Checking the Signal From the Central Locking System

Fault symptom
Fuse 20 for the central locking system blows
The alarm cannot be activated/deactivated

Diagnostic procedure
1 Check that fuse 20 is intact and live with current.
2 Connect the Intelligent Saab Tester (ISAT). Select the "OBTAIN READ-OUTS" menu and then select "UNLOCK SIGNAL" of "LOCK SIGNAL".
Turn the key in the driver's door to the right or left and read the ISAT display.
During activation-> "ON"
End and neutral position-> "OFF"
3 If these readings are not obtained, connect the BOB and check the voltage by measuring across:
- pin 20 of the control module and a good grounding point while locking.
- pin 11 of the control module and a good grounding point while unlocking.
A reading of about 12 V should be obtained for about 750 ms.
If it is, proceed to point 6.




4 If it is not, check the voltage at control module for the central locking system by measuring across:
- pin 12 of the control module and a good grounding point while locking.
- pin 8 of the control module and a good grounding point while unlocking.
A reading of about 12 V should be obtained for about 750 ms.
If it is not, continue fault diagnosis as described in the "Central locking system" wiring diagrams.
5 If voltage is present, check the wiring for a short circuit by measuring the resistance, which should be < 1 ohm.

Measure across:
- pin B of the central locking connector and pin 11 of the anti-theft alarm connector.
- pin 12 of the central locking connector and pin 1 of the microswitch in the driver's door.
- pin 2 of the microswitch in the driver's door and pin 20 of the anti-theft alarm connector.
If the resistance is correct in the two latter points, the microswitch is probably at fault. Change the microswitch.