The "engine speed sensor" is a magnetic pickup that is triggered by segments on the flywheel. It is an input device to the MAS. The TD signal is an output signal from the MAS. The TD signal can be checked at the port/terminal with a voltmeter. If the voltmeter incorporates a tach setting, so much the better; in any case just about any voltage of about +3 or more will be sufficient to drive the in car tach.