«mm SPIWSi


«mm SPIWSi


PSD Diagnosis

The PSD system is diagnosabJe. The fault memory can be read with either a Flashing Code Tester 9268 or Porsche System Tester 9288.

In addition, drives can be operated with a Porsche System Tester similar to 911 Carrera 4 models. Flashing Code Tester 9268

PSD fault memory can be read with the 9268 Flashing Code Tester. Faults are displayed with a four-digit fault code, as already in other known systems.

Explanation of Fault Code Digits


1st digit 5 Control unit identification

2nd digit 1 Fault currently exists

2 Fault was experienced but not currently exist

5 No faults

3rd digit 1 - 3 Tens digit of fault type

4th digit 1 - 5 Units digit of fault type

PSD Fault Codes

Code (3rd / 4th Digits) Type of Fault

11 Transverse lock solenoid

12 Transverse acceleration sender - short/break

13 Transverse acceleration sender - not okay

14 Transverse lock - deviation in regulation

15 Control unit - faulty

21 Speed sensor front left

22 Speed sensor front right

23 Speed sensor rear right

24 Speed sensor rear left

31 ABS solenoid front left

32 ABS solenoid front right

33 ABS solenoid rear axle

34 Solenoid relay

35 Return delivery pump

Tire Pressure Control System (RDK)

Safety at high road speeds depends chiefly on correct inflation pressure in the tires. Frequently reductions in pressure of 0.5 bar will not be recognized in normal driving.

A tire pressure control system (RDK) developed by Bosch GmbH and Porsche AG has been applied very successfully in Porsche racing cars in the past few years,

Possible tire damage was detected already in the initial stage before the damage could lead to a critical driving situation.

Air pressure loss while driving can be recognized with this tire pressure control system and the driver is informed of this by a display in the instrument cluster.

In this manner it is possible to have an early warning about initial stage tire damage and tread wear due to insufficient inflation pressure.

Correct tire pressure guarantees optimum car handling and low fuel consumption. Diagram Drawing of Tire Pressure Control System

1 - RDK control unit

2 - Instrument cluster

3 - RDK warning lamp

4 - ABS control unit

5 - Pressure switch

6 - High frequency sender

7 - ABS speed sensor



1 - Control unit

2 - Instrument cluster

3 - Deflector

4 - High frequency sender, front


5 - High frequency sender, rear

6 - 2.5 bar diaphragm press, switch, front

7 - 3,0 bar diaphragm press, switch, rear

Description of System

Two diaphragm pressure switches (3), which are screwed in the rim well with 180° spacing, are provided for each wheel. The diaphragm of a pressure switch receives tire pressure and acts as a switch for an electric oscillating circuit integrated in the diaphragm pressure switch. This electric oscillating circuit remains made as long as the tire inflation pressure is greater than a predetermined nominal switch pressure.The pressure switch will break the oscillating circuit, if the tire pressure drops below the nominal value.

Each wheel has a high frequency sender (2) on wheel carrier (1). High frequency senders are connected with the RDK control unit. Each high frequency sender produces an electromagnetic field on the sender end, which is directed toward the diaphragm pressure switches. Diaphragm pressure switches pass the high frequency sender as the road wheel turns. In this manner the oscillating circuit of the diaphragm pressure switch is brought into the sphere of influence of the high frequency sender's electromagnetic field.

Inductive coupling is produced between the high frequency sender and diaphragm pressure switch.

Current flows In the pressure switch oscillating circuit when the tire pressure is correct (pressure switch oscillating circuit made), since the oscillating circuit acts as a consumer because of the circuitry design. This additional power consumption is recognized and processed into voltage pulses in the RDK control unit. These voltage pulses are compared with the wheel speed pulses of the ABS control unit.

Sufficient tire inflation pressure is recognized by the RKD control unit, if there are two high frequency sender pulses for each revolution of the road wheel. With less than two pulses the RDK control unit recognizes insufficient tire inflation pressure and displays pertinent warnings in the instrument cluster. RDK control unit is located in the driver's footwell.

Function of Diaphragm Pressure Switches

Diaphragm (7) bears on contact pin (4), In other words the switch is closed, if tire pressure (6) is greater than reference pressure (5). Diaphragm and contact pin act as a switch in the electric oscillating circuit, consisting of capacitor (9) and coil (10).

Location of Components

Front Axle

Rear Axle

1 - Wheel carrier

2 - High frequency sender

Diaphragm Pressure Switch Function Diagram

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