C1048
DTC C1048: RL wheel speed sensor control phase time exceeded
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.
^ 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.
CIRCUIT 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 diagnostic trouble code is set if any malfunction below is detected.
^ 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
^ ABS-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.
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 C1048 set?
YES: Go to Step 3.
NO: This diagnosis is complete.
STEP 3. Scan tool diagnostic trouble code
Check that DTC No. C1020, C1027, C102A, and C1043 are simultaneously set.
Q: Are DTC C1020, C1027, C102A and C1043 also set?
YES: Carry out the diagnosis for the diagnostic trouble codes that are set, and then go to Step 5.
NO: Go to Step 4.
STEP 4. Scan tool service data
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 16.
NO: Go to Step 5.
STEP 5. Voltage measurement at A-05 ASC-ECU connector
1) Disconnect the ASC-ECU connector, connect the special tool ASC check harness (MB991997) to the wiring harness-side connector, and then measure at the special tool connector side.
NOTE: Do not connect the special tool 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 as well as between the ground terminal No. 37 and the body ground.
OK: 1 volt or less
Q: Is the check result normal?
YES: Go to Step 6.
NO (Not normal at terminal No. 34 or 33): Go to Step 7.
STEP 6. Resistance measurement at A-05 ASC-ECU connector
1) Disconnect the ASC-ECU connector, connect the special tool ASC check harness (MB991997) to the wiring harness-side connector, and then measure at the special tool connector side.
NOTE: Do not connect the special tool to ASC-ECU.
2) Measure the resistance between the wheel speed sensor circuit power supply terminal (signal terminal) No. 36 and the body ground as well as between the ground terminal No. 37 and the body ground.
OK: No continuity
Q: Is the check result normal?
YES: Go to Step 9.
NO (Not normal at the terminal No. 36 or 37): Go to Step 7.
STEP 7. Connector check: A-05 ASC-ECU connector, C-45 intermediate connector, D-18 wheel speed sensor [RL] connector
Q: Is the check result normal?
YES: Go to Step 8.
NO: Repair the defective connector. Then go to Step 17.
STEP 8. Wiring harness check between A-05 ASC-ECU connector terminal No. 36 and D-18 wheel speed sensor [RL] connector terminal No. 1, and between A-05 ASC-ECU connector terminal No. 37 and D-18 wheel speed sensor [RL] connector terminal No. 2
^ Short circuit check of wheel speed sensor [RL] circuit
Q: Is the check result normal?
YES: Replace the wheel speed sensor [RL]. Then go to Step 17.
NO: Repair the wiring harness. Then go to Step 17.
STEP 9. Voltage measurement at A-05 ASC-ECU connector
1) Disconnect the ASC-ECU connector, connect the special tool ASC check harness (MB991997) to the ASC-ECU-side connector and the wiring harness-side connector, and then measure at the special tool connector side.
2) Turn the ignition switch to the ON position.
3) Measure the voltage between the wheel speed sensor circuit power supply terminal (signal terminal) No. 36 and the body ground.
OK: Battery positive voltage
Q: Is the check result normal?
YES: Go to Step 10.
NO: Go to Step 12.
STEP 10. Wiring harness check between A-05 ASC-ECU connector terminal No. 36 and D-18 wheel speed sensor [RL] connector terminal No. 1, and between A-05 ASC-ECU connector terminal No. 37 and D-18 wheel speed sensor [RL] connector terminal No. 2
^ Open circuit check of 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 17.
STEP 11. Check of wheel speed sensor as a single unit
Q: Is the check result normal?
YES: Go to Step 13.
NO: Replace the wheel speed sensor [RL]. Then go to Step 17.
STEP 12. Connector check: A-05 ASC-ECU connector, C-45 intermediate connector, D-18 wheel speed sensor [RL] connector
Q: Is the check result normal?
YES: Go to Step 16.
NO: Repair the defective connector. Then go to Step 17.
STEP 13. Check of wheel speed sensor installation status
Check the installation status of wheel speed sensor [RL] (disconnection of wheel speed sensor, looseness of mounting bolt, etc.).
Q: Is the check result normal?
YES: Go to Step 14.
NO: Reinstall the wheel speed sensor [RL] correctly. Then go to Step 17.
STEP 14. 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 [RL] for looseness. (Refer to On-vehicle Service Testing and Inspection.)
Q: Is the check result normal?
YES: Go to Step 15.
NO: Replace the rear wheel hub assembly.
STEP 15. 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 16.
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 16. Check whether the DTC is reset.
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 (incorporates in ASC-ECU). Then go to Step 17.
NO: Intermittent malfunction.
STEP 17. Check whether the DTC is reset.
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: This diagnosis is complete.