What is the recommended procedure for resetting or restoring electrical components after a battery disconnect/removal (more than a day)?

How does starting vs driving the car affect this? Or does it matter at all? I have read different things in threads but some were old, so what is the current consensus?

Thanks

 

not to be too snarky, but for me on my 89 S4, it is simply reconnect as that is what i have done to no known ill effects as it has a tendency to drain batteries between my ability to drive it and never seems worse the wear after a removal /charge/reinstall.

 

"Reassembly is a reversal of dismantling."
-Every Haynes Manual

 

Step 1 - Connect the Battery.
Step 2 - Start the car (assumes the battery is charged).
Step 3 - Reset the clock & radio presets
Step 4 - Drive & enjoy.

I know there are some modern cars that require the battery to be connected and then the car left to sit for a period of time.
There are a couple that you are supposed to go through the 're-set' procedure for the transmission (?).

Not on a 928, that I have ever heard.

 

Thanks, and you're right, re-connection seems straightforward enough, God knows I've screwed up the simple tasks as often as the tough ones. I could have asked the question a little clearer regarding the impact on e.g.ECU mapping, MAF, CO2, O2, ISV. The conversation around "unintended consequences" or "jump starts" pop into my mind. So, trying to understand the process a little more, not that I do!

"Adaptation"....that is what I remember stumbling onto a while back. Not sure if this happens only through external software manipulation or, as a built in reset function of the car. Another RL member had posted this Porsche quote addressing adaptive memory strategy:
“Due to the storage of carried-out curve displacement in the memory, the engine will have to be run about 10 minutes at first after an interruption of the permanent pulse to the control unit, e.g. caused by disconnecting the battery or pulling off the 35-pin plug on the injection control unit, which cancels the displacement, in order to permit correct adaptation to the nominal values.” FWIW
Thanks

 

""jump starts"

I dont think there has been enough available information that says jump starts are bad things to do. I believe it's anecdotal. Here is the manual in it's entirety, on jump starting. We're nothing special in the automotive world WRT jump starting.

 

Maybe John Speake will see this and reply, but absent that... I don’t believe that the 928 LH is anything like modern automotive computers that process and store data points as the car is driven to set parameters, make adjustments, for best operation / function of the various systems.

 

87+ certainly does.

 

Right. The adaptation memory will be wiped out with a battery disconnect (I think it has to be left disconnected for 'a period of time').

It will go back to the default settings.

But it will 're-adapt' after driving the car. No extra steps needed.

Is there any need for the battery to sit, connected, with the car not running or driving?
Is there anything that needs to 'fully reboot' before starting and/or driving?
Is there anything that needs a 'reset procedure' after reconnection?

It's my understanding that there are new(er) cars that need those steps to drive properly after a battery disconnect (battery left disconnected long enough for the backup capacitors to completely discharge and have the computers completely dead).
The car can be started & driven right away, but the adaptation will be screwed up and it will take some driving time to get it back to 'normal'.

If I read it correctly, that's what the OP is asking about.

 

Are you sure about that?

 

84/85 MAF 2.2 Euro and 85/ 86 USA computers don’t adapt

the 87 onwards Computers do so a battery disconnect for a few seconds will allow the memory parameters to reset

Note the jump starting info should only be used as a last resort to recharging the battery with it disconnected from the car
now that the charging system component are old it’s easy to damage alternator diodes and the computers and relays with voltage spikes. The Owners manual info about jump starting was written with brand new wire and components in mine not 30 yo systems
This could also include the digital dashes
I have had a few cars from a dealer with similar issues due to the cars with dead batteries being jumped with the 200amp quick boost chargers the reverse light relay gets smoked this takes out the dash odometer and alternator diodes frying and smoked computers