Background

Getting an accurate RPM reading is essential to a successful emissions inspection. The OBD-II will read RPMs, but vehicles not equipped with OBD-II will need RPMs measured by a tachometer. There are several common causes of inaccurate RPM readings. When using the Tach Screen, ensure that all engine data is entered correctly. For example, a 6-cylinder engine labeled as an 8-cylinder engine will cause problems reading RPMs. Additionally, selecting the wrong cycle designation will cause an inaccurate reading. Be sure to use the right kind of RPM measuring device for each situation and specify on the Tach Screen which device is used.