Before replacing a control module
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Before replacing a control module
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When all checks have been carried out in accordance with the diagnostic
procedures described for the relevant diagnostic trouble code without any fault having been
detected, it is natural to assume that the control module is at fault. In view of the fact that the
control module is a component of extremely high quality and also very expensive, it is
important to verify the diagnosis as far as possible. Therefore, run through the following points
before definitely identifying the ABS control module as the cause of the fault.
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All wheels of the same diameter and width
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Correct inflation pressures in all wheels
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No play in wheel bearings Check once again that every single point in the fault
diagnosis procedure for the relevant diagnostic trouble code has been covered.
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2.
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Study the wiring diagram of the relevant circuit and make sure you understand
how it works. Appropriate parts of the technical description and the descriptions of operation
of electrical circuits in Service Manual 3:2 "Electrical system, wiring diagrams" may be of
assistance in this respect.
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3.
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Check all grounding points. If you have already done so, do it once
again. Check that power ground and signal ground are electrically and physically separated.
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4.
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Check the control module's power supply.
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5.
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Clear the diagnostic trouble code. Drive the car on test once more. If the original
fault still persists in spite of this, the ABS control module will have to be replaced.
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All control modules are more or less sensitive to static electricity and, if handled
carelessly or incorrectly, may be damaged so seriously that they no longer work properly. It is
therefore important to ensure that the following rules are strictly observed whenever the
control module has to be removed or replaced for any reason.
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Avoid unplugging or removing the
control module unless absolutely necessary.
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Never touch the connector's contact pins and never position the control
module in such a way that the pins could come into contact with foreign objects.
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Before unpacking a new control module, ground the packaging to the car body.
Open the packaging as shortly as possible before installing the control module in the car.
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When carrying out any work on a control module, it is important to ground
yourself from time to time. This is particularly important when you have been sitting in the car,
when changing your position, or when moving round the car. It is even more important in
climatic conditions with very dry air (i.e. during the winter in countries with a cold climate).
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Avoid wearing clothes made of synthetic materials.
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In addition, always handle control modules that are suspected of being defective
in exactly the same way as one that is in perfect working order. This will greatly improve your
chances of determining the cause of the fault.
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