Hi,

I want to switch off my main battery when the car in parked or the garage, but i don't want to loose the BLM table in my 1227747 ECM.
So, i am thinking that it must be possible to use a small battery just for keeping the memory of the ECM, and maybe also the radio.

Since i'm a rookie on EFI stuff i have som questions that i hope to get answers to:
Is it enough to have +12V on the B1 pin only to keep the memory or is it required to feed also C16?

Is there examples of similar solutions?

I guess that this backup battery must be connected with some components, (diodes, relays...) to isolate it just enough to stay out of trouble and make a good working solution.

Thanks for any comments.
Thomas

 

I have seen people use the cig. lighter to solve this problem. They plug into the cig. lighter with an accessory plug and hook the battery to the other end. This way it is also fuse protected.

 

you'd lose the BLM table by disconnecting the battery?

 

As far as i understand it, all self-calibration gets lost when the ECM is without battery power, it will have to start over again, learning from scratch, and the car might go a little crappy for a while until it has adjusted itself again.

That's why there are such devices as Edwardgp mentions that makes it possible to keep the memory in ECM's and radios while changing battery.

But i think that some cars have a small battery built into the ECM.

 

Yes, i have seen that some kind of stuff like that exists, but i am more after something permanently installed since i plan to use a battery switch that will be switched off every time it's in the garage.

 

I thought that stuff was kept in the chip. I know on the newer cars they sell stuff because the OBD2 systems and their drive cycle monitors. I have disconnected my battery many times and I never lose a tune i have the EBL flash though. anyway. Good luck with that.