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DIAGNOSTIC MANUAL
IMPORTANT TERMS
These terms need to be understood before we start going through the diagnostics of SRS .
Loop
Resistance:
The resistance offered to current flow by the wiring from the SRS ECU to the individual
components (pretensioners & airbags) is called the loop resistance of that particular circuit. For the
effective functioning, each wiring circuit in the SRS system should be having its resistance value within a
certain limit. The SRS ECU will be monitoring the loop resistance continuously and will register DTCs if
the value is out of the defined range. The contacts are gold plated to prevent the variation of resistance
value due to oxidation.
If the resistance is less than the lower limit, the error will be registered under short circuit for that
particular circuit, as the wiring offers less resistance than required.
If the resistance is more than the upper limit, the error will be registered under open circuit for that
particular circuit, as the wiring offers more resistance than required.
Squib:
Terminal connectors at the airbag and pretensioner ends are called Squibs. They are provided with shunts,
which does not allow current flow unless and otherwise it is properly inserted in to the module. So it is
impossible to measure the continuity, voltage or resistance of these lines with multimeter.
Forceful insertion of the multimeter terminal will cause permanent damage to the squibs.
Important instructions
Never repair any wiring. It is always recommended to replace the wiring.
Never try to probe the Airbag or Pretensioner with multimeter. The current from the internal
battery of the multimeter may fire the component and deploy the airbags.
INTERMITTENT PROBLEMS
Check the following for intermittent problems
Poor mating of the connector halves/damage of connector locking
Terminals not fully seated in the connector body
Damage of harness and terminals
Connector pin separation from wire
Corrosion on pin contact points
The repair methods given by the manufacturer in this document are based on the technical specifications, current at the time of release. The methods may be modified as a result of changes introduced by the
manufacturer in the production of the various component units and accessories from which the vehicles are manufactured. The reproduction, translation, transmission, in part of or whole of the present document,
are prohibited without the prior written consent of Mahindra & Mahindra Ltd. The use of this document by any person other than the trained personnel, at the Authorized Service Centre of Mahindra & Mahindra Ltd.,
will amount to unauthorized use and shall be liable for penalty/prosecution© 2011 Mahindra & Mahindra Ltd.
SRS
MAN-00156
OCT 2011/Rev 1
5
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