System Test (ABS and ABS/TC)
System test (ABS and ABS/TC)
Important notes
1. A system test (function test) must be performed if work is performed on the hydraulic unit No. 7, the speed sensors and the wiring harness or if the hydraulic unit is exchanged. This is the case after accident repairs, for example. This prevents electrical and hydraulic lines from being swapped and ensures flawless operation of the system.
2. A system test also has to be performed if certain brake lines are replaced, e.g. on the intermediate piece No. 8. Unintentional bending of the brake lines could lead to incorrect hydraulic allocation, despite the different thread sizes used (M12 x 1 and M 10 x 1).
3. The system test is not menu-prompted (program- guided).
The system test consists of several test steps and is performed via different menus. Observe the specified sequence when performing the system test.
The static test must be performed at the start of the system test.
Remedy any detected fault before proceeding with the system test.
On vehicles with TC, the version coding must be checked or corrected before the static test is performed.
4. As fewer test steps are required on vehicles with Solo ABS (without TC) (several components are not installed), the TC-specific test steps are not displayed in the corresponding menu during the Solo ABS system test.
Test step No. 1, Nos. 6...10, Nos. 18...19 and No. 24 are therefore not necessary (not possible) with the Solo ABS.
5. After the system test, take the vehicle on a test drive and make sure that a controlled braking operation (ABS control operation) is performed.
System test overview (ABS and ABS/TC)
NOTE: The static test must be performed at the start of the system test.
Locate and remedy any detected fault. Proceed with the system test only after the static test has been completed successfully.
Necessary test steps with ABS/ TC 5.3 (4-channel system):
Test step
1 Version coding (start of the test/possible only on vehicles with TC)
2 Static test
3...4 Stop-light switch and terminal 61 signal
5...8 MIL and information lights
9 Intake valve
10 Switch-over valve
11 Return pump operation
12...19 ABS solenoid valves (8 ea./function and incorrect allocation)
20...23 Speed sensors (function and incorrect allocation)
24 Engine speed information to ABS/TC control module
Necessary test steps with ABS 5.3 (3-channel system):
NOTE:
- On vehicles with Solo ABS, the test begins with the static test (test step 2).
- The test steps in brackets are not necessary (possible only with a 4-channel system).
Test step
(1) _________
2 Static test (start of test)
3...4 Stop-light switch and terminal 61 signal
5 ABS MIL
(6...10) _________
11 Return pump operation
12...17 ABS solenoid valves (6 ea. / function and incorrect allocation)
(18...19) __________
20...23 Speed sensors (function and incorrect allocation)
(24) __________
System test ABS and ABS/TC
Test of required display / Test step not OK required function Possible causes, elimination, notes
Test step 1
Select and call up the version coding.
Display according to transmission version (Tiptronic or manual transmission).
Present only for vehicles with Traction Control.
If necessary, select the Modify coding menu to change the coding.
Test step 2
Select and perform the static test.
Required display: 0 faults.
This test checks whether all parts of the system are present or whether all electrical components are connected. If necessary, remedy any existing fault before proceeding with the system test.
Test step 3
Call up the Input signals menu and select the stop-light switch.
Briefly actuate the brake. The stop light switch status (open or closed) is checked.
Required display: Change from "not actuated" to "actuated".
Perform troubleshooting analogous to test point 13 (stop-light switch / DTC 4340).
Test step 4
Call up Input signals menu and select terminal 61 signal.
Start the engine.
Required display: Signal present (engine not running: not present).
For troubleshooting, the status of terminal 61 (present or not present) also can be checked in the system "Alarm system" via the Input signals menu.
- If "not present" appears in the Tester display with the engine running, call up the system "Alarm system" and also check the status of terminal 61 there in the Input signals menu.
If the signal is present there, the fault lies in the wire between the ABS control module and the other control module. For troubleshooting, consult the wiring diagram.
If the terminal 61 signal is also not present with the system "Alarm system", continue with the next point.
- Bulb of Generator (MIL) in the instrument cluster faulty.
Perform a lamp test (lamp must light up when the ignition is switched on).
- Check the generator.
Test step 5
Call up the Drive links menu and activate the ABS MIL. The display must flash. With the ABS/TC, the TC-MIL is activated as well
Check bulb
- Check wiring between the instrument cluster and control module according to the wiring diagram.
Test step 6
Activate the TC-MIL in the Drive links menu.
The display must flash
Only on vehicles with TC. For vehicles with Solo-ABS, continue with test step 11
Troubleshooting analogous to test step 5
Test step 7
Activate the TC information light in the Drive links menu.
Display must flash.
Only on vehicles with TC. On vehicles with Solo ABS, continue with test step 11
- Troubleshooting analogous to test step 5
Test step 8
Activate the TC switch information light in the Drive links menu.
Display must flash.
Only on vehicles with TC. On vehicles with Solo ABS, continue with test step 11
- Troubleshooting analogous to test step 5
Test step 9
In the Drive links menu, test function of the intake valve in the hydraulic unit.
Only on vehicles with TC. On vehicles with Solo ABS, continue with test step 11.
- Perform troubleshooting analogous to test point 16 (diagnostic trouble code 5260).
Test step 10
In the Drive links menu, test function of the switch-over valve in the hydraulic unit.
Only on vehicles with TC. On vehicles with Solo ABS, continue with test step 11.
- Perform troubleshooting analogous to test point 17 (diagnostic trouble code 5265).
Test step 11
In the Drive links menu, activate the return pump. Return pump runs audibly.
Perform troubleshooting analogous to test point 12 (return pump fault / DTC 4266).
If necessary, open the front lid in order to hear the pump run.
Test steps 12 - 19
In the Drive links menu, check the inlet and outlet ABS solenoid valves in the hydraulic unit for function and incorrect allocation. Rotate all four wheels individually (one after the other according to the test-step sequence). When doing this, carefully follow the instructions in the Tester Display.
On the Solo ABS, the test of the rear-axle valves (test steps 16...17) can be performed on the right or left wheel.
Test step 12: Maintain pressure, front left
Test step 13: Reduce pressure, front left
Test step 14: Maintain pressure, front right
Test step 15: Reduce pressure, front right
Test step 16: Maintain pressure, rear left (or rear with Solo ABS)
Test step 17: Reduce pressure, rear left (or rear with Solo ABS)
Test step 18: Maintain pressure, rear right
Test step 19: Reduce pressure, rear right
(Test steps 18 and 19 only on vehicles with TC)
Test step "Maintain pressure" not OK:
- Hydraulic lines incorrectly allocated if the activated wheel locks up (precondition: Inlet valve activated with the F8 key). Incorrect allocation of electrical wires is another possibility if impermissible repairs were made on the wiring harness after accident repairs.
- Inlet valve faulty.
Test step "Reduce pressure" not OK:
- If the activated wheel does not alternately lock up and then rotate freely again but another wheel does this (precondition: the parking brake is not engaged and the selector lever of Tiptronic vehicles is in position "N"), the hydraulic lines are swapped.
- Outlet valve defective.
Troubleshooting
Perform troubleshooting analogous to test point 10.
Test steps 20 - 23
Check speed sensors for function and incorrect allocation.
To do this, go to the Actual values menu and select the wheel speeds there.
Rotate all four wheels individually. When each wheel is rotated, the speed allocated to the wheel must be displayed.
The non-tested wheel must be held when the test is performed on the driven axle.
Test step No.:
20 = Front left wheel
21 = Front right wheel
22 = Rear left wheel
23 = Rear right wheel
- Rotate the wheel on which the test step is not OK.
The non-tested wheel must be held when the test is performed on the driven axle.
If an indication for a different wheel now appears in the Tester display, the electrical wires are swapped (incorrect allocation of the speed sensors). This is normally not possible, but could occur if an impermissible repair was performed on the wiring harness after an accident repair.
- Perform troubleshooting analogous to test points 2 to 9 (depending on the wheel in question).
Test step 24
Check the engine speed in the Actual values menu. The current engine speed is displayed if the engine is running.
Perform troubleshooting analogous to test point 20 (Engine rpm information missing / DTC 5283).