Anti-Lock Braking System (ABS)
The contents of this article and images reflect the changes identified in TSB-11-35-001.HYDRAULIC UNIT CHECK
Required Special Tools:
^ MB991958: M.U.T.-III Sub Assembly
^ MB991824: V.C.I.
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
CAUTION:
^ The roller of the braking force tester and the tire should be dry during testing.
^ When testing the front brakes, apply the parking brake. When testing the rear brakes, stop the front wheels with chocks.
1. Jack up the vehicle. Then support the vehicle with rigid racks at the specified jack-up points or place the front or rear wheels on the rollers of the braking force tester.
2. Release the parking brake, and feel the drag force (drag torque) on each road wheel. When using the braking force tester, take a reading of the brake drag force.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
3. Connect scan tool MB991958 to the data link connector.
4. After checking that the selector lever is in "P" range, start the engine.
5. Select "Interactive Diagnosis" from the start-up screen.
6. Select "System Select."
7. Choose "ABS" from the "CHASSIS" tab.
8. Select "Actuator Test" from "ABS" screen
9. Choose an appropriate item for hydraulic unit check.
NOTE: The ABS system will switch to the scan tool mode and the ABS warning light will illuminate.
NOTE: When the ABS has been interrupted by the fail-safe function, scan tool MB991958 actuator testing cannot be used.
10. Turn the wheel by hand and check the change in braking force when the brake pedal is depressed. When using the braking force tester, depress the brake pedal until the braking force is at the following values, and check that the braking force changes to the brake drag force reading taken in step 2 when the actuator is force-driven. The result should be as shown in the diagram above.
11. If the result of inspection is abnormal, repair according to the Diagnosis Table below.
Diagnosis Table:
12. After inspection, disconnect scan tool MB991958 immediately after turning the ignition switch to the "LOCK" (OFF) position.
HYDRAULIC UNIT INSTALLATION ADJUSTMENT
- Refer to Hydraulic Unit removal and installation.
1. Operate the pre-removal steps for the hydraulic unit.
2. Remove all brake tubes.
3. Remove the protector.
4. Loosen the mounting bolt and nut of the hydraulic unit bracket.
5. Install all brake tubes temporarily.
6. Shake hydraulic unit in all directions with both hands to make the hydraulic unit bracket insulator fit with the unit.
7. Install the hydraulic unit bracket with mounting bolts and nuts not to load the brake tube.
8. Install the protector.
9. Install all brake tubes securely
NOTE: Install the flare nut taking care not to let the brake tube turn together.
10. Operate the post-installation steps of the hydraulic unit.
IN THE EVENT OF A DISCHARGED BATTERY
WARNING: If the ABS is not operating, the vehicle will be unstable during braking, Do not drive the vehicle with the ABS-ECU connector disconnected or with the ABS not operating.
If the engine is started using a booster cable when the battery is completely flat, and the vehicle is then driven without waiting for the battery to be recharged, the engine may misfire and it may not be possible to drive the vehicle. This is because the ABS consumes a large amount of current when carrying out its initial checks. If this happens, recharge the battery fully.