Porsche 928 - WORKSHOP MANUAL 1977 Workshop Manual page 152

928
Wheels, Tires, Alignment
44
Menu 1 = Fault memory
Reading out fault memory / eliminating faults
Important notes
Faults which were not present during the last journey and the test conditions applying them cam
nnt be measured (with one exception). The relevant fault should therefore be &pe&&y&
ally, since with this type of fault the cause is either poor electrical contact, contact resistance
or corrosion at the plug connections.
Exception:
I,
p (fault code l-4). This fault is always output by the system tester
as "Not. However, it is possible that the fault is present and can be measured by way of
the sensor test (menu 2).
- A displayed fault, for example "HF sensor around short", refers not only to the HF sensor but to
the complete circuit path as far as the control unit input.
After eliminating the fault, erase the fault memory. After a short test drive (approx. 500 meters),
read out the fault memory again.
The fault code for the fault output is displayed as additional information if button 1 is pressed.
In addition, from control unit software status R 02 on (introduced during 1991 model year), the
road speed when the fault first occurred is memorized.
If the 9288 system tester is connected, make quite sure that no speed range is selected at
the automatic transmission, since when the engine is running the tester could increase its
running speed.
Not all svstem faults are identified bv the RDK control unit as faults. This applies to the RDK con-
trol unit itself. If the fault display "RDK SHUT DOWN" appears and no fault is stored in the control
unit, the following points must be checked or confirmed before the RDK control unit is replaced:
a. Is the control unit plug attached correctly and are the connection contacts between the plug
and the control unit in good condition?
b. When the ignition is swftched on, a voltage higher than 9 Volt must be present at PIN 13
(ground) and PIN 33 of the disconnected control unit plug (refer to Page 44 - 34).
c. There must be no break in the data line from RDK control unit PIN 2 to instrument cluster plug
2, PIN 11.
The following display may appear as a fault output although no fault is present:
Rata line rnteri-uptiou - not present
_'
(fault code 18).
RDK-Diagnose
Printed in Germany - XXV, 1990
44 - 305