fuse ASTON MARTIN DB7 1997 User Guide

Electrics

Relay Location Index - 97 MY
D^^
Facia Component Panel
- LHD
Passenger
Function
Heated Front Screen Timer Relay
Multi-Function Module
Low Coolant Transmitter Module
Main Relay (Red Stripe)
Auxiliary Load
Auxiliary Load
Fusebox
Heated Front Screen Fuse
Otter Switch (door drop glass)
Side
-
Right
to
Left
Base Colour
Yellow
Black
Black
Red
White
Black
Black
White
Fascia Component Panel
- LHD
Drivers Side
-
Right
to
Left
Function
Gearbox Failure Warning
Ignition Load
Courtesy Lights
Indicator/Flasher Unit
Hazard Warning
Heated Rear Window
Rear
Fog
Light
Dimmer Module
Fusebox
Base Colour
Black
White
Red
Yellow
Green
Blue
Brown
Black
Relay/Module Cover.
Grey
Black
Black
Silver
Blue
Blue
Orange Fuse
Black
Relay/Module Cover.
Pink
Blue
Blue
Black
Black
Blue
Blue
Red
Location
1
2
3
4
5
6
7
8
9
Location
1
2
3
4
5
6
7
8
9

Seat Heater Relays - Beneath the Driver and Passenger Seats
Boot (Trunk) Relays Volante (Front To Rear)

Function
LH Quarter
Up

LH Quarter Down
Hood Down
Hood
Up

RH Quarter Down
Reverse Lights
Fuel Pump
1

Fuel Pump
2

Tilt Sensor
RH Quarter
Up

Stop Lights
Hood Lift Fuse
Fusebox
Hood (Roof) Control Module
Thermal Cut-Outs Quarter Glasses
Base Colour
White
Yellow
Blue
Green
Red
Yellow
Blue
Green
White
Black
Brown
Black
Relay/Module Cover.
Pink
Pink
Pink
Pink
Pink
Blue
Silver (Bosch)
Silver (Bosch)
Pink
Pink
Blue
Green
30A

Black
Location
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

Boot (Trunk) Relays Coupe (Front To Rear)
Function
Stop Lights
Reverse Lights
Fuel Pump 1
Fuel Pump 2
Tilt Sensor
Fusebox
Base Colour
Brown
Yellow
Blue
Green
White
6-66

Relay/Module
Blue
Blue
Silver (Bosch)
Silver (Bosch)
Pink
Cover. Location
1
2
3
4
5
6
September
1996

NO 140 141

COLOUR
PIN
NV
1
B
2

AREA 3.C4 3,A2

NO 14? 143

COLOUR
PIN
NP
1
m
2

AREA 3.05 3.D4
< lOlO
5! —fsi Q: 3 O _J O
(O
omcD
.

f

i^<S(c

q
ifll?

< rrt

o
Si
il

*s
H
Jz

NO COLOUR 928
B
929
KB
177
BO

172
BG

PIN B9 86 87 87A 30
AREA
3.85-28
3.B3-25
3.D4
3.01
NO COLOUR
PIN
151
B 85
152
U 86
153
OY 87
e7A 150
NS 30

AREA
3.B4-28
3.B3-26
3.A5
3.A6
NO COLOUf 154
W8
155
KB
156
W
157
GU
153
BY

PIN 85 86 S7A e7A 30
AREA 3.D3
3.B5-25
3.B4
3.B5-27
3.A4
FAN
RUN
ON
RELAY
I
87
II
BLUE BASE

87A
AIR
CON
RELAY AIR
CON
W.O.T.
DW|

I
87
II
GREEN
BASE

am
I
87 II
YELLOW BASE

Is-^sl

SCREEN WASH PUMP

I

•Wl|

3n-^ai
NO COLOUR
PIN
AREA 158
B U
B4-28 156
W W 3.A4

FAN MOTOR
2

NO COLOUR
PIN
162
GU
1
2 3
AREA
3.B4-27

c

NO COLOUR AREA
166
8 3.D4
167
B
3.B2-28 EARTH POINT
OINT|—c

NO COLOUR 168
N
169
N

AREA 3.04 3.03 BATTERY
PCS
'osTj-c:
TRINERY SWITCH
NO 159 160
161
COLOUR ON KU
OP
PIN 1 2 3 4
AREA 3.D6 3.06
06
NO COLOUR
PIN
163
GN
I
164
U 2
148
B 3
165
ua 4

AREA 3.B6 3.B3-26 3.A3 3.D3
FAN CHANGE OVER RELAY Is
>
\,1

NO COLOUf 140
NY
166
B
143
WY

175
NP
176
KB
171
UY
170
UN
177
BG

PIN 1 2 3 4 5 6 7 8 9
AREA 3.AI 3.C2 3.BI
3.D4
3.B5-25
3.02 3.D2 3.A3 "a

D
D
•
D
D
D
hi
D
Q

Dinr
D
D
D
D
D
•

NO COLOUF 180 GW
150
NS

138
YR
178
BK
149
WR

163
GN

145
LGB

147
BS

PIN 1 ? 3 4 5 6 7 B 9 10 II 12 13 14 15 16 17 18 19 20
AREA 3.05
3.A4
3.D5 3.D5 3.A3
3.DI
3.A2
3.A2
NO COLOUR
PIN
159
ON 1
160
KU 2
161
OP 3

AREA 3.DI 3.DI 3.DI
J RH
Sll
I REPEA SIDE 1 REPEATER NO 179 180
COLOUR B GW
AREA 3.B4-3.B6 28
NO COLOUR
PIN
170
UN I
181
KB 2
171
UY 3
172
BG
4
5
6^
AREA 3.D4
3.B3-25
3.04 3.A3
NO 173 154 165 174
AIRCON CONTROL
COLOUR U WB UB GU
PIN 1 ? 3 4
AREA 3.B3-3.A5 3.01 3.B4-
26
27
r
^2
FAN FUSE NO COLOUR
PIN
169
N 1
142
NP 2

AREA 3.C2 3.BI
NO COLOUR
PIN
168
N 1
175
NP 2

AREA 3.C2 3.D4
Wiring Diagram
Model
-
Aston Martin
DB7

Harness Title
-
Right Forward
Drawing Part No.
-
B37-84628
Revision
- 0
Sheet
3 of 26 - 97 MY

STOP LAMP
NO COLOUR 807
CB
1097
G
1098
GP

1099
G

RELAY
PIN AREA 85 I4.CI 86 I7.D2 87 I6.B5-I74
87A
30
17X2

REVERSE LAMP RELAY FUEL PUMP RELAY 1

NO COLOUR 803
SLG
1100
W
IIOI
GN

1102
NP
PIN 85 88
8/
R7A 30
AREA M.CI 17.02 I6.B3-I7I
I6B5-I75
NO COLOUfl 335 OR 1103 KB 1087 UG 337 RN 1104 NP
PIN BS R6 87 R7A 30
AREA I4.CI I7.B3-I79 I6.A5 14.01 17.02
FUEL PUMP RELAY 2
NO COLOUR 336 0 1105 KB 1089 UR 809 YN 1106 NP
PIN AREA 85 I4.CI 86 I7.B3-I79 87 le.AG 87A I4.CI 30 I7.C2
TILT SENSOR RELAY
NO COLOUfl 1109 B 1110 WK
nil BO 1112 B
PIN AREA 85 17.84-183 S6 I7.B4-I82 87 87A I4.B4-I58 30 I7.B4-I83

I^OBROWN
BASE
87A ^JSSPBL

[jylYELLOW
BASE

ma

3«-i

J¥tU

SHEET
16
AREA
B6

10 in

'-fts'^B^-'

lijZ-il
[NATURAL
BASE

L 3JA
NO COLOUR AREA 1107
N
17.83-180 llOe
N
17.83-181
NO COLOUR 1125
N
1126
G
1127
G
1128
N
1130
N
1072
R
1075
R
1133
G
1135
N
1137
G
1138
N
1140
N
PIN 1 2 3 4 5 6
/
8 9 10 II
12 13
AREA 17.83-180 16.86-177 16.86-177 I7.B3-I8I I7.B3-I80 14.84-155 14.84-155 16.86-177 17.83-180 I6.B6-I77 I7.B3-I8I I7.B3-I8I
c

SHEET
25
AREA
B/C6

CZE
BOOT FUSEBOX HARNESS
•^-
rp
NO COLOUR
iioe NP 1099 G 1097 G 1129 NP 1115 NS 1131 RS 1132 RG 1134 m 1136 NS 1100 W 1139 NP 1104 NP
PIN 1 2 3 4 5 6 7 8 9 10 II

\l
AREA I7.A3 I7.AI I7.AI 16.83-168 I7.C4 I6.B5-I76 I6.C3-I70 17.84-182 I7.B5-I84 I7.A2 16.85-175 I7.A2

I

D
a
D
D
D
D,
D
c^
D
D
D
0
D
D

NO COLOUR
PIN
1113
VS A
1114
NS B

AREA 17.86 I7.C6

i'^AAA'

ITYRE
COMPRESSORI
NO COLOUR AREA 1115
NS
I7.DI 1116
8 I7.B4-IB3
5^

\_/
SECURITY NO COLOUR 1055
TIN
1026
KB
1117
BR
1118
BR
1028
HI
772
OR
1027
U

1119
WY
3
YS
1113
YS
1120
GR
1121
8
1122
8RD

1021
UO
773
OU

374
0

1
LG
1082
PG
1123
GW
1114
NS
1124
NS

SYSTEM
PIN 1 ? 3 4 5 6
7 8 9 10
II II 12 13
14 15
16
17 18 19 20 ?l
22 23 24 25 2b

AREA I6.C2 I4.B6 16.84-172 16.86-178 14 .C6 I4.CI 14.06
17.84-182 M.BI I7.B5 I5.B1-163 17.84-183 I6.82-I67A
I4.C4 I4.CI
I5.BI
I4.CI ie.C4 16.81-167 17.85 17.85-184
'^7
Wiring Diagram

Model
- Aston Martin DB7

Harness
Title - Rearward - 4

Part
No. - B37-84642

Revision
- 0
Sheet
17 of 26-97 MY

\L^C=£

NO
COLOUR
1106 HP 1099 G 1097 G 1129 NP 1115 NS 1131 RS 113? RG 1134 WK 1136 NS 1100 W 1139 H? 1104 NP
PIN 1 2 3 4 5 6 t S 9 10 II 12 13

AREA
2T.a
2?.CI 27.CI
27.01
27.CI 27.CI 27.C2 27.C2 27.C2 27.C2 27.C2 27.02
SHEET
17
AREA
Dl
NO
COLOUR
1125 N 1126 G 1127 G 1128 N 1130 M 1072 RS 1075 RG 1133 G 1135 N 1137 0 1136 N 1140 N
PIN 1 2 3 4 S 6 7 S 9 10 II 12 13

AREA 27.CI 27.CI 27.CI 27.CI
n.a
27.CI 27.C2 27.C2 27.02
27 C2
27.C2 27.C2
Wiring Diagram
Model
-
Aston Martin
DB7

Harness Title
-
Boot Fusebox
Part
No. -
837-84650
Revision
- 0
Sheet
25 of
26-97
MY
in

^n^P^F^^j^Fj^T^rj^

NO
COLOUF
1125 N
iioe
NP 1126 G 1099
G
1127 G 1097 G 1128 N 1129 NP 1130 N 1115 NS 1072 RS 1131 RS
PIN 1 2 3 4 5 6 / 8 9 10 II 12

AREA I3.C6
13.86
I3.C6
13.86 13.C6 13.86
I3.C6 I3.8G I3.C6 I3.B6 I3.C6 I3.B6

NO
COLOUF
1075 RG 1132 RG 1133 G 1134 WK 1135 N 1136 NS 1137 G 1100 W 1138 N 1139 NP 1140 N 1104 NP
PIN 13 14 15 16 17 18 19 ?0 21 ?? 23 24

AREA I3.C6
13.86
I3.C6
13.86
I5.C6
13.86
I3.ce
13.86
I3.C6
13.86
I3.C6
13.86

^=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

"^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
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 ^?
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