Test Smog


TSC - Transmission Controlled Vacuum Spark Advanced System

From one source.


If there is a TCS system malfunction, first connect a vacuum gauge in the hose between the solenoid valve and the distributor vacuum unit. Drive the vehicle or raise it on a frame lift and observe the vacuum gauge. If full vacuum is available in all gears, check for the following:

1.  Blown fuse.

2.   Disconnected wire at solenoid-operated vacuum valve.

3.   Disconnected wire at transmission switch.

4.   Temperature override switch energized due to low engine temperature.

5.   Solenoid failure.


If no vacuum is available in any gear, check the following:

6.   Solenoid valve vacuum lines switched.

7.   Clogged solenoid vacuum valve.

8.   Distributor or manifold vacuum lines leaking or disconnected.

9.   Transmission switch or wire grounded.


Tests for individual components are as follows


Idle Stop Solenoid

This unit may be checked simply by observing it while an assistant switches the ignition ON and OFF. It should extend further with the current switched on. The unit is not repairable.


Solenoid Vacuum Valve

Check that proper manifold vacuum is available. Connect the vacuum gauge in the line between the solenoid valve and the distributor. Apply 12 volts to the solenoid. If vacuum is still not available, the valve is defective, either mechanically or electrically. The unit is not repairable. If the valve is satisfactory, check the relay next.



1.  With the engine at normal operating temperature and the ignition ON, ground the solenoid vacuum valve terminal with the black lead. The solenoid should energize (no vacuum) if the relay is satisfactory.

2.  With the solenoid energized as in Step 1, connect a jumper from the relay terminal with the green/white stripe lead to ground. The solenoid should de-energize (vacuum available) if the relay is satisfactory.

3.  If the relay worked properly in Steps 1 and 2, check the temperature switch. The relay unit is not repairable.


Temperature Switch

The vacuum valve solenoid should be de-energized (vacuum available) with the engine cold. If it is not, ground the green/white stripe wire from the switch. If the solenoid now de-energizes, replace the switch. If the switch was satisfactory, check the transmission switch.


Transmission Switch

With the engine at normal operating temperature and the transmission in one of the no-vacuum gears, the vacuum valve solenoid should be energized (no vacuum). If not, remove and ground the switch electrical lead. If the solenoid energizes, replace the switch.