1997 ASTON MARTIN DB7 airbag

Electrics
Airbag System ^?
Airbag DM Fault Code 51
Airbag diagnostic module - thermal fuse blown.
WARNING: The diagnostic module will blow the
internal fuse whenever a short circuit to ground
occurs in the deployment circuits. Itdoesnotblow
because of
excessive
current
flow.
The thermal
fuse is not a serviceable item. No attempt should
be made to replace or
bypass
the fuse.
WARNING: Do not install a new diagnostic
module until the short has been located and
corrected. A short which goes away before
corrective action has been taken must be regarded
asan intermittentfault. Installinga newdiagnostic
module when there is an intermittent fault will
result in repeated diagnostic module failures and
repeated repairs.
Fault Analysis
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Inspecttheconnectorsandterminalsfor any foreign
metal objects or damaged terminals which could
be the cause of the short circuit.
Check each of the circuits in the possible causes list
and isolate the intermittent short circuit. Rectify the
fault.
See the warnings above about replacement of
diagnostic modules when intermittent shorts are
present.
Replace the diagnostic module.
Reconnect all components and rearm the airbags
(6.4.21.4).
Normal Operation
In order to prevent airbag deployment in the event
of a short circuit to ground, the diagnostic module
blows its internal fuse as soon as a short to ground
is detected. This action removes all battery and
back-up power from the deployment circuits. The
diagnostic module will flag the higher priority
codes 13 or 14 while the short to ground exists. If
the short is intermittent and temporarily corrects
itself, the d iagnostic modu le wi
11
flag code
51.
If the
short to ground returns, the diagnostic module will
again flag the higher priority code 13 or 14 instead
of code 51.
Code 51 after Airbag Deployment
The internal wiring may be shorted to the metal
airbag housings after the airbags are deployed. The
diagnostic module will see this as a short to ground
in the deployment wiring, it will flagacode 14and
blow the internal fuse. As the deployed airbags

cool,
the short circuit may rectify itself. The
diagnostic module will then flag a code 51. This
intermittentfault must be investigated and corrected.
Possible Causes
A short circuit to ground in any of the following:
DM pins 2-2, 2-5 or 2-6 to the safing sensor
DM pins 2-2, 2-5 or 2-3 to the passenger airbag
DM pins 2-2, 2-4 or 2-5 to the drivers airbag
DM pins
1
-2 or
1 -11
to RH crash sensor
DM pins
1
-6 or
1
-12 to LH crash sensor
6-98 September 1996

in:[M3^?
Electrics
Airbag System
Airbag DM Fault Code 52
Back-up power supply - voltage boost fault.
Normal Operation
A back-up power supply consisting of a capacitor
and voltage booster is contained within the
diagnostic module. The voltage booster charges
the capacitor to 24 ±
1
volt when the ignition is on.
The back-up power supply is connected to
diagnostic module pin 1-9 via a diode. Since the
resistance of pin 1-9 to ground is infinite, the
capacitor has no discharge path and the back-up
supply
is
maintained ata high
voltage.
Thediagnostic
module monitors this voltage and will flag a code
52 if a minimum of 23V is not achieved within 45
seconds of switching on the ignition.
Possible Causes
Low back-up supply voltage may be caused by:
• Partial or total short circuit of pin 1-9 to ground.
• Boost circuit failure within the diagnostic
module.
Fault Analysis

1.
Disarm the airbag system and fit airbag simulators
(6.4.21.4).

2.
Disconnect the diagnostic module. Check for a
partial or permanent short circuit to ground from
diagnostic module harness connector pin 1-9.
If no short circuit is detected, go to step 3.
If a short circuit is detected, service the wiring as
necessary. Reconnectthediagnostic module. Clear
the code 52. Rearm the airbags.
3. Using a high resistance digital multimeter, set up to
measure the voltage from diagnostic module pin
1
-
9 to ground. Switch on the ignition.
If the voltage is in the range 24 ± 1 volt, the back­
up power supply is good. Suspect an intermittent
short circuit to ground and recheck the output
circuit from pin 1-9.
Ifthe voltage is below the range 24 ±
1
volt, replace
the diagnostic module.

4.
Rearm the airbags (6.4.21.4).
Airbag DM Fault Code 53
internal diagnostic module failure.
Normal Operation
The diagnostic module constantly measures the
voltage on pins
1
-2,
1
-6,
1 -11
and
1
-12. It should
be 10
±1
volt. The voltage is regulated by a resistor
within the diagnostic module and the resistance to
ground ofpins
1-2,6,11
and 12 should be infinite.
The resistance across the normally open contacts of
the crash sensors should also be infinite. If the
resistance of the pins to ground or across the crash
sensors becomes measurable, the voltage wi
11
drop.
At between 5V and lOVthe diagnostic module will
recognise an internal voltage regulation failure and
flag a code 53 fault and the airbag warning light will
be illuminated.
Notes: A dead short to ground in the
crash
sensor circuits
will drop the voltage below 5V and the diagnostic
module will flag
a
code
14
fault.

The
diagnostic module
performs several self-tests as
the
ignition is switched on. If it fails any
test,
fault code 53
will be flagged.
Possible Causes
• A decrease in resistance from infinity between
the primary crash sensor circuits and ground.
• An internal diagnostic module self-test failure.
Fault Analysis

1.
Disarm the airbag system and fit airbag simulators
(6.4.21.4).

2.
Check each of pins 1-2, 1-6, 1-11 and 1-12 for
continuity to ground.
If resistance of all circuits is infinity, go to step 3.
If any resistance other than infinity is detected,
service the circuit wiring as necessary. Reconnect
all connectors and switch on and clear all fault
codes.
Switch off the ignition and then switch on again.
Check that the airbag warning lamp comes on at
'ignition on' and extinguishes after approximately
six seconds on satisfactory completion of the airbag
system self-check.
3. Rearm the airbags (6.4.21.4).
September 1996 6-99

Electrics
Airbag System [n:M^^^?
Airbag DM Fault Code 99
Rapid continuous flashing of the airbag warning
light - Both front crash sensors disconnected.
Normal Operation
Each crash sensor has three wires. Two deploy the
airbag and monitor the sensors connection to the
diagnostic monitor. The third wire monitors the
mounting of the sensor to the vehicle bodywork. A
code99isdeclaredifbothsensorsaredisconnected
and not properly grounded.
Fault Analysis
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Check continuity of all circuits listed below and
service as necessary.
LH Crash Sensor
DM Pin
1-6
1-12
2-9
RH Crash Sensor
DM Pin
1-2
1-11
2-8
Sensor Pin
1
2
4
Sensor Pin
1
2
4
Also check for correct grounding of the diagnostic
module and the sensor cases.
Reconnect all connectors, clear fault code 99.
Switch off the ignition and then switch on again.
Check that the airbag warning lamp comes on at
'ignition on' and extinguishes after approximately
six seconds on satisfactory completion of the airbag
system self-check.
Rearm the airbags (6.4.21.4).
6-100 September 1996

5^^?
Electrics
Seat Belt Pretensioner
The Seat Belt Pretensioner System (where fitted)
Description
The DB7 seat belt pretensioner system operates the drivers seat belt pretensioner in conjunction with the Airbag

system.
The seat belt pretensioner control module is located under the right hand seat, beside the right hand seat
control module.
The pretensioner control module calculates changes in vehicle speed using an input signal from an accelerometer.
When a collision is detected (Rapid reduction in vehicle speed) and the safing sensor in the airbag system is also

activated,
the pretensioner charge
is
fi red usingelectrical energy stored in a capacitor within the pretensioner control
module. Firing of the pretensioner charge applies additional tension to the drivers seat belt.
The airbag and seat belt pretensioner systems share the SRS (Airbag) warning lamp. Any fault detected by the
pretensioner control module is indicated by constant illumination ofthe
SRS
(Airbag) warning lamp. Flashing of the
SRS warning lamp indicates a fault in the airbag system.
Should both systems develop faults, the pretensioner system will permanently illuminate the warning lamp. This
would mask the airbag system warning indication. Therefore, rectify the pretensioner fault and then retest for faults
in the airbag system
The pretensioner control module can log up to 10 diagnostic trouble codes together with a time since each fault was
alerted to the driver. Each
fau It
wi
11
be identified as 'Permanent' or 'Intermittent' on the PDU diagnostic trouble codes

screen.

System Connections
DB7 is fitted with an Autoliv ECS or RC5 Pretensioner Control Module. The Pretensioner Control Module has an 18
pin connector featuring six shorting bridges. The mating halves of the connector may be securely locked using a
double mechanical locking system.
The following pins on the control module connector are used in the Aston Martin seat belt pretensioner system:
Pin 1 Ground
' ' "L Pin 2 Airbag Warning Lamp
Pin 11 Drivers airbag positive
Pin 12 Drivers airbag negative
Pin 14 Serial communications
Pin 15 12 volt positive feed
Case Ground

15.
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ooooooooooooooo
16 illn
^
Note: Pins
1
-2, 3 -4, 5 -6, 7 -8,9 -
10
and 11-12
are
shorted
together
by internal shorting links within the connector when
it
is
disconnected.
The
short circuits may
be
temporarily
overcome
for fault analysis
purposes
by inserting
a
suitable non-metallic

cheater
(the
sBfTiG
size
3s
the
p€gs
in the controller connector) into the rectsngul^r hole opposite the relevsnt p3ir of pins.
September 1996 6-101

Electrics //—>> ^^^^^^ • >^
Seat Belt Pretensioner I'•—
-"i-t.
^-^
JH—X

System Fault Strategy
No single fault may cause an unexpected deployment. The controller will supervise the pretensioner electrical
system in order to warn the driver should a fault occur. Any fault detected by the self diagnostics shall cause the SRS/
airbag warning lamp to be activated, and in some cases the pretensioner control module to enter shutdown mode.
In shutdown mode, the energy of the reserve capacitors shall be discharged to avoid unintended deployment.
As the ignition is switched on, the pretensioner controller will directly discharge the energy capacitors. When the
start up procedure is completed without detecting any faults, the DC/DC converter will be activated allowing the
capacitors to be charged. The system shall be fully active within
11
secondsafterswitchingthe ignition on providing
that no faults are detected.
All system faults monitored by the controller are filtered in software to avoid fault warnings due to transient electrical
disturbances.
If a fault which could lead to inadvertent deployment is detected by the microprocessor, a software shutdown will
be generated. However, a leakage to an earth or positive potential in the pretensioner output circuit shall not cause
the controller to enter shutdown mode.
If a permanent short of the ignition transistor occurs, a shutdown shall be generated by the hardware circuit. If a
shutdown occurs, the system shall be unable to deploy the pretensioner after a period of 3 seconds (i.e. capacitors
discharged to under minimum deployment voltage).
WARNING: To avoid the possibility of personal injury caused by accidental deployment of the pretensioner,
disconnect the vehicle battery and wait at least 10 minutes for all voltages to fully discharge before working on
the pretensioner
system.
This
covers the possibility of the normal capacitor discharge circuits being inoperative
and failing to discharge the capacitor when instructed to do so.
WA RNING: Do not make any electrical measurements on the pretensioner squib. Electrical measurement devices
can induce sufficient voltage to cause unintentional firing of the pretensioner assembly
If the module enters shutdown mode, all diagnostic functions are stopped, but the communications link remains

active.
A fault code corresponding to the cause of the problem may be read by the PDU.
Assembly/Removal/Service I nstructions
WARNING: In the event of a vehicle impact where the airbags and the seatbelt pretensioner (if fitted) are
deployed, the following actions MUST be performed:
Check the condition of the
seatbelts,
steering wheel, steering column, all connections to airbags, and the column
switchgear connectors for integrity and damage. If in any doubt, replace suspected parts for new parts.
Replace both crash
sensors,
the safing sensor and the seatbelt pretensioner module (if fitted).
On completion of all repair procedures, switch on the ignition and check that the Airbag/SRS warning light
comes

on when the ignition is switched on and extinguishes after approximately six seconds indicating satisfactory
completion of the airbag and pretensioner
system
self
tests.

Vehicles for the North American, Australian and Japanese markets are fitted with drivers seat belt pretensioner
systems and are fitted with a shorting plug in the yellow connector adjacent to the pretensioner control module.
Vehicles for other markets do not have drivers seat belt pretensioners fitted but have a blanking plug in the yellow
connector adjacent to the pretensioner control module.
6-102 September 1996

'^^
Electrics
Seat Belt Pretensioner

6.6.26.1
Pretensioner Control Module -
Renew
Read the warnings given in system fault strategy
and service instructions on the previous page before
starting the following procedure.
Procedure

1.
Disconnect the battery ground (black) lead and
wait at least 10 minutes for the pretensioner power
supply to fully discharge before working on the
pretensioner system.
Note:
The
vehicle battery must
be
disconnected within
12
seconds
of switching off
the
ignition to avoid the alarm
siren sounding.
2. Motor the right front seat to its rearmost position.
3. Remove the floor carpet and the ECU cover.

4.
Disconnect the pretensioner control module
connector (orange connector with black safety

clip).

5. Remove 3 flange screws securing the module,
noting the position of the earth strap.
6. Fit the new pretensioner control module with the
connector facing to the rear and secure with 3
flange screwsensuringthatthe earth strap is secured
with the outboard rear screw.
7. Connect the orange connector to the control
module.
8. RefitandsecuretheECU cover and the floor carpet.
9. Reconnect the battery ground (black)
lead.

Note:
The
vehicle clock and the window control unit will
need
resetting
after completion of this procedure.

10.
Switch on the ignition and check that the airbag
warni ng I ight comes on when the ign ition
is
switched
on and extinguishesafterapproximately sixseconds
indicating satisfactory completion of the
pretensioner and airbag system self tests.

6.6.24.1
Pretensioner Assembly Renew
Read the warnings given in system fault strategy
and service i nstruaions on the previous page before
starting the following procedure.

1.

2.

4.

Procedure
Motor the drivers seat to its rearmost position.
Disconnect the battery ground (black) lead and
wait at least 10 minutes for the pretensioner power
supply to fully discharge before working on the
pretensioner system.
Note: Disconnect the battery within 12 seconds of
switchingoffthe ignition to avoid the alarm siren sounding.
Remove the pretensioner trim cover. Unbolt the
drivers seat. Tip the seat rearwards and disconnect
the seat and pretensioner squib connectors.
Release one bolt at the
base
of the seat belt
stal k
and
remove the pretensioner assembly.
Ensure that the safety clip is fitted to the connector
at the pretensioner squib. Fit the new assembly,
locating the anti-rotation peg into the rear hole of
the mounting bracket. Secure the assembly with
one bolt. Torque the bolt to 35Nm.
Safety Clip in place
5. Route the pretensioner lead between the seat and
the frame. Reconnect the seat and pretensioner
connectors. Ensure that the pretensioner connector
safety clip is secured. Refit the drivers seat and
loosely secure.
6. Reconnect the battery ground (black)
lead.

Note:
The
vehicle clock and
the
window control unit will
need
resetting
after completion of this procedure.
7. Switch on the ignition and check that the airbag
warn i ng I ight comes on when the ignition
is
switched
on and extingu
ishes
after approximately six seconds
indicating satisfactory completion of the
pretensioner and airbag system self tests.
8. Fit the front screws ensuring a 1.2mm gap between
screws and slide. Power the seat forwardTorque the
rear screws to 25 Nm. Power the seat backward.
Torque the front screws to 25 Nm.
September 1996 6-103

Electrics
Seat Belt Pretensioner ^?
060C Warning Lamp Short Circuit
060C will be logged if the nnonitor current flow
through the SRS/Airbag warning lamp is excessive.
The warning lamp circuit is normally at 12 volts and
is switched to ground by the airbag control module
or by the pretensioner control module when one of
these control modules detects a fault.
If either control module connector is displaced and
the ignition is switched on, the warning lamp will
be illuminated via the ground shorting link between

pins!
and 2 ofthe pretensioner controller connector
or pins 4 and 5 of the airbag controller connector,
both control modules must be checked for the
appropriate DTC to isolate which circuit is at fault.
Procedure

1.
Connect the PDU to the lower diagnostic socket
and access the pretensioner control module. Verify
that an 060C code is logged and note if the fault is
shown as intermittent. Note any other codes in the
DTC log and then clear all codes. Go to step 2.
If fault code 060C is not logged, go to the diagnostics
section of the airbag system.

2.
Check the security of the pretensioner control
module connector.
If the connector is secure, go to step 3.
If the connector isdisplaced,resecu re theconnector.
Clear all logged DTCs and retest the vehicle to
ensure that the problem is resolved.
3. Access the SRS/Airbag warning lamp and check the
lamp resistance.
If the resistance is approximately
120£2,
the lamp is

good.
Refit the lamp and go to step 4.
If the resistance of the lamp is significantly less than
approximately 120^, fit a new lamp and refit the
instrument panel. Clear the logged DTCs from the
pretensioner control module and retest the vehicle
to ensure that the problem is resolved.

4.
If the checks in step 3 are good, the low circuit
resistance must be in the instrument pack or in the
control module. Replace the pretensioner control
module and reconnect all components.
6. Switch on the ignition and then test the vehicle.
If the 060C code is logged again, replace the
instrument pack.
060D Warning lamp open circuit
060D will be logged if the monitor current flow
through the SRS/Airbag warning lamp is below the
normal monitor level.
The warning lampcircuit is normally at 12 voltsand
is switched to ground by the airbag control module
or by the pretensioner control module when one of
these control modules detects a fault.
Procedure
Connect the PDU to the lower diagnostic socket
and access the pretensioner control module. Verify
that an 060D code is logged and note if the fault is
shown as intermittent. Note any other codes in the
DTC log and then clear all codes. Go to step 2.
lffaultcode060D is not
logged,
gotothediagnostics
section of the airbag system.
Switch off the ignition. Access the SRS/Airbag
warning lamp and check the lamp resistance. The
resistance should be approximately 120Q.
If the resistance is 120i2, go to step 3.
If the lamp resistance is significantly lower than

120^2,
replace the lamp. Retest the vehicle to
ensure that the problem is resolved.
Wait 10 minutes after switching off the ignition to
ensure that the pretensioner firing capacitors have
fully discharged.
Disconnect the pretensioner control module and
temporarily cheat the warning lamp shorting link.
Note: The control module harness connector has a
shorting link which short circuits the warning lamp line
(pin 2)to ground
(pin
Dwhen
the
connector
is
displaced.
Carefully insert a suitable non-metallic cheater to remove
the
short
circuit
between
pins
1
and 2 before continuing
with fault
diagnosis.

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i^i
^ ^ ^ 1^1
Insert cheater hare
6-108
September
1996

Electrics
Seat Control Module Removal/Replacement 97.5 MY 'O "3^2?
Switch on the ignition and checi< that the airbag
warning lamp comes on when the ignition is
switched on and extinguishes after approximately
six seconds indicating satisfactory completion of
the pretensioner and airbag system self
tests.

Fit
the front
seat
retaining screws ensuring
a
1.2mm
gap between the screw heads
and
the
slides.
Power
the seat forward and refit the rear screws.
Caution:
Centralise the
rear
fixing holes
with the
body weld
nuts
prior to
inserting the
bolts.

Torque the rear screws to 25 Nm. Power the seat
backwards. Torque the front screws to 25 Nm.
Motor the seat through its full range of movement
to ensure correct
operation.

6.6.08
Seat Control Module 97.5 MY
Removal
WARNING -
Seat
belt
Pretensioners
(if
fitted):

To avoid the possibility
of
personal injury caused

by accidental deployment of the seat belt

pretensioner,
disconnect
the
vehicle battery and

wait at
least
10
minutes
for all
voltages
to fully

discharge
before
working
near the
pretensioner

system.
This covers
the
possibility
of
the
normal
capacitor
discharge circuits
being
inoperative and
failing to discharge the detonator capacitor when
instructed
to
do
so.

1.
Lower the door window and open the relevant
door. Disconnect
the
battery ground cableand wait
for 10 minutes if
a
pretensioner
is
fitted.
Otherwise,
proceed immediately to step 2.
(ei-SMiECu
Figure!.
Seat ECU Removal

2. Loosen two nuts securing the seat ECU. Slide the
ECU to the left and remove it from the front of the
seat.
3. Disconnect two connectors from the ECU.
Replacement

1.
Reconnect the two control module connectors. Fit

the seat control
moduleand
tighten
thetwo securing

nuts.

3. Reconnect the battery ground and test for correct
operation of the seat controls.
6-128 April 1997