Reconnecting battery - things to do?

I just spent the week with the car apart, fixing annoying things and replacing stuff (like the fuel level sender, vacuum reservoir and idle and tensioner rollers). I vaguely remember that there is some special tomfoolery to getting things back to normal after having the battery disconnected. Any guidance would be appreciated.

Nothing really special. If you still have the factory stereo, you'll need the code. If you have seat memory, you'll need to reprogram it. You'll also need to reset the one-touch up and down function on the windows. Odometer trip meter, clock, and OBC (if you have it) will all be reset too. I'm not sure what the official window reset process is, but what works for me is to roll them all the way down (one at a time) and keep holding the button for an extra 5 seconds. Then roll it up and hold for 5 seconds. Otherwise I can't think of anything else I've ever had to do.

Perform a calibration of the e-Gas system. The steps should be in the owners manual. From my 2002 Boxster the steps are with the key off and the foot off the gas pedal turn the key to the 1st position. Leave in this position for at least 60 seconds. Turn the key off for at least 10 seconds. The next time the engine is started the calibration is complete. This calibration should be done more often then every time the battery is disconnected. I try to remember to do it every 5K miles but I forget more often than I remember.

Thanks gnat, I don't have OBD and I have an updated stereo so no problems there - sorry, it was more of a question of getting the car to run right. So Macster, that's more what I was looking for - thanks. Interesting - so we should be doing a recalibration as often as we change oil?

To calibrate, I've always put the key in the 2nd position - ignition on & all the lights on the dash lit - but don't start. Hold that for 60 seconds as Macster says, then off for 10 seconds.

I have had my battery off several times and never had to re calibrate anything. Simply punch in the radio code when asked for and that's it. Mine is the 99 cab. All news to me.

There really is nothing special, just like any other car. You are not re-applying power to the space shuttle! I always picture Gene Wilder in Young Frankenstein...It's Alive, It's Alive!! Hook it up + first then -, set the clock on the dash and take a drive. It takes two cycles of about 20 minutes of driving each for the DME to go through the entire engine re-calibration learning curve. You will hardly notice it.

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Macster is the 996 librarian and I trust any information he provides, but his comment is the first I've heard of that procedure. As Joe said, I get in it, reset the clock and windows, and drive off. Never noticed it not running right or even differently.

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With the battery disconnected the DME and its fuel trims and other learned adaptions are lost/reset to their defaults. The DME's job is to adapt to what the engine needs ASAP so that's not a problem. The e-Gas system is a bit different. It doesn't adapt. It relies upon voltage differences to control and know it has control of the butterfly valve. The calibration of this I guess lets it experience a steady voltage level for a time to establish some kind of baseline. IIRC the e-Gas calibration is covered in my 2002 Boxster's owner manual. (I seem to recall it being in my 2003 Turbo's manual too, but I'm too lazy, err make that too pressed for time, to walk to the car and check.) If there is nothing in your car's owner manual regarding this the calibration then it may not be necessary. Update: The throttle adaptation is covered in the 996 Turbo factory manual. Here: Problem � After disconnection of the power supply, the idle speed might change or fluctuate briefly until the idle speed positioner (M 5.2) or the throttle adjusting unit (ME 7.2) is readapted. � The mixture adaptation is also lost. Remedy After the battery is connected. With the DME ME 7.2, it is necessary to carry out a learning and adaptation routine as described below: 1. Switch the ignition on for 1 minute without starting the engine. Do not actuate accelerator pedal. 2. Switch off ignition for at least 10 seconds. This completes the adaptation of the throttle adjusting unit.

Well, there we are. The OP did not give the Model/Year so we cannot tell if his car is Throttle cable or E-gas. My 99 C2 is throttle cable. Some 99 C4's are E-gas. Later years are all E-gas. If the Throttle Body has a throttle cable going to it, it is a drive-by-wire and does not require calibration. If it doesn't, then it is E-Gas, electronic throttle control and that does require the calibration as stated-ignition on/no start for 60 seconds/ignition off. Then start it up. Everybody is correct in one way or another, and it all depends on the OP's car.

My car is an '02 so has the egas, but there is nothing in the owner's manual about the calibration process even though they spend 3 pages on the battery. All that's mentioned is the radio code ... and a strange note that says "If the fuel is less than approx. 1/3 of the overall tank capacity while the battery is discharged or disconnected , (their emphasis) incorrect information will be displayed when the battery is charged or reconnected. The fuel level gauge may indicate more fuel than is actually in the tank (... blah, blah blah, so) ... fill the car up with fuel." (meaning, before you disconnect the battery.) The last thing I'm thinking of when I'm disconnecting the battery for repairs, is topping up the tank! That said, I will do the calibration as per Macster's recommendation.

Another thing I learned today is that if you change the fuel level sender you have to recalibrate that system by EMPTYING the gas tank, and then refilling it with exactly 12 litres of fuel. Now, my car takes 64 litres of fuel ....

My throttle body was acting up car was running rough and was throwing p1120 and p1122. I did the e gas calibrate and it solved my problems. So I would agree that it needs to be calibrated every so often. You will hear the throttle body move to confirm procedure was done correctly. Curious on start up do you turn key to position two and wait for gauges to register before turning over, or do yall just put key in and turn it over as soon as you put key in.

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I actually have a useful answer. I think that is only for the carrera 4's. Because of the front wheel drive system the tank is a funny shape. When it gets below 1/3 it is no longer measuring the amount of fuel in the tank but using information from the trip computer to tell you when it is close to empty. If you disconnect the battery all that info is lost so you have to refill the tank and drive a bit and the computer can figure it out next time the tank gets low.

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That makes sense - and the o/m covers the C4 as well ...

Is there anything that needs to be done for the tiptronic in a 2001 model after diconnecting the battery? my shifts seem a litle odd at times. I looked up this thread to see the adaptation procedure to see if that helps things out but I was wondering if the TCU needs some sort of calibration. Cheers.

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From my limited knowledge of the tiptronics i'd say the shift changes are due to the car losing its adaptation to your driving. I'd assume after xx kms (miles as many of you say) it will learn and adapt once again. Someone with one will chime in with a better answer though i'm sure.

when I disconnected my battery...almost 8 years ago...yes 8, I use a tickle charger...funny things were happening all around. I was upgrading the stereo system. my stereo guru guy came back and disconnected the battery again, took the positive wire and attached it to the negative wire away from the battery...for about a minute. Then he reattached the battery like normal. All the gremlins went away... i'm just saying what happened to me...20034CS...had to change amp to change stereo. so, there's another 2 cents... have no clue why it solved my various electrical bugs... m