upier

So I've been getting a TPMS warning the last couple of days. I do a reset and it holds until I turn off the car. I did a reset on the way to work. After work I got the warning again. It showed that the left rear was -5. I looked at the pressures and the system 30/30 37/37. After the short drive home system showed 33/31 39/39. The warning screen showed -4/-5. -5/-4. Physical checked showed 33/32 40/40. So is this bad TPMS(s) failing or a bad TPMS module? Car is a 2011 C2S 997.2. Thanks in advance.

mike cap

Going from memory the owners manual calls out 37F 44R for cold fully loaded.

Partial load is 34F 38R cold. From memory again.

You can reset the program for partial load and the TPMS will use these readings as a baseline.

Your actual pressures may be low enough when the program is set for a fully loaded car to trip a warning.

I have been running 34F and 38R with a "partial load" setting.

8202632

Sounds like the bAttery in the tpms

OKB

I think they are too low, put 36 cold all the way around and see how it behaves

upier

Okay I just went out and put air in the tired. Set them to 35/42. Set system to partial load. Well see if the error returns in the morning. The set cycle finished in about two miles. No error when I turned it off so a good

patriot993

I have been having system give me an error that 1 or more tires is -4. I have physically checked the tire pressure and it is fine. I reset the system and it is fine for a day or two then I start getting errors again. I assumed it is the TPMS batteries...just procrastinating on fixing it. My guess is that your error will return

911Finally

Your problem may be what mine was. I have a local Costco near me that has an outside air hose. Actually might be nitrogen or nitrogen/oxygen mixture as the hose is green and Costco fills their new tires with Nitro. Their meter is also digital to you know you're filling to the correct amount. Anyway I was getting errors that I was low on all my tires and I know the pressure was good. I was filling to 37F and 44R as stated on the door jam. I've been doing that for almost 2 months since getting the errors. it would last maybe half hour before getting new errors. I hadn't noticed the sticker on the meter that said "Fill warm/hot tire an extra 4 pounds. A warm tire is a tire driven aprox. 1 mile." So I filled to 41F and 48R and all has been fine in the 2 weeks since I've done that.

OKB

I dont know what the decal says, but I think you missunderstand what it says. A cold tire pressure like 36 lbs will go up 4 to 5 lbs when tire gets hot. So if you have 36 cold, it is really 40 ,41 lbs hot when driving the car
Also you can go to any tire shop and they have a tpms reader that tells if the sensor is sending the right amount of signal, they just walk to each wheel

911Finally

Maybe I'm still misunderstanding. But if I pull to the pump my tires are now hot. I put air in them and they are still hot. It says to fill 4 pounds over on hot tires. So when I get home with my hot 41 fronts, they will cool down to 37 which is what the cold tire pressure should be, no? Am I still missing something? I'll take a pic of the decal on the pump when I'm there again.

Bwk02

Had the same issue
Had to keep resetting it


Decided to change one of the settings/assumptions from 18 inches to 19 inches (tires are actually 18 inches)


Have not received an error yet


Not truly a 'fix' per se, but I am glad to be rid of that constant '!' on the instrument cluster

OKB

you are right, but Im not concerned what a decal on the air pump says,It is miss communicating in some way. I thought you were saying it was a decal on your car.

semicycler

Lot's of different issues here, some more accurate than others. I just retrofitted TPMS into my 2006 so here's what I know.

The sticker on your door jamb lists full load tire pressures. This is for two passengers with full luggage in the frunk. For my 2006 C2S with 19" wheels it lists pressures as 37F/44R. These are the FULL LOAD target pressures. Your year/model might be slightly different so check your users manual.

Most people do not drive at full load, instead it's a single driver or perhaps two people without luggage. This is considered partial load. In the majority of cases performance of your car is better using partial load pressures. My 2006 C2S lists partial load pressures in the owner's manual at 33F/39R. These are the PARTIAL LOAD target pressures.

So pick one target for your car and use it, either full load or partial load. Most cases partial load will be better for you.

Now this is where the TPMS system comes into play. You have to tell the car which target pressures you have setup your car with - match the computer to the targets you use. If you run partial load pressures but tell the TPMS system it's full load, then the TPMS system will think you are underfilled by -4 or -5 psi. It's the difference between full load and partial load targets. The reverse can happen too although I don't think it throws a warning - using full load pressures but telling the car it's setup as partial load. The TPMS system will think you are 4 or 5 PSI over the target.

On the steering column there is a stalk to control the onboard computer. Go into the TPMS menu and setup the tires installed on your car - summer or winter, 18" or 19", partial or full load. This will clear most of the TPMS warning messages.

The next error people will see is if the batteries in the tire sensors are near their end of life, usually in the 4 to 6 year old range. In this case the sensor will randomly read the wrong pressure or no pressure at all, telling the TPMS control unit that your tires are at a different pressure than reality. Unfortunately the TPMS control unit corrects the absolute pressure reading from the sensors based on temperature. So the reading displayed might not match the same reading you get from a separate tire gauge (it reads absolute pressures, not temp corrected pressures). But when the tires are cold - normal ambient temperatures - the control unit and a separate accurate tire gauge will read very close to each other. Not positive but I though the nominal cold pressure was 68 deg F. In my case my brand new wheel sensors read within 1 psi of the actual tire pressure from multiple separate tire gauges when cold.

So if you are seeing no reading, readings that bounce around, or more importantly one or more corners acting up and the tire is not flat, then it's more likely a battery issue. If all your tires read about -4 below what it thinks it should read, you probably have your pressures set to partial loads but the computer thinks you are running full load targets.

And for the advanced, it's possible to configure additional tire setups with PIWIS - 17" wheels, and "special" tires. With the special tire you define the target pressures. So if you run track tires or purposely lower your street tire pressures before hitting the track, you could define the "special" setup in the TPMS control unit and set the pressures to your targets to eliminate any TPMS warnings of low pressures. Or just disable the TPMS system entirely.

upier

So an update. I filled the tires and reset as described above. This morning I got no warnings. So I guess I was too far below the partial load pressures. I suspect that the system doesn't perform well at pressures much below 32 psi. I'll keep monitoring. Sensors are getting old.

mike cap

So all the good advice I read was helpful to you? That's good to know.

stevepow

My setup (997.2) used to allow me to select Load (Partial or Full) as well as 18's or 19's but after I installed the Sport Classic wheels, I don't get those options anymore - I can choose Summer or Winter, but get no other options. The dealer had to install a new TPMS controller when I had those wheels put on, so I'm not sure what they did - incorrect coding or what. Another thing to bring up at the next service I guess.

Additionally, the pressure readings I get always have been the actual pressure, not temp corrected - if it says 42, it is 42 and always correlates closely with a digital gauge. However the Delta from target readings, +1, 0, -2, etc. are temp corrected - in other words if I leave the house and the rears are 42 with a Delta of 0, after several miles they may now indicate 46 because they have heated up, but the Delta from target is still 0.