C1048
DTC C1048 RL wheel speed sensor control phase time exceeded
CAUTION
^ 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 (Refer to Diagnostic trouble code diagnosis Diagnostic Trouble Code Descriptions).
^ 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
^ 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
This DTC is set if any malfunction below is found:
^ When the brake fluid pressure is decreased for a long time.
^ When the brake fluid pressure is held for a long time.
NOTE: ASC controls the vehicle based on the wheel speed signal. When the brake fluid pressure is decreased or held for an abnormally long time, the wheel speed sensor signal may have a problem.
PROBABLE CAUSES
^ Damaged wiring harness and connectors
^ External noise interference
^ Malfunction of wheel speed sensor
^ ASC-ECU malfunction
^ Excessive gap between the wheel speed sensor and the wheel speed detection encoder
^ Adhesion of foreign materials on the wheel speed sensor
^ Adhesion of foreign materials on the wheel speed detection encoder
^ Wheel bearing malfunction
^ Improper installation of the wheel speed sensor
^ Deformation of the wheel speed detection encoder
^ Disturbance of magnetization pattern for wheel speed detection encoder
^ Missing teeth of the wheel speed detection encoder
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.
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 (Refer to Diagnosis - CAN Bus Diagnostic Table CAN Bus Diagnostics Table). On completion, go to Step 2.
STEP 2. DTC recheck after resetting CAN bus lines
Q: Is DTC C1048 set?
YES: Go to Step 3.
NO: The procedure is complete.
STEP 3. Using scan tool MB991958, check the DTC
Check that the DTC C1020, C1027, C102A, or C1043 is also set.
Q: Is the DTC C1020, C1027, C102A, or C1043 also set?
YES: Carry out the diagnosis for the relevant DTC, and then go to Step 5.
NO: Go to Step 4.
STEP 4. Using scan tool MB991958, check the data list
Check the following service data (Refer to Scan Tool Testing and Procedures).
^ Item No.03: RL wheel speed sensor
Q: Is the check result normal?
YES: Go to Step 14.
NO: Go to Step 5.
STEP 5. Connector check: A-51 ASC-ECU connector, C-39 intermediate connector, D-15 intermediate connector, F-21 wheel speed sensor [RL] connector
Q: Is the check result normal?
YES: Go to Step 6.
NO: Repair the defective connector. Then go to Step 15.
STEP 6. Voltage measurement at the A-51 ASC-ECU connector
1. Disconnect the ASC-ECU connector, connect special tool ASC check harness (MB991997) to the harness-side connector, and then measure the voltage at the special tool connector side.
NOTE: Do not connect the special tool ASC check harness (MB991997) to ASC-ECU.
2. Turn the ignition switch to the ON position.
3. Measure the voltage between the wheel speed sensor power supply terminal (signal terminal) No.36 and the body ground, and between the wheel speed sensor ground terminal No.37 and the body ground.
OK: 1 volt or less
Q: Is the check result normal?
YES: Go to Step 7.
NO (Not normal at the terminal No.36 or No.37): Go to Step 9.
STEP 7. Resistance measurement at A-51 ASC-ECU connector
1. Disconnect the ASC-ECU connector, connect special tool ASC check harness (MB991997) to the harness-side connector, and then measure the resistance at the special tool connector side.
NOTE: Do not connect the special tool ASC check harness (MB991997) to ASC-ECU.
2. Measure the resistance between the wheel speed sensor power supply terminal No.36 and the body ground, and between the wheel speed sensor ground terminal No.37 and the body ground.
OK: No continuity
Q: Is the check result normal?
YES: Go to Step 8.
NO (Not normal at the terminal No.36 or No.37): Go to Step 9.
STEP 8. Voltage measurement at the A-51 ASC-ECU connector
1. Disconnect the ASC-ECU connector, connect special tool ASC check harness (MB991997) to the ASC-ECU-side connector and harness-side connector, and then measure the voltage at the special tool connector side.
2. Turn the ignition switch to the ON position.
3. Measure the voltage between the wheel speed sensor power supply terminal (signal terminal) No.36 and body ground, and between the ground terminal No.37 and body ground.
OK:
Terminal No.36 and body ground: Battery positive voltage
Terminal No.37 and body ground: 1 volt or less
Q: Is the check result normal?
YES: Go to Step 9.
NO: Go to Step 14.
STEP 9. Check for wheel speed sensor as a single unit
Refer to Service and Repair.
Q: Is the check result normal?
YES: Go to Step 10.
NO: Replace the wheel speed sensor [RL]. Then go to Step 15.
STEP 10. Wiring harness check between A-51 ASC-ECU connector terminal No.36 and F-21 wheel speed sensor [RL] connector terminal No.1, and between A-51 ASC-ECU connector terminal No.37 and F-21 wheel speed sensor [RL] connector terminal No.2.
^ Check for open or short circuit in wheel speed sensor [RL] circuit
Q: Is the check result normal?
YES: Go to Step 11.
NO: Repair the wiring harness. Then go to Step 15.
STEP 11. Check for wheel speed sensor installation
Check how the wheel speed sensor [RL] is installed (Disconnection of wheel speed sensor, loose mounting bolt, etc.).
Q: Is the check result normal?
YES: Go to Step 12.
NO: Reinstall the wheel speed sensor [RL] correctly. Then go to Step 15.
STEP 12. 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 Rear wheel hub assembly [RL (FWD)].
^ Check the wheel bearing [RL (AWD)] for looseness.
Q: Is the check result normal?
YES: Go to Step 13.
NO (FWD): Replace the rear wheel hub assembly. Then go to Step 15.
NO (AWD): Replace the wheel bearing. Then go to Step 15.
STEP 13. 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 14.
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.
NO [Deformation (FWD)]: Replace the rear wheel hub assembly. Then go to Step 15.
NO [Deformation (AWD)]: Replace the wheel bearing. Then go to Step 15.
STEP 14. 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 C1048 set?
YES: Replace the hydraulic unit (ASC-ECU). Then go to Step 15.
NO: The procedure is complete.
STEP 15. 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 C1048 set?
YES: Return to Step 1.
NO: The procedure is complete.