Mar

Display

Specified response/value

Troubleshooting, if specified value not met. Refer to circuit diagram when trouMeshooUng.

Digital display Unit

Disconnect sensor plug and bridge coupling plug (sleeve side! Repeat test. If display now OK, replace speed sensor. If display still above specified value, leads from control unit plug terminals 6 and 4 are defective Inspect a leads for chafing.

0 gital display

100 mV

As under 12.1 but applies to leads from control unit plug terminals 23 (11)* and 21.

Digital display

Witt

As under 12.1 but applies to leads from control unit plug terminals 8 and 9.

Digital display unit

As under 12.1 but applies to leads from control unit plug terminals 24 and 26.

Digital display unit

Replace control unit.

Indicator lamp does not light up:

1. Indicator1 lamp defective.

2. Switch off ignition. With ohmmeter, check diode between terminals 29 and 32 at removed control unit plug, in conducting and reverse directions. Display must register high resistance, then low resistance. For this operation, pull off right-hand multi-pin plug from combination instrument.

3. Check leads between terminals 29 and 32 for breakage.

Display out of tolerance:

1. Switch off ignition. Inspect leads from removed control unit plug between terminals 29 and 32 for breakage, also diode in conducting and reverse directions (see above).

2. Check lead between control unit plug terminal 29 and combination instrument (928 S, '84 model, terminal 2; 928 S '85 model onwards, terminal 3; 944, terminal 14, plug L) for breakage.

3. Check indicator lamp plug connection, also ground lead and valve relay plug connection for voltage drop.

If diode defective, replace hydraulic unit.

* Values in () apply to 928 S from '86 model onwards, 928 S 4, and 944 from '87 model onwards.

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Specified response/value

Troubleshooting, if specified value not met. Refer to circuit diagram when troubleshooting.

Display out of tolerance, indicator lamp does not light up:

1. Check indicator lamp and leads.

2. Pull out valve relay; lamp lights up; diode defective; replace hydraulic unit.

Indicator lamp must go out within 3 sees.

Indicator lamp does not go out:

1. Repeat test stage with engine running.

2. Replace control unit.

Indicator lamp must remain on while button depressed

Indicator lamp goes out:

1, Repeat test stage with engine running.

2. Replace control unit.

1. Repeat test stage with engine running.

2. Replace control unit.

1. Repeat test stage with engine running.

2. Replace control unit.

1. Repeat test stage with engine running.

2. Replace control unit.

FL = front left FR = front right RA = rear axle

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TEST PLAN 1 ABS

Switch ignition ON for all program switch positions

Program switch position

Item tested

Additional operations Ignition on

Display

Specified response/value

Troubleshooting, Refer to circuit à

15

Diode in reverse direction; indicator lamp

Note:

ABS indicator lamp glows less brightly, valve relay trips

Digital display unit

1. Check indicatD

2. Pull out valve ?

16

Control unit bite triggered

LED pushbutton pos. 4 lights up, depress button minimum 3 sees.

Note:

Lamp may flash twice while button depressed: pump motor startup

ABS indicator lamp in vehicle

Indicator lamp must go out within 3 sees.

Indicator tamp do

1. Repeat test sta

2. Replace contra

17

Control unit bite triggered with fault simulation

LED pushbutton pos. 4 lights up, depress button minimum 3 sees.

Note:

Lamp may flash twice white button depressed.

ABS indicator lamp in vehicle

Indicator lamp must remain on while button depressed

1. Repeat test stag

2. Replace contrai

pressure holding

LED pushbutton pos. 4 lights up; depress button again after each selected valve. Touching is suffient, with display at zero, press button again

Note:

Pump motor starts twice.

18.1 Valve FL

Depress button FL (pos. 5.2); depress LED pushbutton pos. 4

Digital display unit

2. Replace contra;

18.2 Valve FR

Wait until display registers zero! Depress button FR (pos. 5.3), depress LED pushbutton pos. 4,

Digital display unit

2. Replace controi

18.3 Valve RA

Wait until display registers zero! Depress button RA (pos. 5.4), depress LED pushbutton item 4.

Digital display unit

1.9 ... 2.3 A

1. Repeat test stage

2. Replace control

FL = front left FR = frontright RA = rear axle

Switch ignition ON for all program switch positions

Program

Item tested

Additional operations

Display

Specified

Troubleshoc

switch

Ignition on

response/value

Refer to cire

position

19

Control unit valve

LED pushbutton

-

flows —

pos. 4 lights up; depress

pressure reduction

button again after each

selected valve. Touching

is sufficient, with display

at zero, press button

again.

Note:

Pump motor starts twice.

19.1 Valve FL

Depress button FL

Digital display

4.8 .. . 6.0 A

1. Repeat te

(pos. 5.2); depress

unit

2. Replace c;

LED pushbutton

pos. 4.

19.2 Valve FR

Wait until display

Digital display

4.8 .. . 6.0 A

1. Repeat tei

registers zero!

unit

2. Replace a

Depress button FR

1

(pos. 5.3), depress

: 1

LED pushbutton

pos. 4.

Caution:

19.3 Valve RA

Wait until display

Digital display

4.8 ... 6.0 A

1. Repeat te

changed

registers zero!

unit

2. Replace c

sequence

Depress button RA

(pos. 5.4), depress

LED pushbutton

pos. 4.

24

Stop light switch

Apply brake pedal

Digital display

10... 15 V

If no display

unit

Check stop

Note*

and lead cor

Display of 0.00-

0.25 V without

Display less

pedal applied is

Correct trar

of no significance

switch.

23

Speed sensor signal

• Drive vehicle with

Digital display

> 1.5 (2.5)*

• Display o

front axle, then

unit

Dynamoi

Note:

rear axle in

Take lowest

see also page 11

sequence, on

value if dis

Display 0

dynamometer

play fluctuates

• Speed ser

• Engage brake rollers

Check ass

for front and rear

Note:

control ir

wheels separately.

If display

• Air gap b<

• Speed sensor

registers 1.5

• Check wh

F L = front left

selection occurs

(2.5)*, check

• Replace s

FR = front right

by depressing

air gap.

• Check nu

RA = rear axle

appropriate button

928 S bef

RL. = rear left

FL, FR and RL,

< 1.0

928 S '86

RR = rear right

RR (pos. 5.2,

Caution:

5,3 and 5.5, 5.6).

* Values in

19

. J

Display

Troubleshooting, rf apear«c «we apt met. Refer to circuit dnfr»m wrMci IsmMcsbooting.

Digital display

I unit

4.8 ... 6.0 A

2. Replace contra jn -

|

4.8 .. . 6.0 A

1, Repeat test stsge with engine running.

2. Replace cfjhtroi unit.

I Digital display i unit

4.8 .. , 6.0 A

1. Repeat test stage with engine running.

2. Replace control unit.

1 Digital display

I HRlft

Check stop light switch, adjustment, power supply to switch, plug connections and lead connection from control unit plug terminal 25 to stop light switch.

Correct transfer resistance in plug and lamp connections or replace stop light switch.

D^ital display

Take lowest value if display fluctuates

Note: If display registers 1,5 (2.5)*, check air gap.

< 1.0

• Display of999 signifies: Dynamometer speed excessive (over 15 kph)

• Speed sensor wrongly connected?

Check assignments. Speed sensors must correspond to specific wheels and control instrument inputs.

• Air gap between speed sensor and ring gear excessive. Check installation.

• Check wheel bearing clearance on front wheels.

• Replace speed sensors.

• Check number of teeth of pulse gear: 928 S before '86 = 90 teeth

928 S '86 modei onwards and 944 '87 model onwards = 45 teeth

Caution: Carry out test stages 20 - 22 when test stage 23 passed satisfactorily.

* Values in (} applicable to: 928 S '86 model onwards, 928 S 4, and 944 '87 model onwards.

* Values in (} applicable to: 928 S '86 model onwards, 928 S 4, and 944 '87 model onwards.

not obtained with the foot. >1/22 is 2000 N (200 kp)

I pushbutton.

»meter display stabilizes.

bconds.

jjght up. If it does, repeat jnds, i. e. wait approx. Pushbutton (internal test

[pushbutton, pos. 5,2. irce display registers

I left) must occur, ss FR button and hdbrake; test stages 20,

I wheel about to be tested, constant 2000 N. Do not jimeter display stabilizes instant at other running wheel,

|force are permissible, but do jin on both wheels. 20, 21 and 22

ivated, facilitating brake d maintain constant ch to adjust braking force!

ter display stabilizes

Specified response/value

Front axle

Lamp 1 (green) must remain on throughout

Rear axle

After a period of low pressure, braking force display rises again to: at front axle:

Lamp 1 (green) must remain on throughout at rear axle: <1000 N <(100 kp)

After dropping pressure twice without recirculating pump, the pump will switch on briefly.

Braking force display must then drop below <600 N < (60 kp}

Brake pedal resists slightly.

Lamp 1 (green) must remain on throughout.

Troubeshooting, if specified value not met

• Repeat test stages with engine running, making sure that braking force is not changed during testing.

• If lamp 2 (red) lights up, charge battery and run engine,

• Existing braking system OK? Properly bleded?

Brake line connections not leaking? Brake linings must not be badly worn. Brake discs OK?

Master and wheel brake cylinder OK? Wheel brake cylinders and linings. Must move freely, clean if necessary.

• Brake lines wrongly connected to hydraulic unit?

• Re-check asignment of brake rollers to pushbutton FL, FR and RA.

• Check ground terminals at pump motor and vehicle body. Re-check positive terminal of pump motor.

• Replace hydraulic unit.

Notes on test stage 21:

A noticeable reduction in pressure must have occurred before the registered specified value is reached (wheel braking force reduced).

If pressure rises immediately after application of reset button on test unit, the hydraulic lines assignment or cable harness must be checked for correct connection. If necessary, replace hydraulic unit.

Notes on test stage 22:

Yellow button must be kept depressed until braking force rises again (approx. 5 sees.).

End of test stage is signified by a steep rise in braking force.

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TEST PLAN 1 ABS

Switch ignition ON for all program switch positions

Program switch position

Item tested

Additional operations Ignition on

Specified response/vaiue

20

Hydraulic unit, pressure reduction in brake lines

Run engine if undervoltage occurs or braking force not obtained with the foot. Braking force on dynamometer for test stages 20/21/22 is 2000 N (200 kp) for front axle, 1000 N (100 kp) for rear axle.

1. Observe correct sequence of operations

• Select test stage (program switch position).

• Select channeljwheel).

• Set braking force with the foot, front axle 2000 N (200 kp), rear axle 1000 N (100 kp).

• After short delay (approx, 0.5 s), depress LED pushbutton.

• Keep LED pushbutton depressed until dynamometer display stabilizes. The internal test unit program runs for a few seconds,

• During test procedure, lamp 2 (red) must not light up. If it does, repeat test with engine running.

• Resume or repeat test only after approx. 20 seconds, i. e. wait approx.

20 seconds between two applications of LED pushbutton (internal test unit program must be concluded).

2. Check brake lines for correct connection

• Drive vehicle with front wheels on dynamometer.

• Select test stage 20, then front left wheel with pushbutton, pos. 5.2,

• Engage front left brake roller.

• Apply brake pedal, keep down until braking force display registers 2000 N (200 kp) on dynamometer.

• Depress LED pushbutton.

• Reduction in pressure to selected wheel (front left) must occur.

• Carry out same test on front right wheel. Depress FR button and engage only the front right brake roller.

3. Front axle hydraulic unit test; apply handbrake; test stages 20,

21 and 22

• Select one wheel (front left or front right).

• Engage both brake rollers.

• Preapply 2000 N (200 kp) braking force to the wheel about to be tested, with brake pedal. Throughout the test, maintain constant 2000 IM. Do not use a brake pedal winch to adjust braking force!

• Keep LED pushbutton depressed until dynamometer display stabilizes and value has been read off (approx. 6 sees,).

• During test, check that braking force remains constant at other running wheel.

If pedal travel varies: minor variations in braking force are permissible, but do affect the display!

• Carry out test stages 20, 21 and 22 in succession on both wheels.

4. Rear axle hydraulic unit test: test stages 20, 21 and 22

• Drive vehicle with rear axle on dynamometer.

• Depress pushbutton for rear axle.

• Engage both brake rolfers.

• Run engine (braking force reinforcement is activated, facilitating brake application).

• Preapply 1000 N (100 kp) with btrake pedal and maintain constant throughout test: Do not use a brake pedal winch to adjust braking force!

• Keep LED pushbutton depressed until dynamometer display stabilizes (test duration approx. 6 sees.).

Front axle

<1500 N

Lamp 1 (green) must remain on throughout

Rear axle <800 N

< (80 kp)

21

Hydraulic unit, pressure buildup in brake lines

After a period of iow pressure, braking force display rises again to: at front axle:

Lamp 1 (green) must remain on throughout at rear axle: <1000 M <(100 kp)

22

Hydraulic unit, pump output

After dropping pressure twice without recirculating pump, the pump will switc1" on briefly. Braking force dispsi« must then drop below <600 N <(60 kp)

Brake pedal resists slightly.

Lamp 1 (green) must remain on throughout.

ABS TEST UNIT Bosch ABS-2-LED TEster, order No. KDAS 0003

Adapter lead, order No. KDAS 0003/2 (supplied as standard with tester)

Wfp Pump Controller

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Standard tools and instruments

2 Control unit plug test leads, approx. 60 cm long with 2 insulated alligator clips and 2 flat pin plugs N 17.457.2.

The test lead must be used for testing the control unit plug. Plug terminal designations

Control unit multiple-pin plug, looking towards plug terminals.

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EXPLANATION OF THE ABS-2-LED Test Unit

This tester can be used to test the following peripheral system components in six program stages.

— Hydraulic unit

— Speed sensors

— Wiring harness

— Plug connections

— Stop light switch signal

— Generator signal

If a fault is present, it will be indicated by the various LED displays on the tester. Speed sensor signals can be evaluated by the deflection registered by the pointer-type instrument. The ABS regulating unit is not included in this Test Plan. This is a self-diagnostic unit which does not require additional testing with this test equipment.

ABS testing with this tester does not require a dynamometer. The tests can be carried out on a vehicle hoist of the type which leaves the wheels free to rotate.

If, in spite of this, a dynamometer is used, there is a danger that the vehicle may jump off the rollers. The responsibility for using a dynamometer rests with the personnel carrying out the tests.

ABS-2-LE0 Tester Layout

Abs2 Led Tester Kdas 0003

1 — 1 LED display for wheel speed in program switch position 6

2 - 1 LED display for battery voltage

3 - Program switch

4 - 7 LED displays for program switch position 1 5-2 LED displays for program switch position 2

6 - Adapter lead for connection to ABS wiring harness in vehicle

7 — Pushbutton for motor relay activation in program switch position 3

8 - 1 LED display for program switch position 3 9—2 LED displays for program switch position 4

10 — 3 LED displays for program switch position 5

11—2 Pushbuttons ro release solenoid valve functions, pressure-holding and pressure-reduction in program switch position 5

12 - Rotary switch for selection of individual wheels;

functions in program switch positions 5 and 6

13 — Pointer-type instrument for program switch position 6

Description of symbols

The tester draws its power supply from the vehicle battery. The supply voltage is monitored in all program switch positions throughout the entire test procedure. An LED (1) provides a continuous indication of a satisfactory power supply.

Program switch position 1

1 = LED display for ground connection 1

2 - LED display for ground connection 2

3 = LED display for diode activating warning lamp

4 = LED displays for internal resistance of solenoid valves in hydraulic unit and valve relay in OFF condition.

4.1 = LED display for front left wheel

4.2 = LED display for front right wheel

4.3 = LED display for rear axle of vehicles with 3-channel hydraulic unit (figures in () apply).

4.4 = No function applicable to Porsche vehicles (broken line signifies that LED must only light up for 4-channel hydraulic units).

r

31

I

m

o

o o

j.

1

i i 2 3

Program switch position 2

1 — LED display for connection to generator terminal 61

2 — LED display for connection to stop light switch o

Program switch position 3

1 — LED display for motor relay and recirculating pump in hydraulic unit.

2 — Pushbutton to activate motor relay.

LED display lights up only after pushbutton has been depressed.

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