First what all info is stored? How much data is saved 10sec, 30sec? Is it stored directly in the ECU or some other box? Can this be reset by resetting the ecu?

Just wondering

 

it's stored in the ECU and it can not be erased by just unplug the battery.

 

a snapshot is recorded by your ecu when a code is tripped, so its just a split second of information which has engine rpm and vehicle speed

 

You worried about the accident reporting stuff they've been using lately?

 

There should be a clearing house for this information on all models of cars. After all, insurance adjusters and prosecutors need to know which vehicles this is available from, right?

And as consumers we should know what is in our cars.

And "what all" isn't english.

-PHiZ

 

The ECU only records this type of information when an error occurs. So if you get in an accident, blow your engine, etc. the ECU will record the last 10 seconds of activity prior to the error code.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MyCarGoesVroom &raquo;</TD></TR><TR><TD CLASS="quote">The ECU only records this type of information when an error occurs. So if you get in an accident, blow your engine, etc. the ECU will record the last 10 seconds of activity prior to the error code.</TD></TR></TABLE>

So does the ECU go back in time to record the data after the accident has happened, or does it have ESP and knows when to start recording because there is something about to happen?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Todd00 &raquo;</TD></TR><TR><TD CLASS="quote">

So does the ECU go back in time to record the data after the accident has happened, or does it have ESP and knows when to start recording because there is something about to happen?

</TD></TR></TABLE>

It's called a circular (ring) buffer.

-PHiZ

 

Dang it, you're supposed to come up with some other kind of X-files theory.

 

For the most part OBDII-compliant ECUs stores stuff that is emissions-related. That's because it's primarily been the quest for lower emissions that's been driving the development of ever-more sophisticated car ECUs with all the feedback systems.

By and large, what a modern ECU does is compare actual sensor values with what the values should be. If a sensor stops reporting or reports an unusual value, the ECU records it. Some out-of-range values are simply considere suspicious and the ECU will not store an error code unless that same value occurs a number of times. The ECU will also differentiate between mild and severe errors. Some will then trigger the dreaded "Check Engine" light.

Most stored ECU codes can be cleared with either an OBDII scanner or some other tool. Simply clearing them without knowing what they are is, of course, a very bad idea.

Does our ECU store a lot of data? No. Just error codes. There's one exception and that is fuel trim. The ECU watches your driving while you are in closed loop and will then create a short term fuel trim value, i.e. it adds or removes fuel. Short tem fuel trim affects long term fuel trim, and that is stored.

The computer does NOT (yet) record how you're driving. I think it does record if you go over 9000 rpm, but it won't record how fast you're going or anything. For that you'll want a datalogger.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by conradb212 &raquo;</TD></TR><TR><TD CLASS="quote">The computer does NOT (yet) record how you're driving. I think it does record if you go over 9000 rpm, but it won't record how fast you're going or anything. For that you'll want a datalogger. </TD></TR></TABLE>



Here is the general topic we are discussing:
http://www.techtv.com/news/cul....html

-PHiZ

 

Thanks! I am new to posting on this board (usually hang out at clubrsx and wrote some of the FAQs there) and don't know the history here. Black boxes give me the creeps. As does the proposed OBD-III stuff with transponders and all sorts of other Big Brother goodies.