Before changing a controlmodule
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Before changing a control
module
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When all tests have been carried out according to the relevant diagnostic
procedure without any faults having been found, it is natural to assume that the control
module is at fault.
In view of the fact that the control module is an extremely high-quality component and
also an expensive one, it is important to verify the diagnosis as far as possible.
Therefore, go through the following points
very
carefully
before definitely pointing to the control module or instrument as the cause of the
fault.
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Check once again that every single
point in the diagnostic procedure or checking schedule for the relevant diagnostic trouble code
has been carried out.
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Study the wiring diagram of the circuit in question and make sure you understand
how it works. Relevant parts of the technical description and the descriptions of electrical
operating principles in Service Manual 3:2 "Electrical system, wiring diagrams" may be of
assistance in this respect.
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Check all grounding points. If you have already done so, do so once
again.
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Check the control module power supply and fuses.
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Be restrictive in regard to control module replacement. Unnecessary control
module replacements constitute a major cost to Saab Automobile and Saab dealers.
Think of all possible causes of the fault before changing the control module.
If a spare control module is fitted for testing purposes, always refit the correct control
module.
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If the original fault persists in spite of this, the control module will have to be
changed.
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