Lotus Evora - Sensor & Diagnostic Module (SDM)

Lotus Service Notes Section WF
Page 9
The tell tale will be activated without SDM intervention in the following situations:
• theminimumvoltageof8.0Vhasnotbeenexceededafterswitchingontheignition.
• theenergyreserve(inSDM)hasrunlow,whichmaybecausedbysupplyvoltagesbelow7.8V.
• thewatchdoghasinterfered.
A trouble code readout using tell tale blink codes is not implemented.
Power Supply & Grounding
The nominal supply voltage of +12 volts is derived from terminal 5 when the ignition is switched on. The
SDM internal ground (terminal 7) must be securely connected to the vehicle chassis ground. To provide redun-
dant grounding, the SDM housing is internally connected to the ground connector pin.
SupplyVoltageRange
The SDM is designed to operate within the following voltage ranges:
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 accel-
eration 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.
WF.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 in an alloy box bolted to the centre underside of the scuttle beam.
1. Follow the safety procedure detailed in sub-section WF.6 to turn off the ignition, disconnect the battery
and unplug the rotary connector.
2. From the footwells, release the 8 setscrews securing the SDM mounting box to the scuttle. Release the
three screws securing the SDM to the box and unplug the two harness connectors.
Refitment of the SDM is a reversal of the removal procedure, torque tightening the fixing screws for SDM
and mounting box to 9 Nm.