The B1 switch is the transmissions protective circuit which is found in cars (Mercedes and Porsche 928) with high torque motors. To protect the transmission internal components from high torque loads while up shifting from 1st to 2nd and down shifting from 3rd to 2nd the engine torque will be reduced.

. The B1 band has to be applied for 2nd gear, there is a switch connected to the B1 band pin which signals the controller when the transmission has made a part or full throttle shift into 2nd gear. The ignition controller will retard ignition timing, thereby reducing the torque load to the transmission.

If you disconnect the B1 switch the default will be restarted timing