C1044

DTC C1044: Abnormality in periodical signal for RR wheel speed sensor

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
^ The wheel speed sensor is a type of 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 ABS-ECU. ABS-ECU uses the frequency of the pulse signals to determine the wheel speed.

DTC SET CONDITIONS
ABS-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, ABS-ECU will set the relevant diagnostic trouble code.

PROBABLE CAUSES
^ Wheel bearing malfunction
^ Deformation of the magnetic encoder for wheel speed detection
^ Missing teeth 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

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
^ MB991974: ABS check harness

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. Diagnostic trouble code recheck after resetting CAN bus lines
Q: Is DTC C1044 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 [RR] for looseness.

Q: Is the check result normal?
YES: Go to Step 4.
NO: Replace the rear wheel hub assembly.

STEP 4. Check 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 (Presence 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 rear hub assembly.
NO (Deformation): Replace the rear wheel hub assembly.

STEP 5. Check whether the diagnostic trouble code 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 ABS-ECU.
NO: Intermittent malfunction.