Pressure Transmitter Symbol

Program switch position 4

No function applicable to Porsche vehicles (928, 944) as no acceleration transmitter fitted.

Program switch position 5

Function testing of solenoid valves and valve relay in hydraulic unit. Testing of channel assignments of solenoid valves (interchange test).

1 — Pushbutton and LED display for pressure reduction function. LED must light up when button depressed.

2 — Pushbutton and LED display for pressure-holding function. LED must light up when button depressed.

3 — LED display for valve relay function.

LED must remain lit continuously in program switch position 5.

4 — Symbol for solenoid valves.

Solenoid Switch SymbolPressure Transmitter Symbol

Switch for wheel selection

In program switch position 5 and 6, the switch must be set to the wheel to be tested.

1 — Rotary switch for wheel selection

4 — Rear left wheel, when testing speed sensor in program switch position 6 (left signal represents rear left)

Rear axle on vehicles with 3-channel hydraulic unit when testing solenoid valve and valve relay in program switch position 5 (right symbol).

5 — Rear right wheel, when testing speed sensor in program switch position 6.

Program switch position 6

Testing of speed sensor signal and change in dynamic air gap between speed sensor and ring gear. Test for incorrect assignment of speed sensors.

1 — Pointer-type instrument

2 — LED display for rotary movement of wheels.

LED remains on continuously so long as sufficient wheel speed exists for testing. Do not take reading from indicating instrument before this condition is obtained.

ABS-2-LED Tester connection

1. With ignition switched OFF, disconnect multi-pin (35-pole) plug from control unit

2. Connect ABS-2-LED tester to ABS wiring harness multi-pin (35-pole) plug by means of adapter lead plug.

3. Switch ignition ON. All other power-consuming systems must be switched off. CAUTION: Vehicle must not be driven with test unit connected.

Tester connection 928 Series

Tester connection 944 Series

Abs Led Tester

Preparations for tests using the ABS-2-LED Tester

♦ Check ground connection of recirculating pump and overvoltage protection relay terminal 31 for secure attachment and corrosion.

• Check hydraulic connections and junctions on hydraulic unit for leaks (visual inspection).

• If, when driving, the ABS warning lamp lights up intermittently (e.g. when items of electrical equipment are switched on) and goes out of its own accord, check battery and power supply (generator, regulator and voltage drops).

• If the ABS warning light remains on and does not go out, check the following points:

- Is multi-pin plug correctly installed (and locked) in control unit?

- Are all plug contacts OK?

— Are spring-loaded contacts locked in position?

- Are V-belts cracked? (generator produces no voltage, charging and ABS warning lamp lights up).

For testing operations, switch ignition ON in all program switch positions (tester operates on power supply from vehicle battery).

Observe LED for power supply in all program switch positions.

Switch ignition ON for all program switch positions

Item tested (measured at terminals)

Additional operations

Specified response (display)

Possible causes of fault Refer to circuit diagrar

Power supply (terminal 20/ground and terminal 1/positive)

Ignition ON

Ground connections (terminals 34, 10), diode for warning lamp (terminals 29, 32) solenoid valves, internal resistances (terminals 2, 35, 18) valve relay OFF condition and ground connection

Ignition ON

remains on continuously

First6 LEDs glow with uniform brightness

LED does not remain o

• Battery insufficient!*

• No voltage at termir

— No voltage at terr terminal 30 interr

— Relay or diode in 31, passage in one

• Excessive voltage dr<

928 S, '84 model 928 S, '85 model on 944, '87 model onw.

Check ground conne • LED -Kj- does noi

— Lead between coi '84 model: termir interrupted.

Excessive voltage or valve relay plu

Test with ohmmei switched OFF. Display must regi direction. (Pull out yellow

If specified result:

— Leads from con ectfied response isplay)

mins on rrtinuously

Possible causes of fault.

Refer to circuit diagram when troublediooting.

LED does not remain on continuously:

• Battery insufficiently charged low rage < 9.9 V

• Fuse blown (928 S '84 model fuse in ABS relay: 35 model onwards: fuse 16 cm CEB; 944: fuse 26 on CEB).

• No ground at terminal 20 of control unit plug (test with ohmmeter).

• No voltage at terminal 1 of control unit plug.

- Lead from terminal '87 of ABS relay* to terminal 1 of control unit plug interrupted.

- No voltage at terminal 30 of ABS relay, as positive lead from battery + to ABS relay terminal 30 interrupted.

- No voltage at terminal 15 to ABS relay.

- Relay or diode in relay defective (test diode with ohmmeter between terminals 30 and 31, passage in one direction only).

• Excessive voltage drop in supply leads.

928 S, '85 model onwards = relay XVI 944, '87 model onwards = relay G 20

does not light up:

Check ground connections between terminals 34, 10 and MP.

— ABS warning lamp defective.

— 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) interrupted.

— Excessive voltage drop at indicator lamp plug connection, valve relay ground connection or valve relay plug connection.

— Test with ohmmeter between terminals 29 and 32 of control unit plug with ignition switched OFF.

Display must register low resistance in conducting direction, high resistance in reverse direction.

(Pull out yellow plug from central information board for this test). If specified results not met, either:

— The diode is defective, replace hydraulic unit, or:

— Leads from control unit plug terminals 29 or 32 to hydraulic unit interrupted.

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