1997 ASTON MARTIN DB7 airbag

Electrics
Airbag System =2?
Airbag DM Fault Code 24
Safing sensor output - battery feed/return open
circuit.
Normal Operation
The diagnostic module measures the voltage on
diagnostic module pins 2-5 and 2-6 the voltage
varies with the vehicle charge level
as
shown in the
table below:
in 2-5
2.3V
2.4 V
2.5V
2.7V
2.8V
3.0V
3.1V
3.2V
3.4V
3.5V
3.7V
3.8V
4.0V
4.1V
4.3V
Pin 2-6
2.3V
2.4V
2.5V
2.7V
2.8V
3.0V
3.1V
3.2V
3.4V
3.5V
3.7V
3.8V
4.0V
4.1V
4.3V
Cliarge Volts
9.0V
9.5V
10.0V
10.5V
11.0V
11.5V
12.0V
12.5V
13.0V
13.5V
14.0V
14.5V
15.0V
15.5V
16.0V
The diagnostic module also measures the voltage at
pin 1-7 (battery input). Using the battery input
voltage, the system can predict the expected voltage
level on pins 2-5 and 2-6. If the voltage on pins 2-
5 or 2-6 is higher or lower than expected, a fault
code 24 will be declared.
Possible Causes
• Open circuit or high resistance in the wiring
harness or safing sensor.
• Intermittent battery voltage on pin 1-7
• The resistance of the pin 2-5 to 2-6 circuit to

ground.
This circuit should be open to ground at
all times.
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).

2.
Probe the battery input voltage terminal
1
-7. Start
the engine and monitor the charge voltage level
using a digital multimeter. Run the engine at idle
speed and look for any instability in the voltage

level.
Run the engine at a constant medium speed
and then at a constant high speed and repeat the
observation for voltage instability.
If the voltage levels are stable, go to step 3.
If instability of the voltage level is observed,
Investigate and rectify the problem in the charging
circuit.
3. Switch off the ignition. Disconnect the diagnostic
module and check for OQ continuity from pins 2-5
to 2-6.
If no resistance is detected, go to step 4.
If any resistance is detected between pins 2-5 and

2-6,
service the wiring or safing sensor to achieve
Ofi continuity.

4.
Measure the resistance to ground from pins 2-5 and

2-6.

If no short circuit is detected, replace the diagnostic
monitor. Rearm the airbags (6.4.21.4).
If
a
short to grou
nd
is detected, service the wiring or
safing sensor as necessary. Rearm the airbags
(6.4.21.4).
6-90 September 1996

o; D^?
Electrics
Airbag System
Airbag DM Fault Code 32
Drivers airbagcircuit high resistance or open circuit.
Normal Operation
The diagnostic module measures the resistance
across pins 2-4 and 2-5 every time the ignition is
switched on. The resistance should be 1.6 to
1.8£2.

This value is made up of the airbag
1
.OQ and the
cable reel cassette windings 0.3-0.4Q per winding.
If the total resistance in the drivers airbag circuit
exceeds 4.0^, fault code 32 will be declared and
the airbag lamp will be illuminated.
Note: The
resistance
of
the airbag simulator is
2.5Q,

therefore expect total resistance readings
of 2.8 - 2.9Q
with
the simulator
fitted.

Caution: The drivers airbag and the cable reel
cassette connectors contains shorting bars which
short circuit pins 1 and 3 of the connectors when
disconnected.
DO NOT REMOVE THE AIRBAG SHORTING
BAR

UNDER ANY CIRCUMSTANCES.
The harness shorting bars may be temporarily
removed during the following resistance checks.
Possible Causes
• Excessive resistance in the cable reel cassette
connections.
• Open circuitor high resistance in the cable reel
cassette windings.
• Open circuit or high resistance in the wiring
harness
• Open circuit or high resistance in the drivers
airbag module.
• Defective diagnostic module.
WARNING: Do not attempt a direct resistance
check on the airbag module. Accidental
deployment can occur due to the induced voltage
from the measuring equipment.
3.
Fault Analysis
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Disconnect the diagnostic module and remove the
plastic wedge from connector 2 (black). Measure
the resistance between pins 2-4 and 2-5. The
resistance should be 2.8 - 2.9Q.
If the resistance is 2.8 - 2.9Q, go to step 3.
if the resistance is not in the range 2.8 - 2.9D, isolate
the continuity problem noting the following:
a) Pin 2-4 is shorted to pin 2-5 by a shorting link
. when plug 2 of the diagnostic connector is

removed.
Removal of the plastic wedge from
the plug will remove the short circuit.
b) Both halves of the cable reel conneaor have
shorting links which will short pin 1 to pin 3
when the connection is removed. Removal of
the plastic wedge horn either half will remove
the short circuit in that part of the wiring.
c) A shorting link is fitted in the airbag module
connector. Do not attempt to remove this
shorting link or the plastic wedge. Do not
attempt to measure the resistance of the airbag
module.
d) Carefully replace all plastic wedges on
completion of the circuit checks.
The fault is therefore in either the airbag module or
in the airbag diagnostic module.
Substitute a known good diagnostic module. If
code 32 recurs with the airbag simulator fitted,
there is a fault in the wiring.
If the fau
It
code 32 does not recur, rearm the airbags
(6.4.21.4) and retest.
If fau
It
code 32 recu
rs
with the ai rbag modu
le
fitted,
the airbag module is faulty. Replace the drivers
airbag module (4.5.01.3).
September 1996 6-91

Electrics
Airbag System ^^2?
Airbag DM Fault Code 33
Passengers airbag circuit high resistance or open
circuit.
Normal Operation
The diagnostic module measures the resistance
across pins 2-2 and 2-3 every time the ignition is
switched on. The resistance should be 0.9 to 1.1Q.
If the total resistance in the passengers airbag
circuit exceeds 4.0Q, fault code 33 will be declared
and the airbag lamp will be illuminated.
Note:
The
nominal
resistance
of the airbag simulator
is

2.5£2,
therefore
expect
a
total circuitresistancereadingof
2.4 - 2.6Q with the simulator
fitted.

Caution: The passenger airbag connector contains
shorting bars which short circuit pins 1 and 3 of
both sides of the connector when disconnected.
DO NOT REMOVE THE AIRBAG SHORTING
BAR

UNDER ANY CIRCUMSTANCES.
The harness shorting bar may be temporarily
removed during the following resistance checks.
Possible Causes
• Open circuit or high resistance in the wiring
harness
• Open circuit or high resistance in the passenger
airbag module.
• Defective diagnostic module
WARNING: Do not attempt a direct resistance
check on the airbag module. Accidental
deployment can occur due to the induced voltage
from the measuring equipment.
Fault Analysis

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

2.
Disconnectthediagnostic module and remove the
plastic wedge from connector 2 (black). Measure
the resistance between pins 2-2 and 2-3. The
resistance should be 2.4 - 2.6Q.
if the resistance is 2.4 - 2.6Q, go to step 3.
Ifthe resistance is not in the range 2.4-2.6S2, isolate
the continuity problem noting the following:
a) In the diagnostic module connector, pin 2-2 is
shorted to pin 2-3 by a shorting link when plug
2 of the diagnostic connector is removed.
Removal of the plastic wedge from the plug wi
11

remove this short circuit.
b) At the airbag module harness connector, pin 1
is shorted to pin 3 when the airbag is
disconnected. Removal of the plastic wedge
from the plug will remove this short circuit.
c) The shorting link fitted in the airbag module
connector will short pin 1 to pin 3 when the
airbag is disconnected. Do not attempt to
remove
this
shorting link or the plastic wedge.
Do not attempt
to
measure the resistance of the
airbag module.
c) Carefully replace all plastic wedges on
completion of the circuit checks.
3. The fault is therefore in either the airbag module or
in the airbag diagnostic module.
Substitute a known good diagnostic module. If
code 33 recurs with the airbag simulator fitted,
there is still a fault in the wiring or the simulator.
Ifthe fault code 33 does not recur, rearm the airbags
(6.4.21.4) and retest.
If fault code 33 recurs with the airbag module fitted,
the airbag module is faulty. Replace the passengers
airbag module (7.8.02.6).
6-92 September 1996

in:m3'^?
Electrics
Airbag System
Airbag DM Fault Code 34
Drivers airbag circuit low resistance or short circuit.
Normal Operation
The diagnostic module measures the resistance
across pins 2-5 and 2-4 every time the ignition is
switched on. The resistance should be 1.6 to 1.8Q.
This value is made up of the airbag
1
.OQ and the
cable reel cassette windings 0.3-0.4£2 per winding.
If the total resistance in the passengers airbag
circuit falls below 0.7Q, fault code 34 will be
declared and the airbag lamp will be illuminated.
Note: The nominal
resistance
of the airbag simulator is
2.5Q, therefore expect
a
total circuit resistance readingof
3.1 -
3.3£2
with the simulator
fitted.

Caution: The drivers airbag connector contains
shorting bars which short circuit pins 1 and 3 of
both sides of the connector when disconnected.
DO NOT REMOVE THE AIRBAC CONNECTOR
SHORTING BAR UNDER ANY CIRCUMSTANCES.
The airbag harness shorting bar may be temporarily
disabled during the following resistance checks.
Possible Causes
• Poorly mated cable reel cassette connector. If
the connector is poorly mated, the shorting bars
may not be fully retracted.
• Faulty shorting bar may short circuit 2-4 and 2-
5 together.
• Short circuit in the cable reel cassette windings.
• A short across the airbag terminals in the airbag
module.
Fault Analysis
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Disconnect the diagnostic module and remove the
plastic wedge from connector 2 (black). Measure
the resistance between pins 2-5 and 2-4. The
resistance should be 3.1 - 3.3Q.
If the resistance is 3.1 to 3.3Q, go to step 4.
If the resistance is below 3.1 - 3.3Q, go to step 3.
Disconnect the cable reel cassette connector at the
steering column and remove the plastic wedge.
Measure the resistance from pins 2-4 and 2-5 at the
diagnostic module connector.
If the resistance is infinity, check the cable reel
cassette for short circuits. Replace the column
switchgear assembly if necessary. Refit the plastic
wedges. Reconnect the diagnostic module. Clear
the code 34. Rearm the airbags (6.4.21.4).
If the resistance is less than infinity, replace the
main airbag harness. Refit the plastic wedges.
Reconnect the diagnostic module. Clear the code

34.
Rearm the airbags (6.4.21.4).
Since the circuit resistance is in specification, the
fault must lie in the diagnostic module or in the
airbag module.
Substitute a known good diagnostic module. If
code 34 recurs with the airbag simulator fitted,
there is still a fault in the wiring or the simulator.
If the fault code 34 does not recur, rearm the airbags
(6.4.21.4) and retest.
If fault code 34 recurs with the airbag modulefitted,
the airbag module is faulty. Replace the drivers
airbag module (4.5.01.3).
September 1996 6-93

Electrics
Airbag System ^^?
Airbag DM Fault Code 35
Passengers airbag circuit low resistance or short
circuit.
Normal Operation
The diagnostic module measures the resistance
across pins 2-2 and 2-3 every time the ignition is
switched on. The resistance should be 0.9 to
1.1Q..

If the total resistance in the passengers airbag
circuit falls below 0.7S2, fault code 35 will be
declared and the airbag lamp will be illuminated.
f^ote:
The
nominal
resistance
of the airbag simulator
is

2.5£2,
therefore expect
a
total circuit
resistance
reading of
2.4 - 2.6Q with the simulator fitted.
Caution: The passengers airbag connector contains
shorting bars which short circuit pins 1 and 3 of
both sides of the connector when disconnected.
DO NOT REMOVE OR DISABLE THE AIRBAG
CONNECTOR SHORTING BAR UNDER ANY
CIRCUMSTANCES.
The airbag harness shorting bar may be temporarily
disabled during the following resistance checks.
Possible Causes
• Poorly mated airbag harness connector. If the
connector is poorly mated, the shorting bars
may not be fully retracted.
• Faulty shorting bar may short circuit 2-2 and 2-
3 together.
• A short across the airbag terminals in the
passengers airbag module.
Fault Analysis

1.
Disarm the airbag system and check the security of
the passengers airbag module connector before
disconnecting.
If the connector is secure, complete the disarming
procedure, fit the airbag simulators (6.4.21.4). Go
to step 2
If the connector is insecure, service as necessary,
clear the code 35, rearm the airbags. Check that
code 35 does not recur.

2.
Disconnectthediagnostic module and removethe
plastic wedge from connector 2 (black). Measure
the resistance between pins 2-2 and 2-3. The
resistance should be 2.4 - 2.6Q.
If the resistance is 2.4 - 2.6Q, go to step 4.
If the resistance is below 2.4 - 2.6fl, go to step 3.
3. Disconnect the airbag simulator at the passengers
airbag module and remove the plastic wedge from
the harness connector. Measure the resistance
between pins 2-2 and 2-3 at the diagnostic module
connector.
If the resistance is infinity, the airbag harness is
good at this time. Swap the airbag simulators at the
drivers and passengers airbag connectors. Repeat
the resistance check. If the resistance is less than
infinity, there is a fault in the passengers airbag
harness connector. Service the connector or replace
the harness as necessary. Refit the plastic wedges.
Reconnect the diagnostic module. Clear the code

35.
Rearm the airbags.
If the resistance is less than infinity, service the
bulkhead harness as necessary. Refit the plastic
wedges. Reconnect the diagnostic module. Clear
the code 35. Rearm the airbags (6.4.21.4).

4.
Since the circuit resistance is in specification, the
fault must lie in the diagnostic module or in the
airbag module.
Substitute a known good diagnostic module. If
code 35 recurs with the airbag simulator fitted,
there is still a fault in the wiring or the simulator.
If the fault code 35 does not recur, rearm the airbags
(6.4.21.4) and retest.
If fault code 35 recurs with the airbag module fitted,
the airbag module is faulty. Replace the passengers
airbag module (7.8.02.6).
6-94 September 1996

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