Parnelli

but, if i get a new battery for my '97 993 TT will:

1) there be any potential problems with my keyfob?

2) I have any problems with losing stored codes at emmissions time?

3) any other potential concerns?

I guess I was under the impression that if a battery was unplugged that it loses a bunch of valuable codes.

BTW, any suggestions as to what battery to get? It would be at the dealership as I am taking the car in to get an oil change and to have my new Fister mufflers installed

Thx

MarkD

1) there be any potential problems with my keyfob? - No

2) I have any problems with losing stored codes at emmissions time? - Your various readiness flags will not be set. You'd need to do the drive cycle at some point OR they may set over a really long period of time

3) any other potential concerns? - If you have the orignial head unit the radio code will need to be entered

Parnelli

thx Mark. What does this mean exactly?

"You'd need to do the drive cycle at some point" ?

Arena993

Somebody once posted that they kept the Porsche battery maintainer plugged into the cigarette ligter when they changed the battery to keep a charge constant. Never did it, just remember the post.

Mike

911Dave

Plugging the battery maintainer into the cigarette lighter won't do a thing...with the battery out, neither the cigarette lighter nor anything else is connected to a power source. The entire car is stone dead without it.

Also, every time the battery is disconnected, all trouble codes are cleared from the ECU.

LvnTheDrm

Parnelli--

"Search" is your friend. Look for posts that describe setting the readiness codes. I like the BMW drive-cycle instructions (gives specific sequence, speeds, etc in order to "set" the codes). Only important for when you need to get smogged.

Watch out for Stealers (dealers)! Pricing tends to be too high--and many of today's techs actually not well-versed in 15-yr old cars. Best to find local Independent--ideally with Rennlist recommendation.

Enjoy!

ca993twin

Are you sure that's true? The cigarette lighter BECOMES the power source when the maintainer is plugged in... I think. I've also seen devices that will plug into another car's cig lighter to provide 12 V, and the other end is plugged into your OBD2 port. This is supposed to save the readiness codes and the radio code. Since I have neither a maintainer nor a OBD2 thingee, I was thinking of just hooking my cables (very carefully) to my 12V battery charger to keep the car alive while the battery is changed.

MarkD

sorry 'bout that

I'll explain: Most (all?) States require the OBDII emissions system flags to be "ready" before passing a smog test. Some states have lesser requirements... I'm not sure about yours.

Here is a thread on the drive cycle: https://rennlist.com/forums/showthre...ferrerid=35947


The exec summary:
-------------------------------------------------------------------------------------

- The following cycle needs to be done twice -

1. Start engine, idle cold for approx. 2 min, 10 secs.

2. Accelerate to 20-30 MPH, Maintain steady speed for approx 3 min, 15 secs.

3. Accelerate to 40-60 MPH, Maintain steady speed for approx 15 mins.

4. Decelerate and come to a stop. Idle for approx 5 mins (if tiptronic, idle in gear)

Following the start engine phase the sequence of test conditions may interchange.

Routine will be discontinued whenever:

Engine speed exceeds 3000 RPM
Large fluctuations in throttle angle
Road speed exceeds 60 MPH

------------------------------------------------------------------------------------
Sometimes the flags set over time. If that happens, buy a lottery ticket
Only half joking, in my experience some of the flags don't set without the above cycle.

Arena993

^^^^^ Steve this was on the lines of what someone posted

Mike

ShdwFx

I've successfully used a "12V Automotive Settings Keeper" that runs off a 9V battery and plugs into the cigarette lighter when changing out my battery. No issues with losing any radio settings or readiness codes while the battery was disconnected. Link below has one for $8.

http://www.geeks.com/details.asp?invtid=GK504&cat=GDT

911Dave

Well I can't say I'm 100% sure, but I don't see how it's possible. The Porsche battery maintainer only puts out 500mA (half an amp) at full output, and it's not continuous but rather on/off depending on how it senses the charge state of the battery. With no battery connected I can't imagine it would function at all. Also, automotive circuits are all grounded to the negative battery post, so with no battery connected, all circuits are open so there can be no current flowing through any circuit. If it can indeed work, I'd love to understand how. Maybe the chassis would be grounded through the AC plug. I suppose there's no harm in trying it.

Your regular battery charger is a constant 12V source with much higher current output so that might work.

911Dave

That looks like a pretty handy device.