1997 ASTON MARTIN DB7 airbag off

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Electrics
Airbag System
Airbag DM Fault Code 12
Low battery voltage
Normal Operation
The airbag diagnostic module (DM) monitors the
voltage at pin 1-7 which should be equal to the
battery voltage. If a voltage lower than 9 volts is
detected at pin 1-7, the airbag warning lamp will be
illuminated and fault code 12 will be flashed.
Possible Causes
Drop in battery voltage to DM pin 1-7 caused by:
• Open circuit to pin
1
-7 from the battery
• Short circuit to ground on the battery feed
circuit
• Safing sensor feed shorted to ground
• Safing sensor internal short to ground
• Faulty charge system draining the battery
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.
Complete a battery voltage test as follows:
a) Measure the battery voltage at the battery under
KOEO and KOER conditions.
If the battery voltage is below 10.5 volts during
KOEO or below 12.5 volts during the KOER tests,
service the battery
and
charging system
as
necessary.
Retest for airbag system fau
It
code 12 and go to step
2 if the fault recurs.

2.
Complete a 12 volts supply check at the diagnostic
module:
a) Disarm the airbag system and fit airbag simulators
(6.4.21.4)
b) Disconnect the airbag diagnostic module.
c) Switch on the ignition.
d) Measurethevoltagebetween DM hamessconnector
pin 1-7 (+) and harness connector pin 1-3 (-).
e) If battery voltage is not present, go to step 3.
If battery voltage is present at pin 1-7, renew the
diagnostic module. Rearm and verify the airbag

system.

3. Check the supply fuse as follows:
a) Check fuse F16 in the passenger side fusebox RHD
(or F18 in passenger fusebox LHD).
If the fuse has not blown, check for an open circuit
between battery positive and diagnostic module
connector pin
1
-7.
If the fuse has blown. Renew the fuse and/or repair
the wiring and go to step 4.

4.
Check for a short circuit as follows:
a) Switch off the ignition. With the airbag diagnostic
module disconnected, measure the continuity to
earth from diagnostic module connector pin
1
-7 to

ground.

If no short circuit is detected, go to step 5.
Ifashortto ground isdetected, service the wiring as
necessary. Reconnect the diagnostic module and
retest to ensure that code 12 is cleared.
5. Check for a short circuit to ground on the safing
sensor wiring as follows:
a) Check for a short circuit to ground at diagnostic
module pin 1-9.
b) If a short is detected, disconnect the safing sensor
and repeat the check at diagnostic module pin
1
-9.
If a short is still detected, service the wiring from
diagnostic module pin
1
-9 to safing sensor pin 7.
c) If no short circuit is detected, change the airbag
diagnostic module. Reconnect the diagnostic
module and retest to ensure that code 12 does not
recur.
6. Rearm the airbags (6.4.21.4)
September 1996 6-85

mxm^^^?
Electrics
Airbag System
Airbag DM Fault Code 14
Primary crash sensor circuit short to ground
Airbag DM Fault Code 21
Safing sensor insecure mounting.
Normal Operation
The diagnostic module measuresthevoltage at pins

1
-2 and
1
-6. The normal voltage at these pins is 10
volts (±1 volt) with the ignition on, and battery
voltage with the ignition off.
If the voltage at the airbag diagnostic module
connector pins
1
-2 or
1
-6 drops below 5 volts, fault
code 14 will be generated and the airbag warning
lamp will be switched on. When generating a code
14 the diagnostic module also generates a signal to
blow its own internal thermal fuse. This action
disables the airbag deployment circuit. The airbag
diagnostic module fuse is non-repairable and the
module must be replaced after removing the short
circuit. If the voltage at pins 1-2 and 1-6 returns to

normal,
fault code 51 (blown thermal fuse) will be

logged.

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.
Disconnect the airbag diagnostic module and
remove the plastic wedge from plug
1
(slate).
Note:
The
plastic wedge contains a shorting bar which
would
short
together pins
1-3
(gnd),
1-11
and 1-2 when
the plug is disconnected.
3 Measure the continuity to ground at the following
pins on the diagnostic module harness connector:
1-2 RH crash sensor monitor
1-11 LH crash sensor feed

1
-6 LH crash sensor monitor
1-12 RH crash sensor feed
If no short circuit is detected, go to step 4.
If a short circuit
is
detected, disconnect the relevant
crash sensorandrepeatthecontinuity measurement
to isolate the circuit fault. Service the wiring or
replace the crash sensor as necessary. Refit the
plastic wedge to the diagnostic module connector.
Fit a new airbag diagnostic module and rearm the
airbags (6.4.21.4).
Normal Operation
The diagnostic module measures the resistance
between pins
1
-10 (safing sensor case ground) and
1-3 (monitor reference ground) at the diagnostic
module connector. If the resistance is greater than
2Q
a
fault code
21
will be generated and the airbag
warning lamp will be switched on.
Note:
a
good ground connection is vital.
The
wire from
pin
1-1
is riveted to the safing
sensor case
and the
case

must
be securely
grounded to the vehicle
body.

Fault Analysis
WARNING: Read and adhere to all warnings and
safety procedures at the start of this section when
working on the airbag system.
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Disconnect the diagnostic connector and check for
continuity from pin 1-3 to chassis ground.
If continuity is good, go to step 3.
If the resistance reading is 2Q or more, service the
diagnostic module ground circuit to pin 1-3 as
necessary. Confirm a good ground path between
pins 1-10 and 1-3.Clearthecode21 and rearm the
airbags (6.4.21.4).
Check for continuity between pins
1
-10 and chassis
ground at the safing sensor.
If the resistance is above 2Q, check for continuity
from the safing sensor connector pin 5 to chassis

ground.
Also check the safing sensor mounting for

corrosion,
dirt or loose fixings. Service the wiring
and/or clean and secure the sensor mounting as
necessary, if a satisfactory ground is not achieved,
replace the safing sensor.
Make
a
final continuity test from diagnostic module
connector pin
1
-3 to
1
-10 to ensure a satisfactory
ground
path.
Reconnect the diagnostic module.
Clear the code
21.
Rearm the airbags (6.4.21.4).
September 1996 6-87

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

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

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