4 ms·
Not really, When powered down(battery diconnected) the computer then has to re learn parameters/pass internal validity checks. On a well preforming system this
by somat 4y ago
Not really, When powered down(battery diconnected) the computer then has to re learn parameters/pass internal validity checks. On a well preforming system this will be done in as little 1 or 2 rides but on a marginal system this can take many rides. the computer may not enter closed loop mode until these checks pass.
closed loop mode is where the computer set it's output values(fuel air ratio, timing etc) based on it's input sensors. open loop mode is where it sets it's outputs on known safe working values, but it may not run particularly well. i think this is related to the so called "limp mode"
Note My knowledge on this subject is very out of date. I had to figure it out for my old 2001 car. Newer vehicles may actually have flash storage and the computer parameters survive power out.
- aksss 4y agoYes, my Audi did not like being disconnected from power. If I remember correctly, it didn't go into limp mode but it was in some partial alarm state when it reconnected such that one had to mimic the Contra cheat code with their fob to get it to shut up. I jest, but yeah. Battery dead was not a condition with a transparent recovery.
- tempestn 4y agoNot to mention more minor annoyances like losing radio stations and other settings.
- gsich 4y agoIt's insane that this keeps happening. Computers can remember BIOS settings for probably 40+ years now.
- waych 4y agoBut this is usually done on computers with a battery too?
- gsich 4y agoI know.
- tempestn 4y agoYeah, there are lots of ways cars could store such settings that wouldn't be cleared when main battery power is disconnected (which is something that regularly needs to be done when the car is serviced). Flash storage would work too.
- somat 4y agoThey use a battery backup. The main symptom of having a dead cmos battery is that your computer starts loosing it's cmos settings, it's a feature not a bug. I have a system where it keeps the cmos config on flash. the only system I managed to brick(almost). I put a bad config in(never disable usb on a laptop where everything is usb) and there was no easy way to reset it. I had to buy a sioc clip and a chip programmer to reflash the thing the hard way. The point is all cars have a wonderful battery backup system, and resetting the computer when power is lost is also a nice feature.