Before starting fault diagnosis
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Before starting fault diagnosis
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Before starting fault diagnosis, always do the following:
Warning
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No tests or connections are to be made on the SRS before the airbags have been disconnected.
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Read through
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Switch off the ignition.
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Undo the connection contact on the back of the driver and passenger airbags. Undo the 29-pin connectors under the front seats.
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Warning
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Splicing of SRS leads is strictly prohibited.
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Splicing can cause malfunctions that render the system unusable, which may result in injuries.
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Note
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If a connector is taken apart while the ignition is on, this is registered as a fault by the control module. The fault will not disappear until the connector has been put together and the fault code has been cleared, or until 50 detonation cycles have been performed.
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General information on fault diagnosis in electronic systems .
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Control module
When the control module is supplied with current, the processor in it is tripped. The processor then reads the instructions stored in the control module's memory.
The control module is programmed to read the inputs and activate the outputs. If the control module program is faulty, the diagnostic trouble code “Internal Control Module Fault”will be generated.
The control module must have a power supply if the system is to work. If the control module can be contacted by the diagnostic tool, this indicates that the module has power and that the processor is on the alert.
Outputs
The purpose of the system is to control a number of functions by means of various actuators, e.g. an injector or a lamp. For the system to be capable of performing its functions, it must be possible to activate the actuators. For this reason the actuators must be connected to the control module and have a proper power supply or ground connection.
Inputs
A condition for the control module's capability of controlling its actuators is that the system's sensors supply the control module with correct values.
The function of the sensors can be checked using the diagnostic tool.
