Porsche 928 Workshop Manual page 581

24128
Fuel System - Electronic Control
928 54
928 GT
This LH/EZK diagnosis/troubleshooting plan is based on the contents of the fault memory.
Paths not included in the self-diagnosis can be diagnosed by conventional means (test points 12 - 22
on LH, 12 16 on EZK)
Preconditions for troubleshooting are that the person performing the tests
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is familiar with the location of compopnents and the functions of and technical inter-relationships
between the systems to be tested (model information)
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can read and evaluate Porsche wiring diagrams
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knows the functions of electrical circuits and relays
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can use testing equipment such as oscilloscopes, voltmeters, ohmmeters and ammeters and
knows how to evaluate their readings.
Important:
A fault indication on the display (fault list in the case of the flashing code) does not always indicate
that the component in question is defective. It can also suggest a fault in the corresponding control
unit or the connecting leads (paths) between the component and the control unit.
No troubleshooting involving disconnecting plugs etc. is to be performed with the engine running
before the fault memory has been read out, or this in turn may be stored as a fault in the memory.
Note on the 9288 system tester
If the tester display shows
Fault fQ&taa& this may mean:
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Fault is no longer present at the time of testing (loose contact)
Remedy: visual inspection of the path, erasure of the fault memory and a repeat test drive.
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The conditions in which the fault is being tested for do not correspond to those under which the
fault originally occurred.
Remedy: conform with conditions displayed on the tester.
Sianal not olausible:
The signal from the monitored component is not within the tolerance range of the specified control-
unit value
D 24128 - 8 DME Diagnosing/Troubleshooting
Printed In Germany - Xxv, ,990