BMW E21 320i Oxygen Sensor Warning Light Reset
This answer is applicable for many BMWs in addition to the one listed below.
car year: 1983
car model: 320i
I replaced the ox sensor but light on dash has not gone off. what else can I do?
The US E21 models with catalytic converters (79-83 320i) have oxygen sensors as well as a warning light that is intended to remind you that the O2 sensor may need replacement. The light is activated by a switching box that is mounted to the driver side front uni-body frame rail. The speedometer cable runs through the box, just follow the cable from the rear of the transmission to the box. On ’80-’83 models, the lower side of the box has a reset button (next to where the input cable is connected). Press the reset button, with the ignition on, to reset the warning light. On ’79 models, the reset button is on the top of the box and requires a small diameter rod to be inserted through a hole to depress the reset button.