ASTON MARTIN DB7 1997 Workshop Manual

Electrics
Airbag System
Airbag DM Fault Code 41
Right hand crash sensor feed or return open circuit.
Airbag DM Fault Code 42
Left hand crash sensor feed or return open circuit.
Normal Operation
The diagnostic module constantly measures the
voltage at pins
1
-2 and
1-11.
The voltage should be
10±1 volt. The two wires are connected together
within the right hand crash sensor. If the voltage at
1-2 falls below that at 1-11, an open circuit has

occurred.
Fault code 41 will be declared and the
airbag lamp will be illuminated.
Normal Operation
The diagnostic module constantly measures the
voltage at pins
1
-6 and
1
-12.
The voltage should be
10±1 volt. The two wires are connected together
within the left hand crash sensor. If the voltage at
1
-
5 falls below that at 1-12, an open circuit has

occurred.
Fault code 42 will be declared and the
airbag lamp will be illuminated.
Possible Causes
• Open circuit in the wires from diagnostic module
pins
1
-2 or
1 -11
to the right hand crash sensor.
• An open circuit within the right hand crash
sensor across pins 1 and 2 of the sensor
connector.
Fault Analysis

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

2.
Disconnect the diagnostic module and check
continuity between pins 1-2 and 1-11.
If the resistance is significantly greater than OQ, go
to step 3.
If the circu it resistance
is
OQ.,
the
fau It
is intermittent.
Manipulate the harness, particularly in the area of
the sensor connector and the crash sensor harness
to bulkhead harness connector, to identify the
location of the open circuit. Service the circuit as
necessary.
3. Check the right hand crash sensor connector for
security and service the connector if necessary.
If the connector is secure, disconnect and check
continuity from pin 1 to pin 2 of the sensor.
If the resistance is
h igh
or
an
open circuit
is
detected,
replace the crash sensor.
If the sensor continuity is good (0^2), service the
crash sensor loom or bu Ikhead harness
as
necessary
to remove the high resistance or open circuit.

4.
With the airbag simulators in circuit and all
connectors in place, clear the code
41.
Switch off
and then on again to check that the airbag warning
lamp comes on at 'ignition on' and extinguishes
after approximately six seconds.
5. Switch off and rearm the airbags (6.4.21.4)
3.
Possible Causes
• Opencircuitinthewiresfromdiagnosticmodule
pins
1
-6 or
1
-12 to the left hand crash sensor.
• An open circuit within the left hand crash sensor
across pins 1 and 2 of the sensor connector.
Fault Analysis
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Disconnect the diagnostic module and check
continuity between pins 1-6 and 1-12.
If the resistance is significantly greater than OQ, go
to step 3.
If the circu it resistance
isO£2,
the fault is intermittent.
Manipulate the harness, particularly in the area of
the sensor connector and the crash sensor harness
to bulkhead harness connector, to identify the
location of the open circuit. Service the circuit as
necessary.
Check the left hand crash sensor connector for
security and service the connector if necessary.
If the connector is secure, disconnect and check
continuity from pin 1 to pin 2 of the sensor.
If the resistance is high or
an
open circuit is
detected,

replace the crash sensor.
If the sensor continuity is good (OQ), service the
crash sensor harness or bulkhead harness as
necessary to remove the high resistance or open
circuit.
With the airbag simulators in circuit and all
connectors in place, clear the code 42. Switch off
and then on again to check that the airbag warning
lamp comes on at 'ignition on' and extinguishes
after approximately six seconds.
Switch off and rearm the airbags (6.4.21.4).
September 1996 6-95

Electrics
Airbag System o
--i.
D^?
Airbag DM Fault Code 44
Right hand crash sensor incorrectly mounted.
Normal Operation
The diagnostic module constantly measures the
resistance between pins 2-8 (RH crash sensor
ground) and
1
-3 (airbag DM system ground). If the
resistance rises above 2Q, fault code 44 is declared
and the airbag warning lamp is illuminated.
Possible Causes
• Loose sensor mounting or an accumulation of
dirt or corrosion at the sensor mountings.
• An open circuit or loose wire from DM pin 2-8
to the sensor.
• An open circuit wire or loose rivet within the
sensor.
Fault Analysis
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Disconnect the diagnostic module and check
continuity between pins 1-3 and 2-8.
If the resistance is significantly greater than
OQ,,
go
to step 3.
Ifthe circuit resistance
is
OQ,thefault is intermittent.
Manipulate the harness, particularly in the area of
the sensor connector and the crash sensor harness
to bulkhead harness connector, to identify the
location of the open circuit. Service the circuit as
necessary.
Check the right hand crash sensor mounting for
security and corrosion.
If neither problem is evident, go to step 4.
If either problem is evident, remove, clean and
resecure the sensor. Reconnect the diagnostic
module. Switch on and clear the code 44. Switch
off and then on again to check that the airbag
warning lamp comes on at 'ignition on' and
extinguishes after approximately six seconds.

4.
Check the right hand crash sensor connector for
security and service the connector if necessary.
If the connector is secure, disconnect and check
continuity from pin 1 to pin 2 of the sensor.
Ifthe resistance is high or
an
open circuit isdetected,
replace the crash sensor. Go to step 5
If the sensor continuity is good (OQ), service the
crash sensor harness or bulkhead harness as
necessary to remove the high resistance or open
circuit. Go to step 5.
5. With the airbag simulators in circuit and all
connectors in place, clear the code 44. Switch off
and then on again to check that the airbag warning
lamp comes on at 'ignition on' and extinguishes
after approximately six seconds.
6. Switch off and rearm the airbags (6.4.21.4)
6-96 September 1996

"3^=2?
Electrics
Airbag System
Airbag DM Fault Code 45
Left hand crash sensor incorrectly mounted.
Normal Operation
The diagnostic module constantly measures the
resistance between pins2-9 (LH crash sensor ground)
and
1
-3 (airbag DM system ground). If the resistance
rises above 2£2, fault code 45 is declared and the
airbag warning lamp is illuminated.
Possible Causes
• Loose sensor mounting or an accumulation of
dirt or corrosion at the sensor mountings.
• An open circuit or loose wire from DM pin 2-9
to the sensor.
• An open circuit wire or loose rivet within the
sensor.
Fault Analysis

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

2.
Disconnect the diagnostic module and check
continuity between pins 1-3 and 2-9.
If the resistance is significantly greater than OQ, go
to step 3.
If thecircuit resistance
is
OQ,
the fault is intermittent.
Manipulate the harness, particularly in the area of
the sensor connector and the crash sensor harness
to bulkhead harness connector, to identify the
location of the open circuit. Service the circuit as
necessary.
3. Check the left hand crash sensor mounting for
security and corrosion.
If neither problem is evident, go to step 4.
If either problem is evident, remove, clean and
resecure the sensor. Reconnect the diagnostic
module. Switch on and clear the code 45. Switch
off and then on again to check that the airbag
warning lamp comes on at 'ignition on' and
extinguishes after approximately six seconds.

4.
Check the left hand crash sensor connector for
security and service the connector if necessary.
If the connector is secure, disconnect and check
continuity from pin 1 to pin 2 of the sensor.
If the resistance is high or
an
open circuit isdetected,
replace the crash sensor. Go to step 5
If the sensor continuity is good (OQ), service the
crash sensor harness or bulkhead harness as
necessary to remove the high resistance or open
circuit. Goto step 5.
5. With the airbag simulators in circuit and all
connectors in place, clear the code 45. Switch off
and then on again to check that the airbag warning
lamp comes on at 'ignition on' and extinguishes
after approximately six seconds.
6. Switch off and rearm the airbags (6.4.21.4)
September 1996 6-97

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.
rrj ^
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

Etectrics
Seat Belt Pretensioner
Seat Belt Pretensioner Circuits
Seat Belt
Pretensioner
Module
1 o
2 O-
3 O
4 O
5 o
6o
70
80
9 O
10 o
n o-
12 O-
13o
14 O-
15 O-
Ground
c
r-1 B
> Warning
Lamp
'' Shorting
YK 2 Plug
Connector
Shorting
Links
/
/ PW
BW
3
1
O
2 1 (
LGS 1
3
YK
2
Instrument
Pack
, PCB
Squib

)

Lower
OBDII
^ Diagnostic
Socket
Air bag
* Diagnostic
Monitor
6-104 September 1996