Before changing a control module
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Before changing a control module
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When all tests and checks have been carried out in accordance with the diagnostics procedure for the relevant diagnostic trouble code, or by manual fault diagnosis, without any faults having been found, it is natural to assume that the control module is at fault. Check through the following points very carefully before definitely concluding that the control module is the cause of the fault.
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1.
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Check once again that every single point in the diagnostic procedure for the diagnostic trouble code in question has been carried out.
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2.
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Study the wiring diagram of the circuit in question and make sure you understand it. Relevant parts of the technical description and the electrical principles of operation described in Service Manual 3:2 "Electrical system, wiring diagrams" may be of assistance in this respect. The wiring diagram in this manual was finalized about 10 weeks before the start of production. In the event of any discrepancies between it and the wiring of the car you are working on, use the corresponding wiring diagram in Service Manual 3:2 "Electrical system, wiring diagrams" as a reference.
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3.
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In connection with removing and fitting the control module, bear in mind its sensitivity to electrostatic discharges. See
for more detailed information.
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4.
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Check all grounding points and the power supply to the control module. If you have already done so, do it once again. Make sure that power ground and sensors are mechanically and electrically isolated, see
.
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5.
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If the proposed fault diagnosis procedure does not produce satisfactory results, try to trace the fault by measuring and analysing
, see
. Connect a BOB or SIM.
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6.
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It has been our experience in previous years that 80%% of all control modules returned in connection with repairs carried out under warranty are in proper working order. Be restrictive with control module replacement. Unnecessary control module replacement represents a major cost for Saab Automobile AB and Saab dealers. Think through all conceivable causes of the fault before changing the control module. When another control module is fitted as a test, always refit the right control module.
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7.
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If the original fault persists in spite of this, then the control module will have to be changed.
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