jw1977

Since I can't get my TPMS light to not go off i'm going to increase my cold tire pressure 36front 42rear. Is this okay? I doing this because the TPMS sensor reads 3 pounds lower than my guauge and i'm guessing this is why sensor is going off although I don't know why it's taken 6 months for this to start occuring.

GSIRM3

That shouldn't be a problem. I run the partial load pressures in my C2S, but I think the full load pressures are 37f and 44r, so you are below those pressures.

Are you sure you don't have your TPMS set for full load? If you have it set for partial, then it shouldn't be going off with the pressures you currently run. Are you checking your pressures cold?

texas911

Get a new gauge, my TPMS is spot on with my gauge.

awilks

My TPMS has been 2lbs low on each tire since my car was new. 5k miles and I've tested a couple of different guages with same readings. As previous post mentioned check and make sure your default TPMS setting isn't set for full load which I've not done so will refer you to the manual.

Dariof

The difference between the sensitivity of the TPMS between partial and full load is only 1 PSI.

My TPMS was a PITA.

I finally purchased the least expensive tire pressure gauge (I had been using these high end digital gauges) and inflated my tires to 36/39 cold using partial load. Although the TPMS reads 34/37 cold, it does not default any more.

Try a different gauge
Select Partial Load
Inflate 36/39 minimum
Don't get this option again!!

Dariof

Or maybe the new gauge is off.

mdrums

This is exactly why I did not get TPMS...my dealer really gave me excellent advice on this. I have a very accurate digital gauge and cold on a 68-70 degree day in my garage I sent the tire pressures to 33f/39r as per the Porsche manual. For track days and AutoX this is to much as the tires get hot and pressure buildes the get greasy/spliery feeling.

After talking to the Porsche regonial manager and the teachers at the Porsche Sports Driving School and from the DE track days I have been doing I would never run the max full load pressures unless I had a ton of luggage a heavy passenger and some kids in the rear seats.

wdonovan

And this somehow means that they are both accurate? Or that his gauge is off but his tire sensors are on? Or that your gauge and sensors aren't off by the same amount?

GSIRM3

Why would the "sensitivity" of the TPMS be any different between partial and full? I can see why the reference pressures would be different for full vs partial, but do not understand why the sensitivity would be any different.

The manual clearly states the difference in pressure between that measured by the TPMS and the reference pressures (partial or full) that will cause the alarm. I think it is 4psi differential between the reference pressure and the actual as measured by TPMS. So unless the reference pressures in the computer for the different loads are not what Porsche recommends, which doesn't make sense, then there will be more than 1 psi difference in the alarm settings for partial and full load pressures. For example, the partial load rear pressure is 39 psi and the full load is 44 psi for the 19 inch tires. Why would the TPMS be set up for only a 1 psi difference?

My 997S is a 2007, so the TPMS is standard. I never use it to actually measure the tire pressures. I always use a good gauge to check my tires when cold. For me, the TPMS is just a back-up to let me know if I have a tire loosing air while I am driving. My experience is that the TPMS on my car reads about 2 psi lower than the actual pressure as measured by several gauges I have. My guess is that the system is set up to read about 1 or 2 psi low. Porsche doesn't want to get sued over someone actually using the TPMS to measure the pressure in the tires, then have one blow because of low pressure. They would rather have it read a couple pounds low and have the customer over inflate the tires by a couple psi.

texas911

I use my digital gauge on 2 other cars with TPMS and they are all accurate. Its just a cheapo Accutire digital but it self calibrates every time you use it. I find it better than the mechanical gauges I've used.

Bob Rouleau

On the 997 GT3 there is a learning mode to allow you to set you dsire pressure. Is this unique to the GT3? It is set from the onboard computer.

GSIRM3

I have only had my C2S for three weeks, so I am still learning the car, but I do not think you can set the desired pressures on the TPMS for the 997 or 997S, other than selecting either partial load of full load conditions. There is a "learning" function on the 997 TPMS where the system "learns" the wheels and tires after wheels and or tires are changed. After you go into the "Set" menu to tell the computer the type (summer or winter) and size of tires, it goes through a brief learning period. During that short period of time (only when car is moving) you get a message that the TPMS is inactive and in learning mode. Usually in a couple miles, the TPMS returns to "normal" mode and gives readout of tire pressures. But again, i think the only desired pressures you can set are the programmed partial load or full load pressures. The TPMS then checks actual pressures vs those reference values.

Edgy01

My TPMS works perfectly. It's very close to my Porsche-supplied TP gauge. I run 31 front and 36 rear cold which is precisely what the factory put in them. They warm up to about 34 and 41 or so. Tire wear is even across the tread,--and I've subjected to everything from modest cruising to 180 mph on the autobahn. Talk to your service rep about not extinguishing the light.

jhbrennan

If only we could - TPMS is not an option any longer - I think the feds have mandated it be on all cars.

texas911

Yes TPMS is Fed mandated because of the Ford Explorer Firestone debacle. But its a good thing to have IMHO because the 997 doesn't have a spare.