Check Engine Request

If an emission related fault arises in the automatic transmission, the transmission control module sends a PWM signal at a frequency of 2 Hz from pin 5 to engine control module pin 65 (Motronic 4.1).

The engine control module then causes the CHECK ENGINE lamp (MIL) to light up.

When the ignition switch is turned to the ON position, the control module sends a ground pulse for 1 second as an operational check.