Continuous Airbag Warning Lamp - Aston Martin DB7 Workshop Manual

Electrics
Airbag System
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Continuous Airbag Warning Lamp
Inoperative lamp circuit or no ignition supply to the
airbag diagnostic module.
Normal Operation
The airbag warning lamp is designed to illuminate
for approximately six seconds when the ignition is
switched on. This period isallocated for satisfactory
performance of the airbag system self test. If after
this period, the diagnostic module detects a fault
within the system, the airbag warning lamp w i l l
begin to flash.
Note: The seat belt pretensioner system (if fitted) shares
the airbag/SRS warning lamp with the airbag system. If a
seat belt pretensioner fault is detected, the Airbag/SRS
warning lamp will be permanently illuminated. Ensure
thata permanently lit lamp is nottheresultof a pretensioner
fault before carrying out fault analysis on the airbag
system.
Poor connection or disconnection of the diagnostic
module harness may cause a short circuit from D M
pin 4 (warning lamp control) to pin 5 (ground) and
cause permanent illumination ofthe warning lamp.
Faulty operation of the diagnostic module internal
logic may fail to turn off the warning lamp control
circuit and cause constant illumination of the
warning lamp.
Fault Analysis
WARNING: Read and adhere to all warnings and
safety procedures at the start of this section when
working on the airbag system.
1. Disarm the airbag system and fit airbag simulators
(6.4.21.4). Reconnect the battery.
2. Inspectthe instrument pack and diagnostic module
connectors for damaged, pushed out pins, proper
location etc.
If any defects are identified, service as necessary.
Retest to ensure correct operation of the airbag
warning light.
If the connector condition and security are good,
reconnect the connectors and go to step 3.
5.
Connect the PDU to the upper diagnostic socket
and monitorthe airbag warning lamp signal. Switch
on the ignition.
If the signal is permanently low, suspect a short
circuit to ground on the airbag warning lamp
control line within the diagnostic module or from
diagnostic module pin 1 -4 to earth. Co to step 4 .
If the signal switches low for six seconds after
ignition on but the airbag warning lamp is
permanently illuminated, suspect a fault in the
output side of the instrument pack to the airbag
warning lamp.
Disconnect diagnostic module plug 1 (slate) and
withdraw the plastic locking wedge to prevent
shorts to other circuits. Check continuity from pin
1-1 to ground.
If a short circuit to ground is detected, service the
wiring as necessary. Replacethe locking wedge, re-
insert the connector. Switch on the ignition and
check that the airbag warning lamp signal atpin 1-
4 goes high six seconds after switching on the
ignition and that the warning lamp extinguishes.
If no short circuitto ground isdetected,thediagnostic
module is faulty. Replace the diagnostic module.
Switch on the ignition and check that the airbag
warning lamp signal at pin 1 -4 goes high six seconds
after switching on the ignition and that the warning
lamp extinguishes.
Switch off the ignition. Disconnect the battery.
Rearm the airbags (6.4.21.4). Switch on the ign ition
and check for correct indications from the airbag
warning lamp.
6-84 September 1996