OBDII is a set of standards and practices used to fine tune emission programs across vehicle makes and models. We covered Mode 1 which is the ability to request current data display. Mode 1 data is actual data, not enhanced or altered. However, because OBDII is an emission standard and not actually a diagnostic program your available data items are limited.
OBDII Mode 2 is the request of Freeze Frame data. When an OBDII trouble code is set a frame of data is captured at that time. Mode 2 allows the Freeze Frame to be called up for viewing. It can give an idea of the conditions that were present at the time of the fault. There are limited data items, and the frame is not a millisecond of data capture but over the period of a few seconds. Still, the information can often be helpful to diagnostics even though it isn't designed specifically for that. An example would be Freeze Frame for a lean fuel condition. If the Freeze Frame shows the code conditions to be heavy acceleration/ high fuel demand then you can suspect a fuel delivery problem. If the conditions were at idle or low fuel demand then you can suspect a vacuum leak. If you couple that vacuum leak with presence at cold engine temperature then you may even narrow that leak down to an intake manifold sealing problem.
No comments:
Post a Comment