Output Diagnostic Test Mode (Function 03)

ABS/EDL and ABS/EDL/ASR ITT Mark 20 IE

Output DTM can be used to check the following:
^ Pump motor
^ Function of hydraulic circuit (allocation of brake lines to wheel brakes, and the function of valves).
^ Hydraulic circuit for leaks or interchanged lines.

Notes:
^ The vehicle must be raised so that wheels can turn freely (a second technician is needed to turn the wheels).
^ The - C - button can be pressed to discontinue the test procedure at any time.
^ To avoid overloading tested items, activate only 60-90 seconds. Output DTM is discontinued if (arrow) button is not pressed within this time period.
^ The warning light for ABS and the red brake warning symbol flash during the output DTM.
^ After numerous activations of the brake pedal the vacuum in the brake booster is reduced. Therefore more force must be applied to the brake pedal in order to attain the same fluid pressure in the brake system.
^ With reduced pressure from the brake booster it can happen that the wheels will not lock. Start engine to raise vacuum.

Examples

Indicated on display (for example)
FL - front left
FR - front right
RL - rear left
RR - rear right
I - inlet valve
0 - Outlet valve
VBAT - Battery voltage; voltage to valve
0V - 0 Volt; no voltage to valve
Locked/free - Wheel condition; must be tested by second technician

Indicated on display, example (only for vehicles with ATC)
Hydr - P = Hydraulic pump

- Release parking brake.
- Connect VAG1551 and select address word 03 "Brake Electronics". Scan Tool VAG1551/1552 or VAS5051 Connecting/Selecting Function
- Ignition must be switched on.
- Check control module version and press (arrow) button. Check Control Module Versions (Function 01)

Indicated on display
- Press buttons 0 and 3 for function "Output diagnostic test mode."

Indicated on display
- Press Q button to confirm input.

Legend to the following illustrations:
1. Low pressure memory
2. Motor with pump
3. EDL-Intake valve (hydraulic)
4. Noise deadener cavity
5. EDL-change over valve/separation valve(electrical) with integrated hydraulic pressure relief valve
6. Front inlet valve
7. Front outlet valve
8. Front wheel
9. Rear inlet valve
10. Rear outlet valve
11. Rear wheel

Indicated on display

The Hydraulic pump ABS - V64 - 2 must run. It can be heard.

When you press the brake pedal, feel how it vibrates. The hydraulic pump creates pressure pulses in the brake lines which cause the vibrations. The pressure pulses in the brake lines are not enough to lock the wheels.
The hydraulic circuit diagrams in the following informtion represent an ABS/EDL system. Only one of the two brake circuits is shown. These diagrams help in the understanding of the individual test steps of the output diagnostic test mode.

- Press (arrow) button.

Indicated on display
- Press (arrow) button.

Indicated on display
Brake pedal should not give way.

When brake pedal is operated, brake fluid pressure builds up in all four wheel brake cylinders. The hydraulic EDL intake valve - 3 closes. Wheels lock.
This relies on the proper function of the mechanical/hydraulic components of the brake system. This means that brake master cylinder is able to build up pressure in all wheel brake cylinders and the hydraulic connections and lines are tight. In case the wheels do not lock, conduct a visual check on the brake fluid reservoir, brake master cylinder, hydraulic unit and wheel brake cylinders.

Notes: This test step conducts the "pressure build-up" phase of ABS - controlled braking.

- Press (arrow) button.

Indicated on display
Brake is still activated, the hydraulic EDL intake valve - 3 remains closed.

The inlet valve - 6 (in example: front left) is activated. It blocks the brake line. Brake fluid pressure in wheel brake cylinder is maintained. Wheels continue to be locked.

Notes: This test step conducts the "pressure maintenance" phase of ABS - controlled braking.

- Press (arrow) button.

Indicated on display
Brake is still activated, the hydraulic EDL intake valve - 3 remains closed.

Inlet valve - 6 and outlet - 7 are activated. Hydraulic pump - 2 runs and reduces brake fluid pressure in wheel brake cylinder via open outlet valve - 7 (in example: front left)
Brake pedal should not give way and presses stronger against the foot. Turn the wheel - 8 (in example: front left).
If wheel can not be turned, check if brake line for the front left wheel is connected correctly. If the line is connected correctly and there is no electrical malfunction in the system, there is a mechanical malfunction in one of the valves. Replace hydraulic control unit.
If brake pedal yields, the inlet valve or that which is parallel to the inlet valve return valve is leaking. Replace hydraulic control unit.

Notes: This test step conducts the "pressure - reduction" phase of ABS - controlled braking.

- Press (arrow) button within the next 10 seconds.

Indicated on display

Hydraulic pump - 2 ABS - V64 should stop running.
Continue to operate brake; the hydraulic EDL intake valve - 3 remains closed. Only inlet valve - 6 (in example: front, left) is activated and blocks the brake line. If inlet valve is without leaks wheel - 8 (in example: front left) can be turned.
If wheel can not be turned, inlet valve or return valve parallel to inlet valve is leaky. Replace hydraulic control unit.

- Press (arrow) button.

Indicated on display

Continue to activate brake; the hydraulic EDL intake valve - 3 remains closed. Inlet valve - 6 (in example: front left) is no longer activated. It no longer blocks brake line. Brake pedal can be felt yielding. Brake fluid pressure builds up again in wheel brake cylinder (in example: front left). Wheel - 8 (in example: front left) is locked again.

- Press (arrow) button.

Indicated on display
- Press (arrow) button.

Continue the output diagnostic test mode to check front right, rear left and rear right wheels in sequence. The test steps for the front left wheel apply to all others so they are not described in detail.

Indicated on display
- Press (arrow) button.

Indicated on display
- Press (arrow) button.
Hydraulic pump ABS - V64 must run.
Brake pedal should not give way.

Indicated on display
- Press --> button within the next 10 seconds.
Hydraulic pump ABS - V64 stops running

Indicated on display
- Press (arrow) button.
Brake pedal must be felt yielding.

Indicated on display
- Press (arrow) button.

Indicated on display
- Press (arrow) button.
Hydraulic pump ABS - V64 must run.
Brake pedal should not give way.

Indicated on display
- Press (arrow) button within the next 10 seconds.
Hydraulic pump ABS - V64 stops running

Indicated on display
- Press (arrow) button.
Brake pedal must be felt yielding.

Indicated on display
- Press (arrow) button.

Indicated on display
- Press (arrow) button.
Hydraulic pump ABS - V64 must run.
Brake pedal should not give way.

Indicated on display
- Press (arrow) button within the next 10 seconds.
Hydraulic pump ABS - V64 stops running.

Indicated on display
- Press (arrow) button.
Brake pedal must be felt yielding.

Indicated on display
- Press (arrow) button.

Indicator on display:

EDL change over valve -5- is activated. Hydraulic pump ABS/EDL - V64 -2- runs for several seconds. It draws brake fluid through the open EDL intake valve -3- from the brake fluid reservoir. Hydraulic pump builds brake fluid pressure in the EDL - controlled wheel brake cylinder (front left and front right). Front wheels lock.
If this is not the case, there is a mechanical malfunction in one of the valves even if there is no electrical malfunction. Replace hydraulic control unit.

- Press (arrow) button.

Notes: Output diagnostic test mode has ended. Warning lamp for ABS and warning lamp for brake system switches off

- Press (arrow) button.

Indicated on display

Notes:
^ If the warning light for ABS does not switch off there is a malfunction in the system.
^ Adhere to test procedure exactly-first check and then erase DTC memory.

- Press buttons 0 and 6 for function 06 "End output" and confirm input with Q button.
- Switch ignition off.
- Disconnect Scan Tool.