ABS rotor, which DTC code indicates, for foreign material or deformation.
^ DTC C1206 is set: Front left ABS sensor

Q: Is the ABS rotor in good condition?
YES: Go to Step 8.
NO: (front bearing end play is not within the standard value) If the ABS rotor is contaminated with foreign material, clean it. If the driveshaft is deformed, replace it. Then go to Step 13.

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 ABS 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 1 V or less?
YES: Go to Step 9.
NO: (When the voltage between terminal 45 or 46 and body ground measures more than 1 V) Go to Step 11.

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 ABS sensor circuit and body ground. OK if there is no continuity.
^ DTC C1206 is set: Between signal terminal 45 and body ground, and between ground terminal 46 and body ground

Q: Does continuity exist?
YES: (Continuity exists between terminal 45 or terminal 46 and body ground) Go to Step 11.
NO: Go to Step 10.

STEP 10. Measure the resistance at TCL/ASC-ECU connector A38.

(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 ABS 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 12.
NO: (When resistance between terminals 45 and 46 is not within the standard value) Go to Step 11.

STEP 11. Check TCL/ASC-ECU connector A-38 and ABS 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 ABS sensor [front: LH] connector A-06 damaged?
YES: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. Then go to Step 13.
NO: Open or short circuit may be present in the front right ABS sensor circuit. Repair the wiring harness between TCL/ASC-ECU connector A-38 (terminals 45 and 46) and front left ABS sensor A-06 (terminals 1 and 2). Then go to Step 13.

STEP 12. 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 13.
NO: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points -How to Cope with Intermittent Malfunction.

STEP 13. Recheck for diagnostic trouble code.