Will Disconnecting Car Battery Reset Everything?
Discussion
I was wondering if I disconnect the car battery for about 5-10 minutes and then reconnect it,
what exactly did I just do? I've read that it will reset the ECU but exactly does that mean?
So for example, if my car/engine is tuned (which it is, to APR stage 2+), if I reset the ECU by disconnecting
the battery, does that mean it will reset to the last settings from my APR Tune or will it reset everything to
stock factory settings and completely mess up or delete the mapping/tuning that was done to my car?
Reason why I ask this is because I read if there is a vacuum leak in the intake manifold and the car has been
having problems due to that, when you repair it/fix the leak, the car will now overcompensate because it was
used to the vacuum leak. So I read that after repairing a vacuum leak, you should also reset the ECU so that
the proper amount of air/fuel ratio will be set.
what exactly did I just do? I've read that it will reset the ECU but exactly does that mean?
So for example, if my car/engine is tuned (which it is, to APR stage 2+), if I reset the ECU by disconnecting
the battery, does that mean it will reset to the last settings from my APR Tune or will it reset everything to
stock factory settings and completely mess up or delete the mapping/tuning that was done to my car?
Reason why I ask this is because I read if there is a vacuum leak in the intake manifold and the car has been
having problems due to that, when you repair it/fix the leak, the car will now overcompensate because it was
used to the vacuum leak. So I read that after repairing a vacuum leak, you should also reset the ECU so that
the proper amount of air/fuel ratio will be set.
You should not lose any tuning that has been done by disconnecting the battery It should not be resetting anything engine management related .
Its always a wait and see two days ago we changed the battery on a 14 plate Mercedes sprinter Expecting to code the radio the radio held its code while we did the battery change
Its always a wait and see two days ago we changed the battery on a 14 plate Mercedes sprinter Expecting to code the radio the radio held its code while we did the battery change
Before you just disconnect and reconnect the battery check to see if there's a process to go through, on some cars it's pretty complicated. From memory on some Citroens you need to wait fifteen minutes before you disconnect it and when you reconnect wait two minutes turn the ignition on for a further minute and then you can start it, one of my customers just brought a battery and fitted it himself and it spiked the ECU.
catman said:
cars don't get "used to" vacuum leaks. If it's been repaired, it should run normally.
Tim
Yes, they do. Any catalysed efi petrol engine will have long and short term fuel trims, driven by the oxygen sensor. If a vacuum leak was causing unmetered air to enter the cylinders the engine would run lean, and the fuel trim would compensate for this providing it had enough adjustment range.Tim
These trim values are stored in volatile memory, so removing the vehicle battery for a short while will reset them.
Unless you are removing the battery to deliberately remove all power, then what I do is take an old motorbike battery I have laying around and connect it to the car. I can then remove the battery without worrying about losing radio codes or anything else.
The car ECU maps aren't held in volatile memory, so will not be affected by removing the battery. if it did, then your cars ECUs would all reset to factory every time the battery was removed.
The car ECU maps aren't held in volatile memory, so will not be affected by removing the battery. if it did, then your cars ECUs would all reset to factory every time the battery was removed.
louiechevy said:
Before you just disconnect and reconnect the battery check to see if there's a process to go through, on some cars it's pretty complicated. From memory on some Citroens you need to wait fifteen minutes before you disconnect it and when you reconnect wait two minutes turn the ignition on for a further minute and then you can start it, one of my customers just brought a battery and fitted it himself and it spiked the ECU.
^ ^ This!!A friend of mine used to be an auto-electrician and he used to get numerous callouts to wrecked ECUs caused by people disconnecting the battery before letting the ECU go to 'sleep' properly.
In your case, surely the long-term fuel trim will reset itself in due course when the leak has been fixed?
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