Test 10 - Hydraulic Unit, Pressure Build-up, Pressure Hold

TEST SEQUENCE
1. Connections needed:
- T-plug (4a) with adapter (A) at Antilock Brake System (ABS) wire harness (1)
- T-plug (4b) at ABS control unit (2)
- Connecting lead at adapter (A) to cigarette lighter - red telltale lamp comes "On"
2. With front axle on BPS and flashing "*" on tester, set to FRONT LEFT/RIGHT: (down arrow).
3. Turn "On" ignition, note voltage between leads 1 and 10 (if necessary at idle speed), BPS switched "On" for both wheels.
4. Apply brakes until BPS reading is 1500 N, load axle if necessary, maintain this pedal force steadily.
5. Press acknowledge button. After 2 sec. pump is activated, valve opened for approx. 4 sec. and brought to the retention phase after a brief pressure buildup and the "s" display is started. When 5 seconds are displayed, press acknowledge button.
6. Repeat: acknowledge button, next wheel (down arrow), test positions: FRONT LEFT/RIGHT, REAR LEFT/RIGHT in any desired order.





Nominal Values

7. Compare the displayed actual values obtained from the test equipment with the nominal values provided above. If nominal values are not obtained, proceed with the troubleshooting procedures below as needed.

TROUBLESHOOTING
Voltage Between Line 1 And 10
- Switch "On" ignition.
- Run engine.

Recharge, check battery.

Front Left - Right - Right/Left Rear Left/Right
- Due to high inrush currents, repeat test step with engine running.
- Refer to test step 05/06/07.
- A prerequisite for the ABS test is that the conventional brake system is in working order - System well bled, no leaks at brake line connections, brake pads OK., master and wheel brake cylinders OK.
- Ensure uniformity of wheels on one axle.

Check the lines to and from the hydraulic unit for leaks.
Replace hydraulic unit.