Control Module: Description and Operation

4 A/T Control Unit:

The 4 A/T Control Unit, located under the dash left of the steering column, is the control unit for various electrically operated functions of the N4A-HL automatic transmission. One of these functions is torque converter lockup or lockup inhibit, activated according to operating conditions. Control of ATF flow to the torque converter and lockup are achieved by 4 A/T control unit energizing and de-energizing the lockup solenoid on the transmission. The ATF passage is closed when current is applied and open when it is cut off.

To coordinate engine operating conditions with transmission functioning, the ECU sends a signal to the 4 A/T control unit (an output from the ECU). The signal informs the 4 A/T control unit of engine throttle position, an input used to calculate lockup control. Lockup is permitted during most driving conditions but specifically inhibited when the 4 A/T control unit receives a wide open throttle signal from the ECU.