ignition ASTON MARTIN DB7 1997 Owner's Manual

Electrics
Airbag System ^2?

6.4.21.4
Airbag Disarming/Arming
Procedures
WARNINGS AND CAUTIONS:
WARNINGS:
Disarm the airbags by disconnecting the battery
ground (black)
lead,
waiting one minute and then
removing the airbag modules before servicing of
any airbag or steering column component.
After disconnecting the battery ground
lead,
allow
a minimum of one minute delay for the back-up
power supply to discharge before servicing the
airbag system.
The system components are non-serviceable, if
faults are
suspected,
change components for new
items
only.

Failure to observe the above procedures may
result in accidental deployment of the airbags.
Always wear safety
glasses
when working on airbag
equipped vehicles.
Personnel carrying an airbag module must ensure
that the module and trim cover are pointing away
from the
body.
When positioning on a bench or
work surface, ensure that the airbag module and
trim cover face upwards to limit motion on
accidental deployment.
Always wear
gloves
when handling deployed airbag
modules. Deposits of sodium hydroxide may be
presenton the module surface. If sodium hydroxide
contacts any area of the skin, wash the affected
area immediately with mild soap and
water.

Dispose of the deployed airbag using the correct
procedures referred to in this section.
Cautions:
When scrapping vehicles,
ensure
that the
airbags
have
been deployed (see
Scrapping Vehicles
with Live
Airbags).

If a component
has been
renewed and the fault
does
not

clear,
refit the original item and repeat the diagnostic
procedure.
After
servicing,
repeatthe diagnostic
procedures
to ensure
correct
system
operation.

Renew
the airbag module if the surrounding trim
panels

are
damaged.
Do not attempt to repaint trim covers as
paint may
damage
cover material.
Disarming the Airbags
3.
4.
WARNING: Carry out the following disarming
procedure before attempting any work on the
vehicles electrical
systems.

Note: The battery ground (black) lead must be
disconnected within 12 seconds of switching off the
ignition to avoid the alarm siren sounding.
Disconnect the battery ground
lead.
Allow a
minimum of one minute delay for the back-up
power supply to discharge.
Remove the drivers side airbag module and replace
it with an airbag simulatorfrom the simulator kit (Pt

No.
43.27028).
Remove the passengers airbag module and replace
it with an airbag simulator from the simulator kit.
Reconnect the battery ground.
Rearming the Airbags
WARNING: Carry out the following procedure to
rearm and check the airbags after completing all
work on the vehicles electrical
systems.

Note: The vehicle battery
must be
disconnected within
12
seconds
of switching off
the
ignition
to
avoid the alarm
siren sounding.
^. Disconnect the battery ground
lead.
Allow a
minimum of one minute delay for the back-up
power supply to discharge.

2.
Removethedriverssideairbagsimulatorand replace
it with the drivers airbag module. Secure the airbag
module with the two captive torx screws.
3. Remove the passengers side airbag simulator and
replace it with the passenger side airbag module.
Secure the module with four nuts and washers.
Close the passenger side airbag door.

4.
Reconnect the battery ground.
5. Switch on the ignition and check for correct
indications from the SRS/AIRBAG warning light.
TheSRS/AIRBAC lamp should come on after
a
brief
delay and remain on for approximately six seconds
during the airbag system self check. The lamp will
extinguish upon satisfactory completion of the self
check, or will flash a diagnostic code if an airbag
system fault is detected. Continuous illumination of
the warning lamp may indicate a seatbelt
pretensioner fault
Note:
Reset the
clock and window
ECUs
on completion.
6-80 September 1996

^=2?
Electrics
Airbag System
Airbag Diagnostic Module Fault Codes
Fault codes may be extracted in one of two ways:
Through the upper diagnostics connector using the PDU, or as a series of flashes of the SRS/AIRBAG warning lamp.
Each series of flashes represents a two digit number, representing a fault code from the list below which is recorded
in priority order (i.e. If two faults are present, the code nearest the top of the list will flash. Clear the first code, then
the second code will flash). Fault analysis procedures for each code are included on the following pages.
_ No Airbag warning lamp - Inoperative airbag warning lamp or no ignition voltage to the diagnostic module
Continuous airbag warning lamp- Diagnostic module disconnected or inoperative, or a seatbelt pretensioner
fault (see pretensioner diagnostics).
12 Low battery voltage
13 Airbag circuit shorted to ground
14 Front crash sensor circuit shorted to ground
21 Safing sensor incorrectly mounted in the vehicle
22 Safing sensor output circuit shorted to battery voltage
23 Safing sensor input feed/return open circuit
24 Safing sensor output feed/return open circuit
32 Drivers side airbag circuit high resistance or open circuit
33 Passengers side airbag circuit high resistance or open circuit
34 Drivers side airbag circuit low resistance or short circuit to ground
35 Passenger side airbag circuit low resistance or short circuit to ground
41 Front right crash sensor feed/return open circuit
42 Front left crash sensor feed/return open circuit
44 Front right crash sensor incorrectly mounted on the vehicle
45 Front left crash sensor incorrectly mounted on the vehicle
51 Diagnostic module internal fuse intermittent or short circuit to ground
52 Back-up power supply - overvoltage fault
53 Front crash sensor circuits resistance to ground or internal diagnostic module failure
Rapid continuous flashing of the airbag lamp (no fault code)- all front crash sensors disconnected
September 1996 6-81

Electrics
Airbag System ^^?
Airbag Diagnostic Module Connector
The wiring to the airbag diagnostic module passes through two plugs into a single socket. Plug
1
is grey coloured,
plug 2 is black. To aid in fault analysis, the diagnostic module connector pins for plugs
1
and 2, and their functions
are listed below:
Connector 1 - Grey Colour
Pin No. Colour Circuit
Connector 2 - Black
Pin No. Colour Circuit
1-1
1-2
1-3
1-4
1-5
1-6
1-7
1-8
1-9
1-10
1-11
1-12
LGS
ON
B
YW
B
YU
RW
-
RN
RG
KU
KG
12V Ignition Supply
RH Crash Sensor Monitor
Ground
Airbag Warning Lamp Output
Ground
LH Crash Sensor Monitor
12V Battery Power
Not Used
Safing Sensor Input
Safing Sensor Ground Monitor
RH Crash Sensor Feed
LH Crash Sensor Feed
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
-
RP
KP
KN
RP
YG
-
OP
ow
-
YP
-
Not Used
Passenger Airbag Module Feed
Passenger Airbag Module Return
Drivers Airbag Module Return
Drivers Airbag Module Feed
Safing Sensor Output Monitor
Not Used
LH Crash Sensor Ground Monitor
RH Crash Sensor Ground Monitor
Not Used
Safing Sensor Feed
Test Input
Plug 2 Piugl
/LrLrLruuTJu—LrLrLrLrLrLnj
OOO
Connector 2/12-Way/Black
YG RP 3 KP

mn

10 9 OW
Connector 1/12-Way/Grey
6 YU 5 B
12 KG 11 KU 10 RG
4 YW
I
ON LGS
0
6
12 'I J'
6
12 J
6-82 September 1996

"^p
Electrics
Airbag System
No Airbag Warning Lamp

I
noperative lamp, lamp ci rcu it or no ign ition voltage
to the diagnostics module
Normal Operation
The airbag warning lamp is designed to illuminate
for approximately six seconds when the ignition is
switched
on.
This period
is
allocated for satisfactory
performance of the airbag system self test.
Note: The a irbag warning lamp is
driven
by
the instrument

pack and not directly by the airbag diagnostic module.
The airbag diagnostic module requires an ignition
supply to pin
1
to energise the airbag warning lamp
circuit. If the warning lamp circuit is open, or the
diagnostic module does not receive an ignition
voltageatpini, the warning lamp will not illuminate.
Open circuit in the warning lamp supply, in
conjunction with another system fault, will cause
the diagnostic module to emit five tones every 30
minutes while the ignition is switched on. Repair
the faulty circuit before further diagnosis.
Note:
The
diagnostic module will not emit
the
five tone
signal if the warning lamp
is
open circuit and
there
is no

system
fault.

Possible Causes
Defective airbag warning lamp
Faulty wiring in the airbag warning lamp circuit
Loss of ignition voltage at diagnostic module pin 1.
Loss of ground at diagnostic module pin 3
Instrument pack fault
Fault Analysis
WARNING: Read and adhere to all warnings and
safety procedures at the start of this section when
working on the airbag
systent.

1.
Remove the instrument pack and check the airbag
warning lamp.
If the lamp is good, go to step 2.
If the lamp is defective, replace it, switch on the
ignition and check that the lamp is now on for
approximately six seconds after ignition on.

2.
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
9.
Connect the PDU. Switch on the ignition. Measure
the 12V ignition supply voltage from airbag
diagnostic connector pin
1 -1
{+) to chassis ground.
If ignition voltage is present, go to step 6. If ignition
voltage is not present, go to step 4.
Checkfuse F15passengersidefuseboxRHDorF17
passenger side fusebox LHD (Ignition supply to the
diagnostic module pin
1
-1). If the fuse is good, go
to step 5. If the fuse is replaced, go to step 6.
Check for an open circuit on the YW wire from fuse
F15 passenger sidefusebox(F17 LHD)todiagnostic
module pin 1-1. If continuity is good, isolate the
fault in the 12V supply to fuse Fl 5 (Fl 7) and then
go to step 9.
Measure the voltage from diagnostic module pin
1
-
1 to diagnostic module pin 1-3. If 12V is not
present, isolate and service the open circuit in the
diagnostic module ground to pin 1-3. Then go to
step 7.
Switch the ignition off. Set up to measure the
voltage from DM pin
1
-4 to DM pin
1
-5 during the
first six seconds after ignition on.
Switch on the ignition, the warning light signal to
the instrument pack should switch for six seconds
after a brief delay.
If the signal does not switch, the diagnostic module

is
fau Ity. Replace the modu
le,
switch on the ign ition
and check that the airbag warning lamp does light
for six seconds after ignition on.
If the signal does switch for approx. six seconds
after ignition on, the fault is in the instrument pack
or wiring, go to step 8.
Check continuity of the YW wire from diagnostic
module pin
1
-4 to instrument pack 16 way plug pin

2.

If continuity is good, service the instrument pack
and then retesttoensure correct indication from the
airbag warning lamp at ignition on.
If continuity is defective, service the wire and then
retest to ensure correct indication from the airbag
warning lamp at ignition on.
Disconnect the PDU, and rearm the airbags
(6.4.21.4). Switch on the ignition and check for
correct indications from the airbag warning lamp.
September 1996 6-83

Electrics
Airbag System [EE:^^^?
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 will
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 DM
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

^^?
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

Electrics
Airbag System ^2?
Airbag DM Fault Code 13
Airbag circuit short to ground
Normal Operation
The diagnostic modu
le
measures the voltage at pins
2-5 and 2-6. The voltage at these pins is dependant
on charging system voltage as shown in the table

belovi-.

'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
Charge Volts
9.0V
9.5V
lO.OV
10.5V
11.OV
11.5V
12.0V
12.5V
13.0V
13.5V
14.0V
14.5V
15.0V
15.5V
16.0V
If the diagnostic monitor measures a voltage of 2.0
volts or less on pins 2-5 and 2-6, a fau It code 13 will
be generated and flashed to the instrument pack to
be signalled on the airbag warning lamp. Voltages
as low as 2.0 volts indicate a possible short to
ground in these circuits.
When generating a code 13 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 repairing the short circuit, if the
voltage at pins 2-5 and 2-6 returns to normal, fault
code 51 (blown thermal fuse) will be stored in
memory.
6.
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 airbag diagnostic module. Switch
on the ignition.
Measure the continuity to ground at the following
pins on the diagnostic module harness connector:
2-2 Passenger airbag feed
2-3 Passenger airbag return
2-4 Drivers airbag return
2-5 Drivers airbag feed
2-11 Safing sensor feed
If no short circuit is detected, go to step 4.
If
a
short circuit is detected, disconnect the relevant
airbag simulator or the safing sensor and repeat the
continuity measurement to isolate the circuit fault.
Service the wiring or replace the safing sensor as
necessary. Fit a new airbag diagnostic module and
rearm the airbags (6.4.21.4).
Check for intermittent short circuits in the cable
reel cassette. Monitor the continuity to ground at
pins 2-4 and 2-5 whilst rotating the steering from
lock to lock in both directions.
If no short circuit is detected, go to step 5.
If a short circuit is detected, replace the column
switchgear assembly. Fit a new airbag diagnostic
module and rearm the airbags (6.4.21.4).
WARNING: Do not attempt to make any electrical
measurements on the airbag
modules.
Any induced
voltage can
cause
the airbag
to
deploy with the
risk

of personal
injury.

Fit a replacement diagnostic module and
replacement airbag modules.
Caution: Do not refit
the
old
airbag
modules.
They may

be faulty and would
damage the
new diagnostic module.
Rearm the airbag system (6.4.21.4).
6-86 September 1996

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 [D:B3-2?
Airbag DM Fault Code 22
Safing sensor output circuit shorted to battery
voltage.
Normal Operation
The diagnostic module measures the voltage at pin
2-5 (airbag module feed) and 2-5 (safing sensor
output monitor) at thediagnosticmoduleconnector.
The voltage at these pins is dependant on charging
system voltage as shown in the table below. If the
voltage at either pin exceeds 5 volts,
a
fault code 22
will be generated.
in 2-5
2.3V
2.4V
2.5V
2.7V
2.8V
3.0V
3.1V
3.2V
3.4 V
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
3.2 V
3.4 V
3.5V
3.7V
3.8V
4.0V
4.1V
4.3V
Charge 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
Possible Causes
• A short between pins 2-5 or 2-6 and another

wire.
(The wiring to the safing sensor carries
voltages above 5 volts).
• A short between the cable reel cassette circuit
and other 12 volt circu its at the steering column

head.

• A short across the normal ly open contacts of the
safmg sensor.
• Vehiclechargingsystem voltage too
high.
If the
generator output is greater than 17V, fault code
22 may 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.
Disarm the airbag system and fit airbag simulators
(6.4.21.4).
Check the voltage at the battery with the engine
running at approximately 1500 rpm.
If the voltage is 14.8 ±0.5 volts, the charging
voltage is within specification, go to step 3.
If the voltage is significantly above 14.8 volts (the
voltage regulator set point) service the charging

system.
Clear the code 22. Rearm the airbags
(6.4.21.4)
Check in the area of the diagnostic module
connector for harness damage which could cause
a short circu it to 12 volts. (Note: The airbag system
harness runs are sheathed in black plastic protection
and harness damage is unlikely.)
If no harness damage is evident, go to step 4.
If harness damage is identified, service the wiring as
necessary. Clear the code 22. Rearm the airbags
(6.4.21.4).
Switch on the ignition. Monitor the voltage at pins
2-5 and 2-6 whilst rotatingthe steering from lock to
lock in both directions.
If the voltage at both pins remains below 5.0 volts,
go to step 5.
If the voltage rises to above 5.0 volts, service the
cable reel cassette or wiring as necessary. Clear the
code 22. Rearm the airbags (6.4.21.4).
With the ignition on, check the voltage at pins 2-5
and 2-6 whilst manipulating the bulkhead and
safing sensor harnesses.
If the voltage rises above 5.0 volts, service the
wiring fault in the harness area being manipulated
at the time the voltage rise occurred.
If no voltage rise occurs, fit a new safing sensor as
the most likely cause of the code 22. Clear the code
22 and rearm the airbags (6.4.21.4).
6-88 September 1996

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