Possible causes of deviations

Air gap at speed sensor is too large / too small

(check installation).

Pulse wheel is damaged or corroded.

Damage to wheel bearing (wheel bearings are not adjustable).

Fault, Fault Code Possible Causes, Elimination, Remarks

General procedure as for fault code - 21 -

1. Internal resistance / continuity between PIN 47 and PIN 46 at control unit plug.

Plug connections*: on right spring strut and on spring strut mount at right of trunk.

2. Speed sensor signal: if the ABS tester is used, turn the wheel selector switch to the front right wheel.

General procedure as for fault code - 21 -

1. Internal resistance / continuity between PIN 42 and PIN 43 at control unit plug.

Plug connections*: 1 x on right rear axle trailing arm and 1 x above the right rear axle stabilizer bearing.

2. Speed sensor signal: if the ABS tester is used, turn the wheel selector switch to the rear right wheel.

General procedure as for fault code - 21 -

1. Internal resistance / continuity between PIN 44 and PIN 45 at control unit plug.

Plug connections*: 1 x on left rear axle trailing arm and 1 x at rear left, close to clutch and brake hose on transmission.

2. Speed sensor signal: if the ABS tester is used, turn the wheel selector switch to the rear left wheel.

* For distinguishing feature between speed sensor wire and brake pad wear sensor wire, see Page D39/45 - 13.

7: Front right speed sensor

8: Rear right speed sensor

9: Rear left speed sensor

Fault, Fault Code

Possible Causes, Elimination, Remarks

10: Front left ABS valve

Fault code - 31

Certain faults in the ABS valve area (short to positive side or to earth/ground) in a control wire) can also be shown as a valve relay fault by the 9288 system tester.

A fault in the ABS valve circuits is normally memorized as an ABS valve fault in the control unit fault memory.

When the fault memory is read out, it is possible in the above situation for 2 faults to be displayed (ABS valve and valve relay).

1. Switch off the ignition and pull the plug off the control unit. Check PIN 19 of plug against PIN 17 and against PIN 23 for continuity. If necessary, interrupt the circuit (plug at hydraulic unit) and localize the break by reference to the circuit diagram.

2. Pull off the valve relay (7 pole) at the hydraulic unit.

Check for a short to the positive side or to earth/ground in the circuit as described in Item 1, by measuring at PIN 19. If a fault is detected, interrupt the circuit as described in Item 1, in order to localize the incorrect short-circuit to the positive side or to earth/ground.

3. Check resistance between PIN 19 of the plug and terminal 30 at the valve relay base.

Desired value approx. 1...2 Q.

611A-D39/45

Fault, Fault Code Possible Causes, Elimination, Remarks

If desired value is obtained: proceed with Item 4.

If desired value is not obtained:

Pull off the 12-pole plug at the hydraulic unit (a Torx wrench is needed to relieve tension).

Check internal resistance of ABS solenoid valve. Measure between PIN 1 and PIN 4 (at the hydraulic unit). Desired value 0.7...1.7 Q.

If desired value is incorrect: renew the hydraulic unit.

Push Pull Solenoid Not Energized

613-D39/45

4. Check whether the valve relay is energized (electric current present at solenoid valves).

To make this check, connect all plugs and the relay. Push back the protective cap on the locking valve block plug. Switch the ignition off, then on again.

The voltage from the car's electrical system must be present at PIN 1 and PIN 2.

If no power supply is present: continue with fault code - 34 - (valve relay). Comply with testing notes.

If the power supply is present, renew the PDAS/ABS control unit experimentally (output stage defective).

911 Carrera 4 All-Wheel Drive / Antiblock System

Fault, Fault Code Possible Causes, Elimination, Remarks

Testing notes

If a power supply plug to the solenoid valves (ABS or differential lock) is pulled off while the ignition is switched on, the valve relay will be de-energized. It is not re-energized when the plug is reconnected until the ignition has been switched off and on again.

11: Front right Comply with note under 10: Front left ABS valve,

ABS valve and with *au,t cocle "31

When troubleshooting, proceed as for fault code - 31 -, but use PIN 22 instead of PIN 19 on the control unit plug.

To check the internal resistance of the ABS valve (after pulling off the 12-pin plug at the hydraulic unit), measure between PIN 3 and PIN 4 (instead of PIN 1 and PIN 4).

12: Rear axle Comply with note under 10: Front left ABS valve,

ABS valve and with fault code - 31 -.

For troubleshooting, proceed as for fault code - 31 - but use PIN 2 instead of PIN 19 on the control unit plug.

To check the internal resistance of the ABS valve (after pulling off the 12-pin plug at the hydraulic unit), measure between PIN 5 and PIN 4 (instead of PIN 1 and PIN 4).

Fault, Fault Code Possible Causes, Elimination, Remarks

13: Valve relay Certain faults in the ABS valve area (short-circuit to positive side or

Fault code - 34 - earth/ground in a control wire) may also be shown as valve relay faults by the 9288 system tester.

A fault in the ABS valve circuit is normally memorized as an ABS valve fault in the control unit's fault memory.

In the case described above, when the fault memory is read out the display of 2 faults is possible (ABS valve and valve relay).

1. Switch off the ignition. Pull off the control unit plug. Check the control circuit (wire with relay) - from PIN 20 to PIN 7 - for breaks, short to earth/ground or short to positive side.

If no fault is found, proceed with 2.

If there is a break or a short to the positive side or to earth/ground, pull off the valve relay. Check the wires between terminal 85 on the relay base and PIN 7 on the control unit plug and between terminal 86 and PIN 20.

If the wires are in working order, renew the valve relay.

Fault, Fault Code

Possible Causes, Elimination, Remarks

2. Measure resistance between the following PINs at the control unit plug:

PIN 19 to PIN 17 PIN 22 to PIN 17 PIN 2 to PIN 17 Desired value approx. 1...2 Q

PIN 21 to PIN 23 PIN 18 to PIN 23 Desired value approx. 2...4 Q

If the desired value is correct, proceed to Item 3.

If incorrect values are obtained, localize the fault as appropriate.

From PIN 21 and 18 to PIN 23 = Differential locking valves + wiring

Re ABS valves and wiring

Pull off the 12-pole plug at the hydraulic unit.

Measure the internal resistance of the solenoid valves.

PIN 1 against PIN 4

PIN 3 against PIN 4

PIN 5 against PIN 4

Desired value not obtained: renew hydraulic unit.

613-D39/45

Fault, Fault Code Possible Causes, Elimination, Remarks

Re: differential locking valves and wiring:

Pull plug off valve block. Measure internal resistance of solenoid valves.

PIN 1 against PIN 3 and PIN 2 against PIN 4 Desired value 2...4 £2

If an incorrect value is obtained: renew the valve block.

Wire System With Ground Fault Diagram

609B-D39/45

3. Pull off valve relay (7-pole) at hydraulic unit. Measure at control unit plug PIN 17 in order to determine whether there is a short to the positive side or to earth/ground.

If necessary, interrupt the circuit at the hydraulic unit plug (12-pole) and localize the fault by reference to the circuit diagram.

4. Check that the power supply is present at terminal 87 of the relay base (car's electrical system voltage) when the valve relay is pulled off. Desired reading: approx. 12 Volt (car's on-board system voltage).

5. Measure resistance between terminal 87 a on the relay base and the earth/ground wire at the pump motor.

Desired value ~ 2...4 Q. It is essential for the earth/ground wire and the earth/ground point to be in working order. If necessary, renew the hydraulic unit (resistor in relay base has increased in value).

Wire System With Ground Fault Diagram

611B-D39/45

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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