Lotus Evora - Theory of Operation

Lotus Service Notes Section WF
Page 7
Deployed Inflator Modules
WARNING: Safety precautions must be observed when handling a deployed inflator module. After de-
ployment, the air bag surface may contain a white packing powder used to ease deployment. Always
wear gloves and safety glasses when handling a deployed inflator module, and wash your hands with
a mild soap and water afterwards.
Inspections Required After an Accident
All SRS system components, including harnesses and brackets, must be inspected after an accident. If
any are damaged or bent, they must be replaced even if a deployment did not occur. If the SRS was deployed,
the following components MUST be renewed even if there is no visible damage to the parts:
• Driverairbagmodule;
• Passengerairbagmodule;
• Sensor&DiagnosticModule(SDM);
• Driverandpassengerpyrotechnicseatbeltassemblies;
• Rotaryconnector;
• Passengerairbagmountingbrackets(ifpassengerairbagwasdeployed);
• Mainfasciapanel(ifpassengerairbagwasdeployed);
Inspect the steering column for damage or telescoping (see Section HG) and column mounting brackets
for damage. Inspect the front subframe longerons, and the mounting of the two forward crash sensors for dam-
age or distortion. Inspect the chassis scuttle beam in the area of the passenger airbag mounting brackets for
damage or distortion. Inspect the SRS wiring harness and connectors for damage or any signs of overheating.
Inspect both front seat shells, and all seat mounting brackets and runners. Check all seat belt mountings and
brackets for damage or distortion.
Do not attempt to repair the steering column or chassis or any of the above mentioned components.
Service only by replacement.
WARNING: Proper operation of the SRS system requires that any repairs to the vehicle structure return
it to its original production configuration. Deployment, or any visible damage to the SRS components
and/or their respective mounting brackets requires replacement, not repair.
WF.7 - THEORY OF OPERATION
The key components of the Supplementary Restraint System (SRS) are the following:
• Sensor&DiagnosticModule(SDM);
• Forwardcrashsensors;
• Driverairbagmodule;
• Passengerairbagmodule;
• Rotaryconnector;
• Seatbeltpre-tensioners.
Sensor & Diagnostic Module (SDM);
The SDM is the main electronic control unit (ECU) of the SRS, and incorporates an accelerometer to de-
tect rates of forward deceleration in conjuction with two forward crash sensors. When data from these sensors
meets collision recognition criteria over a certain threshold, the SDM triggers as a single set, the driver and front
passenger airbags in either stage one or stage two mode, and both front seat belt pre-tensioners. Additional
functions are to maintain an electrical energy reserve in case of vehicle battery power interruption during the
accident, operation of a dash mounted tell tale lamp, and an electronic diagnostic and event recording facility
accessible via a workshop scanner tool.
The unit is mounted in an alloy box bolted to the centre underside of the chassis scuttle beam, accessible
from the footwells.
The following functionality is provided by the SDM;
• Sensingoffrontalimpactcrasheventsandvehiclespecificdiscriminationbetweenairbagnon-deployment
and stage one or stage two deployment-requiring events as well as activation of the front seat belt pre-