To reset the service light on a BMW, the correct pins on the diagnostic socket must be connected while the ignition switch is turned on. Finding the correct pins depends on the BMW model. Cars made prior to 1987 have early-type sockets, in which case pins seven and one are connected. Newer models have late-type diagnostic sockets and pins seven and 19 must be connected.
Early-type sockets have a red cap located near the intake manifold. With the socket's flat side aligned to the left and counting from the top down, connect pin three of row three to pin three of row four.
Late-type sockets are covered by a large plastic cap held on by a strap. This is located near the oil dipstick or near the firewall on the driver's side. The pins to connect in this type of socket are the pin closest to the back of the car and the pin directly to the right of the center socket piece.
After locating the correct pins, connect them using a jumper wire and turn the key, so the dashboard lights turn on but the car does not start. After a few seconds and after five LED lights in the dash light up, turn the key off and remove it.