Code No. C1048 RL wheel speed sensor control phase time exceeded
















caution If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C, Trouble code diagnosis ).

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 ABS-ECU. ABS-ECU uses the frequency of the pulse signals to determine the wheel speed.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code 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.

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 magnetisation pattern for wheel speed detection encoder
  • Missing teeth of the wheel speed detection encoder

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnosis table ). On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

Q. Is the diagnosis code No.C1048 set?
Go to Step 3.
This diagnosis is complete.

STEP 3. M.U.T.-III diagnosis code
Check that the diagnosis codes No. C1020, C1027, C102A, and C1043 are also set.

Q. Are the diagnosis codes No. C1020, C1027, C102A, and C1043 also set?
Carry out the diagnosis for the relevant diagnosis codes, and then go to Step 5.
Go to Step 4.

STEP 4. M.U.T.-III data list
Check the following service data (Refer to ).

  • Item No.01: FL wheel speed sensor
  • Item No.02: FR wheel speed sensor
  • Item No.03: RL wheel speed sensor
  • Item No.04: RR wheel speed sensor

Q. Is the check result normal?
Go to Step 16.
Go to Step 5.

STEP 5. Voltage measurement at the A-04 ABS-ECU connector

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and then measure the voltage at the special tool connector side.
note Do not connect the special tool ABS check harness (MB991974) to ABS-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.24 and the body earth, and between the wheel speed sensor earth terminal No.25 and the body earth.
OK: 1 volt or less

Q. Is the check result normal?

Go to Step 6.

NO (Not normal at the terminal No.24 or 25) : Go to Step 7.

STEP 6. Resistance measurement at A-04 ABS-ECU connector

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the harness-side connector, and then measure the resistance at the special tool connector side.
note Do not connect the special tool ABS check harness (MB991974) to ABS-ECU.
(2)Resistance between the wheel speed sensor power supply terminal (signal terminal) No.24 and body earth, and between the earth terminal No.25 and body earth.
OK: No continuity

Q. Is the check result normal?

Go to Step 9.

NO (Not normal at the terminal No.24 or 25) : Go to Step 7.

STEP 7. Connector check: A-04 ABS-ECU connector, C-31 intermediate connector, D-17 intermediate connector, F-24 wheel speed sensor <RL> connector

Q. Is the check result normal?
Go to Step 8.
Repair the defective connector. Then go to Step 17.

STEP 8. Wiring harness check between A-04 ABS-ECU connector terminal No.24 and F-24 wheel speed sensor <RL> connector terminal No.1, and between A-04 ABS-ECU connector terminal No.25 and F-24 wheel speed sensor <RL> connector terminal No.2

  • Check for short circuit in wheel speed sensor <RL> circuit

Q. Is the check result normal?
Replace the wheel speed sensor <RL> (Refer to ). Then go to Step 17.
Repair the wiring harness. Then go to Step 17.

STEP 9. Voltage measurement at the A-04 ABS-ECU connector

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) to the ABS-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 circuit power supply terminal (signal terminal) No.24 and the body earth.
OK: Approximately battery voltage

Q. Is the check result normal?

Go to Step 10.

Go to Step 12.

STEP 10. Wiring harness check between A-04 ABS-ECU connector terminal No.24 and F-24 wheel speed sensor <RL> connector terminal No.1, and between A-04 ABS-ECU connector terminal No.25 and F-24 wheel speed sensor <RL> connector terminal No.2.

  • Check for open circuit in wheel speed sensor <RL> circuit

Q. Is the check result normal?
Go to Step 11.
Repair the wiring harness. Then go to Step 17.

STEP 11. Check for wheel speed sensor as a single unit
Refer to .

Q. Is the check result normal?
Go to Step 13.
Replace the wheel speed sensor <RL> (Refer to ). Then go to Step 17.

STEP 12. Connector check: A-04 ABS-ECU connector, C-31 intermediate connector, D-17 intermediate connector, F-24 wheel speed sensor <RL> connector

Q. Is the check result normal?
Go to Step 16.
Repair the defective connector. Then go to Step 17.

STEP 13. 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?
Go to Step 14.
Reinstall the wheel speed sensor <RL> correctly (Refer to ). Then go to Step 17.

STEP 14. 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 <RL> for looseness (Refer to GROUP 27A - On-vehicle Service ).

Q. Is the check result normal?
Go to Step 15.
Replace the rear wheel hub assembly <RL> (Refer to GROUP 27A - Rear axle 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?

Go to Step 16.

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) : Replace the rear wheel hub assembly <RL> (Refer to GROUP 27A - Rear axle hub assembly ).

STEP 16. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or more for more than 30 seconds.
note The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h or higher.

Q. Is the diagnosis code No.C1048 set?
Replace the hydraulic unit (ABS-ECU) (Refer to ). Then go to Step 17.
This diagnosis is complete.

STEP 17. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Drive the vehicle at 20 km/h or more for more than 30 seconds.
note The ABS warning lamp does not turn OFF in some cases unless the vehicle runs at 20 km/h or higher.

Q. Is the diagnosis code No.C1048 set?
Return to Step 1.
This diagnosis is complete.