C1044
DTC C1044: Abnormality in periodical signal for RR wheel speed sensorCAUTION:
^ 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.
^ Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve.
DTC SET CONDITIONS
^ Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
^ The pulse signals generated by the wheel speed detecting section 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 abnormality is detected in the sensor signals, ASC-ECU sets the relevant diagnostic trouble code.
PROBABLE CAUSES
^ Wheel bearing malfunction
^ Deformation of the magnetic encoder for wheel speed detection
^ Adhesion of foreign materials on the magnetic encoder for wheel speed detection
^ ABS-ECU malfunction
^ Disturbance of magnetization pattern for magnetic encoder for wheel speed detection
^ Missing teeth of the magnetic encoder for wheel speed detection
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 lines.
Using scan tool MB991958, diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. (Refer to Troubleshooting Can Bus Diagnostics Table.) After repairing the CAN bus line, go to Step 2.
STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C1044 set?
YES: Go to Step 3.
NO: This diagnosis is complete.
STEP 3. Wheel bearing looseness check
NOTE: Wheel bearing looseness may increase the gap between the wheel speed sensor and the wheel speed detection magnet encoder. Check the wheel bearing [RR] for looseness. (Refer to On-vehicle Service Testing and Inspection.)
Q: Is the check result normal?
YES: Go to Step 4.
NO: Replace the rear wheel hub assembly.
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): Clean the encoder so as not to disturb the magnetization pattern on the encoder while taking care of the magnet, magnetic substance, and magnetic attraction.
NO (Deformation): Replace the rear wheel hub assembly.
STEP 5. Check whether the DTC is reset.
1) Erase the diagnostic trouble code.
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 C1044 set?
YES: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 6.
NO: Intermittent malfunction.
STEP 6. Check whether the DTC is reset.
1) Erase the diagnostic trouble code.
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 C1044 set?
YES: Return to Step 1.
NO: This diagnosis is complete.