How long will a black box hold data?

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How long will a black box hold data?

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How long will black box hold crash data?
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DPatrickRyan
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Re: How long will a black box hold data?

Post by DPatrickRyan »

"It depends"

If you want DTC data stored in the PCM, the Keep-Alive Memory needs external power and so it could already be gone. At the other end of the scale, locked deployment data "should" be stored pretty much forever and can generally not be cleared, short of some hands-on electronics wizardry. In between is where life gets interesting: some data can be cleared after a certain number of keycycles, some will get overwritten by a more significant subsequent event, and some will get overwritten by ANY subsequent event.

So, yeah - "it depends".
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Dwight
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Re: How long will a black box hold data?

Post by Dwight »

A "Black Box" will hold information for 5 seconds and then is recorded over.
Dwight Magee

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Hebert
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Re: How long will a black box hold data?

Post by Hebert »

Dwight:
This is starting to sound like semantics confusion in the ABS discussion. SOME airbag control modules (a more accurate name than "black box") will RECORD as little as 2.5 seconds of data and others will RECORD as much as a little over 5 seconds. Once RECORDED, there are things that have to happen before the module will overwrite data and "time" isn't one of them.

But here's where we're back to semantics: what's being meant by "hold data"?

Prior to a crash, an airbag control module will "hold" pre-crash data in a ring buffer and, in that regard, that ring buffer can be 2.5sec to about 5 sec "long." (I'm excluding PCM data here which can go almost 7 minutes in some PCMs.) In that case, if we say "hold" means "holding it in the ring buffer before it's recorded," then what you wrote is true, the pre-crash data is only "held" in the module for up to 5 seconds then it's overwritten in a continuous loop.

The question didn't specify pre-crash data or pre-crash and crash pulse data but if we're talking about pre-crash AND crash pulse data, and we say (like you seem to have here) that "hold" means "RECORDED" to the EEPROM, once it's recorded it stays recorded regardless of some time element. Once it's RECORDED, it stays recorded until (in some cases) another event happens and it can be overwritten, or it's locked permanantly (e.g. if it relates to a deployment and is locked). But in both cases, the "hold" - if we say that means RECORDING - is not related to time.
T. Ted Hebert

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