Airbag Dm Fault Code 41; Airbag Dm Fault Code 42 - Aston Martin DB7 Workshop Manual

Electrics
Airbag System
Airbag DM Fault Code 41
Right hand crash sensor feed or return open circuit.
Airbag DM Fault Code 42
Left hand crash sensor feed or return open circuit.
Normal Operation
The diagnostic module constantly measures the
voltage at pins 1 -2 and 1-11. The voltage should be
10±1 volt. The two wires are connected together
within the right hand crash sensor. If the voltage at
1-2 falls below that at 1-11, an open circuit has
occurred. Fault code 41 will be declared and the
airbag lamp will be illuminated.
N o r m a l 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 w i l l 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 4 1 . Switch off
and then on again to check that the airbag warning
lamp comes on at 'ignition o n ' 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.
• A n 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.
W i t h 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