ASC
DTC C1042 Abnormality in periodical signal for FR wheel speed sensorCAUTION
^ If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines.
^ 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 steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor.
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.
DTC SET CONDITIONS
ASC-ECU monitors the signals from each wheel speed sensor while the vehicle is being driven. If any periodical drop is found in these sensor signals, ASC-ECU will set the relevant DTC.
PROBABLE CAUSES
^ Wheel bearing malfunction
^ Deformation of the wheel speed detection encoder
^ Missing teeth of the wheel speed detection encoder
^ Adhesion of foreign materials on the wheel speed detection encoder
^ ASC-ECU malfunction
^ The number of poles on the Magnetic encoder for wheel speed detection (N-pole and S-pole) is changed
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
STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. On completion, go to Step 2.
STEP 2. DTC recheck after resetting CAN bus lines
Q: Is DTC C1042 set?
YES: Go to Step 3.
NO: The procedure is complete.
STEP 3. 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 [FR] for looseness.
Q: Is the check result normal?
YES: Go to Step 4.
NO: Replace the wheel bearing.
STEP 4. Check of wheel speed detection encoder
Check the encoder for adhesion of foreign materials or deformation.
Q: Is the check result normal?
YES: Go to Step 5.
NO (Adhesion of foreign materials): 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 wheel bearing.
NO (Deformation): Replace the wheel bearing.
STEP 5. Check whether the DTC is reset.
1) Erase the DTC.
2) Drive the vehicle at 12 mph (20 km/h) or more.
NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12 mph (20 km/h) or higher.
Q: Is DTC C1042 set?
YES: Replace the hydraulic unit (ASC-ECU). Then go to Step 6.
NO: Intermittent malfunction.
STEP 6. Check whether the DTC is reset.
1) Erase the DTC.
2) Drive the vehicle at 12 mph (20 km/h) or more.
NOTE: The ABS warning light does not turn OFF in some cases unless the vehicle runs at 12 mph (20 km/h) or higher.
Q: Is DTC C1042 set?
YES: Return to Step 1.
NO: The procedure is complete.