Lotus Elise / Lotus Exige. Manual - part 107

Lotus Service Notes Section WD

Page 10

System fault detection, SDM self test: min. 8.0 V; max. 16.0 V
Below 10.0 V system readiness may be delayed by 3 s.
Below 9.0 V system readiness may be delayed by 10 s.
System fault detection and SDM self test are reduced as long as an undervoltage condition is detected, which
could already apply for supply voltages below 10.5 V.
Activation of airbags: min. 8.0 V; max. 16.0 V.
Activation of seat belt pre-tensioners: min. 10.0 V; max. 16.0 V.

Energy Reserve

Energy reserve capacitors within the SDM are provided to allow SRS deployment if the vehicle battery

power supply is interrupted during the time of vehicle impact. The capacitors provide full support of the
acceleration sensing and airbag initiation capability for a minimum of 150 ms after a loss of external power
supply, provided that before the loss, the SDM had been supplied with:
at least 10.0 V for at least 10 s; or
at least 9.0 V for at least 13 s; or
at least 8.0 V for at least 20 s.

The capacitors will be discharged down to a point where no initiation of airbags is possible within a max.

of 20 s after removal of the power supply.

WD.8 - SENSOR & DIAGNOSTIC MODULE (SDM)

To Replace SDM

WARNING: The SDM must be replaced after SRS deployment. Do not attempt to repair or reuse.

The SDM is mounted on a bracket riveted to the top of the passenger side scuttle beam, and is accessible

only after removal of the fascia (dash) top panel.

Follow the safety procedure detailed in sub-section WD.6 to turn off the ignition, disconnect the battery
and unplug the yellow 4-way connector to the inflator module, alongside the steering column.

Column shrouds: Remove the two screws retaining the top part of the shroud, and the four screws
retaining the lower part, and withdraw both parts from the column.

Instrument shroud: Pull the instrument shroud backwards to release the four spring clips from their
apertures in the dash panel.

Sill top trims: Release the two screws at the bottom of the coin pockets at the front of each sill, and pull
the sill top trim panels from the chassis.

Dash end panels: Release the two screws within the top of each coin pocket, and withdraw the switch
panel (driver's side) and blanking panel (passenger side) from the dash end panel. Unplug the wiring
harness from the switch panel.
From within the aperture, release the two screws retaining each end panel to the dash, and pull the panel
rearwards to withdraw the spring clips in the top of the panel from the dash.

Airbag door: Pull the airbag door away from the dash, which action will probably require the four retaining
clips to be renewed. Note that the door is constrained by two tether straps.

WARNING:

•

The only permitted repair to the airbag door and tether strap assembly is the replacement of the
plastic retaining clips which secure the door to the dashboard. If the clips are broken, they MUST
be replaced ONLY by the correct Lotus supplied parts. Do not attempt to fix the door in position
by any other means.

•

After SRS deployment, the airbag door assembly MUST be replaced even if there is no visible
damage.

Lotus Service Notes Section WD

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Centre vent panel and radio surround: Release the two screws at each side of the panel and withdraw.

Fascia top panel: Remove the 5 screws securing the rear edge of the panel to the dash rail, and withdraw
the panel rearwards to disengage the two spigots from the base of the windscreen surround. Disconnect
the speaker cables.

SDM: Unplug the harness connector from the SDM. Release the four retaining nuts, and withdraw the
sensor and diagnostic module from its mounting bracket.

Refitment of the SDM is a reversal of the removal procedure, but remember to check that the tether strap

bracket for the airbag trimmed door has been secured before the fascia top panel is fitted, and that new push
fasteners for the airbag door will be required.

WD.9 - DRIVER AIRBAG MODULE

WARNING: Safety precautions must be observed when handling a deployed airbag. After deploy-
ment, the airbag surface may contain a white packing powder used to ease deployment, together with
a small amount of sodium hydroxide dust, a by-product of the sodium azide reaction during deploy-
ment that can be irritating to the skin if left on for an extended period of time. Always wear gloves and
safety glasses when handling a deployed inflator module, and wash your hands with a mild soap and
water afterwards.

The driver's airbag (or inflator module) is housed in the hub of the steering wheel, beneath a moulded trim

cover designed to hinge open in the event of deployment. The module comprises:
-

an inflatable fabric bag;

an inflator (canister of gas generating material)

an initiator (or 'squib')
When the vehicle suffers a forward deceleration of sufficient magnitude to close both the safing sensor

and integrated accelerometer within the SDM, current flows through the deployment loop of both the driver and
passenger airbag module initiators and ignites the gas generating material. Each bag inflates in a fraction of a
second, the driver's bag bursting open the steering wheel centre trim cover, and then deflates via vents in the
bag, with the whole cycle taking less than one second. The airbag is designed for a single deployment, and
must then be renewed.

In order to help prevent unwanted deployment of the driver's airbag when servicing the steering column or

other SRS components, a shorting bar is incorporated in the airbag side of the 4-way harness connector plug
located alongside the steering column. The shorting bar operates when the connector is unplugged, to short
across the feed and return connections to the airbag. Thus, if a positive feed, or earth is inadvertently applied
to the connector terminals, both sides of the inflator module will be subject to the same electrical potential, and
no deployment will occur.

To replace driver's airbag

WARNING: The following procedures must be followed in the order listed to temporarily disable the
airbag system whilst working in the immediate vicinity of an airbag. Failure to follow this procedure
could cause unintended airbag deployment, resulting in personal injury and unnecessary airbag system
repairs.
a).

Turn off ignition.

b).

Disconnect the negative battery cable, and tape back to ensure that it cannot contact the battery terminal.

c).

From alongside the steering column, in the area of the column upper fixing, locate and disconnect the

driver's airbag yellow 4-way harness connector plug.

Column shrouds: Remove the two screws retaining the top part of the shroud, and the four screws
retaining the lower part, and withdraw both parts from the column.

On the reverse side of the steering wheel, locate and remove the two socket head screws, accessible via
holes in the plastic shroud around the steering wheel hub. Withdraw the airbag module and disconnect

Lotus Service Notes Section WD

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the yellow harness connector.

WARNING: When carrying a live airbag module, make sure the bag and trim cover are pointed away
from you. In case of an accidental deployment, the bag will then deploy with minimal chance of injury.
When placing a live airbag module on a bench or other surface, always face the bag and trim cover
upwards, away from the surface. This is necessary so that a free space is provided to allow the airbag
to expand in the unlikely event of accidental deployment.

If a driver's airbag is deployed, refer to steering section HG to determine whether the steering column
telescoping mechanism has been activated, and if necessary, renew the column assembly.

Mate the new airbag yellow connector plug with the harness plug in the steering wheel hub, and locate the
module into the steering wheel. Fit the two socket head retaining screws and tighten to 7Nm.

When all service work is complete, connect the harness plug alongside the steering column, and recon-
nect the battery. Turn on the ignition and check that the airbag tell tale lights for a few seconds and then
goes out.

WD.10 - ROTARY CONNECTOR

WARNING: The rotary connector MUST be replaced after SRS deployment even if there is no visible
damage.

The rotary connector is a device which fits between the steering wheel and column, and allows the

steering wheel to turn whilst maintaining electrical continuity to the airbag module and horn buttons. The
assembly consists of an annular housing fitted over the top end of the steering column, and containing a coil of
four wires. The wires are:
-

+ve feed to the inflator module (switched by the safing sensor);

ground to the inflator module (switched by the microprocessor accelerometer);

input to the horn buttons;

output from the horn buttons.
The steering column side of the device is fitted with a 4 way connector block which plugs into the SRS

harness. The steering wheel side of the device has two 2-way connector plugs, one for the airbag module, and
one for the horn buttons. The coil housing is constructed in two parts, with the outer part fixed to the outer
(stationary column, and the inner part keyed to the inner (rotating) column.

The two parts of the coil housing slide inside of each other in such a way as to allow the steering wheel

to be rotated through its full travel, lock to lock, whilst maintaining an unbroken feed to each of the four circuits
in the steering wheel hub, via the continuous wires in the coils.

In order to help prevent unwanted deployment of the air bag when servicing the steering column or other

SIR components, a shorting bar is incorporated in the rotary connector side of the 4-way SRS harness con-
nector plug. This shorting bar operates when the connector is unplugged, to short across the feed and return
connections to the inflator module. Thus, if a positive feed, or earth is inadvertently applied to the connector
terminals, both sides of the inflator module will be subject to the same potential, and no deployment will occur.

When servicing the rotary connector, it is most important that the correct orientation of the connector is

maintained on refitment, or the connector will run out of travel and be broken.

To replace the rotary connector
1.

Remove the airbag module from the steering wheel (see sub-section WD.8).

Disconnect the horn harness plug.

Bend back the locking tabs and release the nut securing the wheel to the column. Before attempting to
remove the wheel, ensure the front wheels are pointing straight ahead, and match mark the position of
the steering wheel hub against the column to aid re-assembly.

Using a suitable steering wheel puller tool, position the legs to reach through the holes in the wheel hub

Lotus Service Notes Section WD

Page 13

and bear directly against the hub, without interfering with the rotary connector. The centre screw should
bear against the end of the column. Withdraw the wheel/hub/rotary connector assembly from the column
splines.
Alternatively, for better puller access, the steering wheel can first be removed from the hub by releasing
the four retaining screws.
CAUTION: If excessive force is applied to either the wheel or column without an appropriate
puller, the telescoping mechanism of the outer column may be overridden, necessitating column
replacement.

Release the two countersunk screws retaining the rotary connector to the steering wheel hub.

On refitment, feed the airbag and horn connector plugs on the rotary connector through the hole in the
steering wheel hub, and secure the unit to the hub with the two countersunk screws. If necessary, refit the
steering wheel to the hub and secure with the four screws. Mate the horn buttons harness connector plug.

Before fitting the wheel/hub/rotary connector assembly to the column, the rotary connector must be
centralised: Turn the connector centre element fully counterclockwise until tight, then turn clockwise
approximately 2.5 turns until the arrow marks on the two parts of the rotary connector are aligned. Make
sure the front wheels are pointing straight ahead, and fit the assembly onto the column with the hub to
column match marks (made on disassembly) aligned, and engage the spring loaded pin on the column
switch housing with the slot in the rotary connector.

Fit a new locking tab washer, followed by the steering wheel nut, and torque tighten to 25 Nm (18.5 lbf.ft).
Bend up the locking tabs to secure.

Mate the airbag harness connector plug and fit the airbag module into the steering wheel. Retain with the
two socket head screws and tighten to 7Nm.

10.

Refit the column shrouds, and when all service work is complete, mate the horn/airbag connector to the
vehicle harness (clipping the connector to the column) and reconnect the battery. Check that the airbag
tell tale lights for a few seconds with ignition, and then goes out.

WD.11 - PASSENGER AIRBAG MODULE

The passenger's airbag (or inflator module) is housed within the passenger side of the fascia, mounted on

a bracket to the scuttle beam, and arranged to deploy via an aperture in the dash panel covered by a trimmed
'door'. The door is designed to break away in the event of airbag deployment, but is tethered to the dash by two
restraining straps. The airbag module comprises:
-

an inflatable fabric bag;

an inflator (canister of gas generating material)

an initiator (or 'squib')
When the vehicle suffers a forward deceleration of sufficient magnitude to close both the safing sensor

and integrated accelerometer within the SDM, current flows through the deployment loop of both the driver and
passenger airbag module initiators and ignites the gas generating material. Each bag inflates in a fraction of a
second, the passenger's bag bursting through the dash panel 'door', and then deflates via vents in the bag, with
the whole cycle taking less than one second. The airbag is designed for a single deployment, and must then be
renewed.

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