Checking the Brake Light Switch (TCS)

In order for the Cruise Control system to work, at least one of the brake light bulbs must be OK.

This means that pin G (7) of the Cruise Control connector must be grounded (through the brake light bulbs) before the Cruise Control system can be activated.

1 Check that the brake light bulbs are OK.
If they are not, change them and check the brake lights once again.
2 If the brake lights do not work, continue fault diagnosis as described in the "Brake lights" section of Service Manual 3:2 "Electrical system, system diagrams, operation and fault-tracing".
If the brake lights work, check the operation of the Cruise Control system.
3 If the Cruise Control system still does not work, check that about 12 V is present across pin G (7) of the Cruise Control connector and a good ground when the brake pedal is depressed. If the voltage is OK, continue fault diagnosis as described "Before Control Module Replacement".







4 If the voltage is not OK, connect an Intelligent Saab Tester (ISAT) Scan Tool and go to the TCS system. Select "BRAKE LIGHT SWITCH" in the "OBTAIN READOUTS" menu. Check system operation.
If OK, continue with point 5.
If not OK, proceed to point 6.
5 Select "DISENG CRUISE CONT" in the Scan Tool's "OBTAIN READOUTS" menu and measure the voltage across pin G (7) and a good ground.
When "DISENG CRUISE CONT" is ON, the voltage should be about 12 V.
If the voltage is OK, continue fault diagnosis as described "Before Control Module Replacement".
If the voltage is not OK, continue with point 7.







6 Check the wiring for continuity or a short circuit by measuring the resistance across pin 1 of the brake lights switch connector and pin 23 of the TCS control module connector.
If the resistance is > 1 ohm, rectify the fault.
If the resistance is ≤ 1 ohm, continue with point 8.
7 Check the wiring for continuity or a short circuit by measuring the resistance across pin 5 of the TCS control module connector and pin G (7) of the Cruise Control connector.
If the resistance is > 1 ohm, rectify the fault.
If the resistance is ≤ 1 ohm, continue fault diagnosis as described in "Traction Control System".