Purpose of the test
The operation of a countershaft transmission involves the transmission ECM receiving inputs, evaluating the inputs and, then, energizing one speed clutch solenoid and one directional clutch solenoid. When a speed clutch solenoid is energized, the appropriate speed selector spool routes pressurized oil to a speed clutch causing it to engage. Similarly, when a directional clutch solenoid is energized, the appropriate speed selector spool routes pressurized oil to a directional clutch causing it to engage.