Tire Pressure problem - Software or Sensor?
08-30-2011, 04:42 PM
#1
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Tire Pressure problem - Software or Sensor?
I recently sold my 2002 996 and picked-up a 2008 997 coupe. I am having a blast with it.
Two days ago the computer alerted me that my right rear tire was 4 psi low. I checked it manually and checked the computer display by scrolling through the options - both showed normal rear tire pressure (44 psi as listed in the owner's manual for summer tires). The computer itself displayed a discrepancy - it displayed an alert that the right rear tire that was 4 psi low, but then showed the same tire pressure as normal when I scrolled to the "tire pressure" screen.
I reset the tire pressure system. When it was finished "learning" it reported that my right rear tire was actually fine, but now my left front tire was 4 psi low. I reset it a 2nd time and it changed again, reporting my right front was 4 psi low while the other 3 tires were fine.
I figured this was likely a common problem so I searched this forum. There are suprisingly few posts about the tire pressure monitoring system - at least that I found.
This sounds like a computer software malfunction to me.
It is under warranty, so I figure a visit to the Porsche dealership is in order.
Any thoughts?
Thanks -
3KRAD
Two days ago the computer alerted me that my right rear tire was 4 psi low. I checked it manually and checked the computer display by scrolling through the options - both showed normal rear tire pressure (44 psi as listed in the owner's manual for summer tires). The computer itself displayed a discrepancy - it displayed an alert that the right rear tire that was 4 psi low, but then showed the same tire pressure as normal when I scrolled to the "tire pressure" screen.
I reset the tire pressure system. When it was finished "learning" it reported that my right rear tire was actually fine, but now my left front tire was 4 psi low. I reset it a 2nd time and it changed again, reporting my right front was 4 psi low while the other 3 tires were fine.
I figured this was likely a common problem so I searched this forum. There are suprisingly few posts about the tire pressure monitoring system - at least that I found.
This sounds like a computer software malfunction to me.
It is under warranty, so I figure a visit to the Porsche dealership is in order.
Any thoughts?
Thanks -
3KRAD
08-30-2011, 06:03 PM
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I recently sold my 2002 996 and picked-up a 2008 997 coupe. I am having a blast with it.
Two days ago the computer alerted me that my right rear tire was 4 psi low. I checked it manually and checked the computer display by scrolling through the options - both showed normal rear tire pressure (44 psi as listed in the owner's manual for summer tires). The computer itself displayed a discrepancy - it displayed an alert that the right rear tire that was 4 psi low, but then showed the same tire pressure as normal when I scrolled to the "tire pressure" screen.
I reset the tire pressure system. When it was finished "learning" it reported that my right rear tire was actually fine, but now my left front tire was 4 psi low. I reset it a 2nd time and it changed again, reporting my right front was 4 psi low while the other 3 tires were fine.
I figured this was likely a common problem so I searched this forum. There are suprisingly few posts about the tire pressure monitoring system - at least that I found.
This sounds like a computer software malfunction to me.
It is under warranty, so I figure a visit to the Porsche dealership is in order.
Any thoughts?
Thanks -
3KRAD
Two days ago the computer alerted me that my right rear tire was 4 psi low. I checked it manually and checked the computer display by scrolling through the options - both showed normal rear tire pressure (44 psi as listed in the owner's manual for summer tires). The computer itself displayed a discrepancy - it displayed an alert that the right rear tire that was 4 psi low, but then showed the same tire pressure as normal when I scrolled to the "tire pressure" screen.
I reset the tire pressure system. When it was finished "learning" it reported that my right rear tire was actually fine, but now my left front tire was 4 psi low. I reset it a 2nd time and it changed again, reporting my right front was 4 psi low while the other 3 tires were fine.
I figured this was likely a common problem so I searched this forum. There are suprisingly few posts about the tire pressure monitoring system - at least that I found.
This sounds like a computer software malfunction to me.
It is under warranty, so I figure a visit to the Porsche dealership is in order.
Any thoughts?
Thanks -
3KRAD
Not that you care, but for posterity, the second gen version works fine on the 997.2 which uses more computer bandwidth everywhere. And different sensors inside the wheel so far as I know. I know the system that reads those sensors has changed.
08-30-2011, 06:56 PM
#3
Race Director
44psi hot or cold?
for the 2008 Carrera the COLD tire pressure for summer tires and 2 passengers and light luggage should be 33 front and 39 rear. If you have a Carrera 4 it's 33/37.
44psi rear is only for 4 passengers and full luggage. Reset your TPMS for partial load and summer tires and set you psi cold to 33/39.
for the 2008 Carrera the COLD tire pressure for summer tires and 2 passengers and light luggage should be 33 front and 39 rear. If you have a Carrera 4 it's 33/37.
44psi rear is only for 4 passengers and full luggage. Reset your TPMS for partial load and summer tires and set you psi cold to 33/39.
08-30-2011, 07:00 PM
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44psi hot or cold?
for the 2008 Carrera the COLD tire pressure for summer tires and 2 passengers and light luggage should be 33 front and 39 rear. If you have a Carrera 4 it's 33/37.
44psi rear is only for 4 passengers and full luggage. Reset your TPMS for partial load and summer tires and set you psi cold to 33/39.
for the 2008 Carrera the COLD tire pressure for summer tires and 2 passengers and light luggage should be 33 front and 39 rear. If you have a Carrera 4 it's 33/37.
44psi rear is only for 4 passengers and full luggage. Reset your TPMS for partial load and summer tires and set you psi cold to 33/39.
Gary
08-30-2011, 07:21 PM
#5
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I only had issues with TPMS after tracking. When I had to lower pressure to ensure it doesn't get too high when hot. Usually AFTER sessions when things cooled down I'd get all that pressure warning messages, which is fine.
The probelm was that in some cases even after adding pressure and even when the TPMS itself reported normal tire pressure, the warning remained?! Not sure why? Either software flaw, or maybe it counts the tire heat into equation (doubt it).
I had to either wait for overnight, or reset for warning messages go away.
The probelm was that in some cases even after adding pressure and even when the TPMS itself reported normal tire pressure, the warning remained?! Not sure why? Either software flaw, or maybe it counts the tire heat into equation (doubt it).
I had to either wait for overnight, or reset for warning messages go away.
08-30-2011, 11:05 PM
#6
The tpms in my 2007C2 drives me crazy. I find I need to reset it almost once per week to keep the false alarms away. If it were up to me, I'd have the thing disabled.
08-30-2011, 11:17 PM
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Hmm, that sounds a bit excessive, mine is also 2007 but I've only had to reset it after track days as I explained. Maybe check them out.
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08-30-2011, 11:30 PM
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I only had issues with TPMS after tracking. When I had to lower pressure to ensure it doesn't get too high when hot. Usually AFTER sessions when things cooled down I'd get all that pressure warning messages, which is fine.
The probelm was that in some cases even after adding pressure and even when the TPMS itself reported normal tire pressure, the warning remained?! Not sure why? Either software flaw, or maybe it counts the tire heat into equation (doubt it).
I had to either wait for overnight, or reset for warning messages go away.
The probelm was that in some cases even after adding pressure and even when the TPMS itself reported normal tire pressure, the warning remained?! Not sure why? Either software flaw, or maybe it counts the tire heat into equation (doubt it).
I had to either wait for overnight, or reset for warning messages go away.
The computer reads internal temperature and pressure of each tire and your setting for summer/light-load or otherwise. Then it reports whether you need to add or subtract air to reach the specified pressure.
The owner's manual describes the equation for temperature correction in a simple form, so I won't bother, but basically tires need higher pressure when they're working harder, not less. Run fast or corner hard, and the pressure rises along with the heat in the tire. That in turn reduces the flexing and slows the rise of temperature. If it were the other way around (not that physical laws permit that, just saying), then a runaway temperature rise would occur. Tires are designed around this physical relationship. If you lower the pressure after working the tire, then you're basically doing your best to create that runaway condition. It's unlikely you'll be aggressive enough to succeed, but you're definitely moving the wrong direction when you bleed air.
Even the Michelin field engineers aren't comfortable with working pressures that rise above fifty psi, though I suspect their factory engineers did anticipate those pressures in track conditions. In any case, you should consider doing what the field engineers do and what Michelin corporate recommends: add a couple of pounds to the tires while cold in the morning before a track event. Check them later between sessions and leave them alone unless the pressure gets above fifty psi and stays there for a significant time.
So in a lightly loaded 997.2, we run 34/40 for street work. Michelin recommends going to 36/42 while the tires are cold. Your "tire info pressure" screen will say each tire is +2. If you know what you're doing (as their professional drivers do), you adjust the front to rear balance after the first session, or in advance if you're familiar with the car and type of tire. Otherwise leave them at the higher pressures that track work causes them to reach. The "tire info pressure" will still read +2 even when the gage pressures reach 41/47 or 43/49 or 44/50.
If the high pressures really worry you, then check them ten minutes after each sesson with a compensated gauge. If you see more than fifty psi, wait another twenty minutes and check again. If you still see more than fifty psi, lower both tires on that axle to fifty psi.
I don't necessarily agree with that last procedure, which the field engineers have added to the factory's advice, but there you have it, just as they described it. Your decision in any case of course, but that's what Michelin have recommended.
Someone on this forum mentioned a recommendation in the docs for the new Super Sports that the tires be run at something in the low twenties for track use. I can't find that note and I'd like to discuss the recommendation with a contact at Michelin. If anyone remembers that note, or you wrote it, can you give me more information? I'd love a scan of that documentation.
Gary
Last edited by simsgw; 08-30-2011 at 11:32 PM. Reason: typo
08-30-2011, 11:33 PM
#10
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TPMS is somewhat problematic for some 997.1 owners--solved much in the .2 version.
I have been fairly lucky when I ordered it for my 06. (It became standard in the 911 in 07). However, the delta T way of reporting an air shortage is problematic. I just have it read out absolute PSI for me, targeting 33/39 for my lightly loaded cab.
Read up more within the manual on it. I, too experienced that delta T problem at one time but work with it to eliminate it yourself. The dealerships are usually clueless, unfortunately.
I have been fairly lucky when I ordered it for my 06. (It became standard in the 911 in 07). However, the delta T way of reporting an air shortage is problematic. I just have it read out absolute PSI for me, targeting 33/39 for my lightly loaded cab.
Read up more within the manual on it. I, too experienced that delta T problem at one time but work with it to eliminate it yourself. The dealerships are usually clueless, unfortunately.
08-31-2011, 01:58 AM
#11
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It does in fact take into account the tire heat. That is if you have a 997.2 and I seem to remember you do have, Alex.
The computer reads internal temperature and pressure of each tire and your setting for summer/light-load or otherwise. Then it reports whether you need to add or subtract air to reach the specified pressure.
The owner's manual describes the equation for temperature correction in a simple form, so I won't bother, but basically tires need higher pressure when they're working harder, not less. Run fast or corner hard, and the pressure rises along with the heat in the tire. That in turn reduces the flexing and slows the rise of temperature. If it were the other way around (not that physical laws permit that, just saying), then a runaway temperature rise would occur. Tires are designed around this physical relationship. If you lower the pressure after working the tire, then you're basically doing your best to create that runaway condition. It's unlikely you'll be aggressive enough to succeed, but you're definitely moving the wrong direction when you bleed air.
Even the Michelin field engineers aren't comfortable with working pressures that rise above fifty psi, though I suspect their factory engineers did anticipate those pressures in track conditions. In any case, you should consider doing what the field engineers do and what Michelin corporate recommends: add a couple of pounds to the tires while cold in the morning before a track event. Check them later between sessions and leave them alone unless the pressure gets above fifty psi and stays there for a significant time.
So in a lightly loaded 997.2, we run 34/40 for street work. Michelin recommends going to 36/42 while the tires are cold. Your "tire info pressure" screen will say each tire is +2. If you know what you're doing (as their professional drivers do), you adjust the front to rear balance after the first session, or in advance if you're familiar with the car and type of tire. Otherwise leave them at the higher pressures that track work causes them to reach. The "tire info pressure" will still read +2 even when the gage pressures reach 41/47 or 43/49 or 44/50.
If the high pressures really worry you, then check them ten minutes after each sesson with a compensated gauge. If you see more than fifty psi, wait another twenty minutes and check again. If you still see more than fifty psi, lower both tires on that axle to fifty psi.
I don't necessarily agree with that last procedure, which the field engineers have added to the factory's advice, but there you have it, just as they described it. Your decision in any case of course, but that's what Michelin have recommended.
Someone on this forum mentioned a recommendation in the docs for the new Super Sports that the tires be run at something in the low twenties for track use. I can't find that note and I'd like to discuss the recommendation with a contact at Michelin. If anyone remembers that note, or you wrote it, can you give me more information? I'd love a scan of that documentation.
Gary
The computer reads internal temperature and pressure of each tire and your setting for summer/light-load or otherwise. Then it reports whether you need to add or subtract air to reach the specified pressure.
The owner's manual describes the equation for temperature correction in a simple form, so I won't bother, but basically tires need higher pressure when they're working harder, not less. Run fast or corner hard, and the pressure rises along with the heat in the tire. That in turn reduces the flexing and slows the rise of temperature. If it were the other way around (not that physical laws permit that, just saying), then a runaway temperature rise would occur. Tires are designed around this physical relationship. If you lower the pressure after working the tire, then you're basically doing your best to create that runaway condition. It's unlikely you'll be aggressive enough to succeed, but you're definitely moving the wrong direction when you bleed air.
Even the Michelin field engineers aren't comfortable with working pressures that rise above fifty psi, though I suspect their factory engineers did anticipate those pressures in track conditions. In any case, you should consider doing what the field engineers do and what Michelin corporate recommends: add a couple of pounds to the tires while cold in the morning before a track event. Check them later between sessions and leave them alone unless the pressure gets above fifty psi and stays there for a significant time.
So in a lightly loaded 997.2, we run 34/40 for street work. Michelin recommends going to 36/42 while the tires are cold. Your "tire info pressure" screen will say each tire is +2. If you know what you're doing (as their professional drivers do), you adjust the front to rear balance after the first session, or in advance if you're familiar with the car and type of tire. Otherwise leave them at the higher pressures that track work causes them to reach. The "tire info pressure" will still read +2 even when the gage pressures reach 41/47 or 43/49 or 44/50.
If the high pressures really worry you, then check them ten minutes after each sesson with a compensated gauge. If you see more than fifty psi, wait another twenty minutes and check again. If you still see more than fifty psi, lower both tires on that axle to fifty psi.
I don't necessarily agree with that last procedure, which the field engineers have added to the factory's advice, but there you have it, just as they described it. Your decision in any case of course, but that's what Michelin have recommended.
Someone on this forum mentioned a recommendation in the docs for the new Super Sports that the tires be run at something in the low twenties for track use. I can't find that note and I'd like to discuss the recommendation with a contact at Michelin. If anyone remembers that note, or you wrote it, can you give me more information? I'd love a scan of that documentation.
Gary
From experience I get a lot more problems on track if I start around manufacturer recommended pressure, as it quickly rises to 50 PSI in the rear and I lose a lot of grip. My sweet spot is somewhere between 36/42 and 38/46, if I start 33/39, I definitely go above those PSI, so what I do, I drop 3-4 PSI from cold temps (to be exact from temps I arrive at track, which is 2 PSI higher than morning), then I monitor and adjust after each session.
My TPMS warning messages mostly appear AFTER the track day is over and when tire pressures go down (while I've seen warning of too much pressure on track), my suprise was that the message remained EVEN AFTER I added more pressure to my tires, and checked with my own gauge and EVEN TPMS, so TPMS reading says 33/39, while the "red warning" message remains?! That to me is a software flaw (aparently only on .1), that the warning message is not refreshed quick enough.
08-31-2011, 05:24 AM
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Thanks Gary. I actually have a 997.1.
From experience I get a lot more problems on track if I start around manufacturer recommended pressure, as it quickly rises to 50 PSI in the rear and I lose a lot of grip. My sweet spot is somewhere between 36/42 and 38/46, if I start 33/39, I definitely go above those PSI, so what I do, I drop 3-4 PSI from cold temps (to be exact from temps I arrive at track, which is 2 PSI higher than morning), then I monitor and adjust after each session.
My TPMS warning messages mostly appear AFTER the track day is over and when tire pressures go down (while I've seen warning of too much pressure on track), my suprise was that the message remained EVEN AFTER I added more pressure to my tires, and checked with my own gauge and EVEN TPMS, so TPMS reading says 33/39, while the "red warning" message remains?! That to me is a software flaw (aparently only on .1), that the warning message is not refreshed quick enough.
From experience I get a lot more problems on track if I start around manufacturer recommended pressure, as it quickly rises to 50 PSI in the rear and I lose a lot of grip. My sweet spot is somewhere between 36/42 and 38/46, if I start 33/39, I definitely go above those PSI, so what I do, I drop 3-4 PSI from cold temps (to be exact from temps I arrive at track, which is 2 PSI higher than morning), then I monitor and adjust after each session.
My TPMS warning messages mostly appear AFTER the track day is over and when tire pressures go down (while I've seen warning of too much pressure on track), my suprise was that the message remained EVEN AFTER I added more pressure to my tires, and checked with my own gauge and EVEN TPMS, so TPMS reading says 33/39, while the "red warning" message remains?! That to me is a software flaw (aparently only on .1), that the warning message is not refreshed quick enough.
Telemetry is a tricky business that we used to use pretty hefty computers to manage. Basically, I know squat about the first-gen TPMS, but I agree that it sounds like a disconnect between the coder's mental image of how we would use the system and how we actually do. Maybe not quite as bad, but in the spirit of the Japanese air conditioning systems until American Honda took an incoming delegation to the airport parking lot and made them get into their own cars that had been sitting in the San Antonio sun for two hours. Japanese air conditioning improved wonderfully by the next generation. Or so the story goes.
Could we park some German engineers next to a gas station air compressor and dare them to set the pressures on a 997.1? In the sun? After a track day?
Gary
05-21-2012, 12:20 AM
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I have a 997 2007 carrera s, the TPS is like freeze, and the warning light is always on, only show the presure of the right side, but is not the presure isnlike freeze, in the dealer posche the told me that in the scan do not appear nothing and told me that maybe isbthe battery ofbthebsensors, i imported 4 new sensors (i am in peru) but nothing change, somebody have an idea ofbthe problem, thanks for ypur comments.
05-21-2012, 10:27 AM
#14
Instructor
I had a problem on my 2008. It first starting giving a false flat tire warning then it would correct itself. Next time it would claim it could not connect to a sensor, sometimes one, sometimes all four, then mysteriously while driving it would usually clear itself, etc, etc. I did all the re-set, re-learn stuff to no avail. The dealer ended up replacing the TPMS control module (under warranty).
05-21-2012, 11:25 AM
#15
Drifting
I had a problem on my 2008. It first starting giving a false flat tire warning then it would correct itself. Next time it would claim it could not connect to a sensor, sometimes one, sometimes all four, then mysteriously while driving it would usually clear itself, etc, etc. I did all the re-set, re-learn stuff to no avail. The dealer ended up replacing the TPMS control module (under warranty).
