nelsgood

On startup, the rear sensors on my '07 C4S give erroneous readings until I've driven several miles. They then appear to function normally. Are there batteries in the sensors and if so, can they be replaced or do I have to get new sensors?

Thanks

Mike in CA

TPMS sensors do have batteries but they are designed to typically last 7-10 years. Seem odd yours would be expired after just 3 and besides if they were exhausted, why would they start to work again after several miles? Also, it seems strange that both rear sensors would fail at the same time.

What kind of "erroneous readings" are you getting? Have you checked your pressures manually? Is it possible that the tires are warming up over several miles, pressures rise and come into the acceptable range, and at that point the system behaves normally?

nelsgood

Hi Mike,

I get indications that the driver rear tire is about 7psi low and the passenger tire as much as 30psi low. I've checked the pressures manually and they are correct. I've also re-initialized the TPMS system, but the problem persist.

Edgy01

I would not suspect the batteries on a MY07 car. I'm still running well with my May 06 car (with TPMS) with no problems whatsoever.

Mike in CA

Strange. Seems unlikely both rear sensors would fail at the same time. Might be a fault in the system receiving the signals. A trip to the dealer may be in order; hopefully you are still under warranty.

Frino

[QUOTE=Mike in CA;7928659]TPMS sensors do have batteries but they are designed to typically last 7-10 years. QUOTE]

I've read that the TPMS sensors need to be replaced after 4 or 5 years. My TPMS has been acting up lately with "tpc inactive" and slow to register individual tire pressure readings. I followed fellow rennlister advice and pumped a few pounds of air in each tire and reset the TPC and the TPMS readings eventually returned to normal.

I've assumed, perhaps incorrectly, that all four of my tpms sensors need to be replaced as my 911 hit the dealer's lot in 11/05.

Can anyone confirm that the tpms batteries last 7-10 years?

Mike in CA

I googled the topic before my initial post and found references that said the lithium ion TPMS batteries lasted up to 10 years. One reference said 5-10 another said 7-10. Obviously a pretty wide spread. The OP's car is 4 years old. Not only did it seem too soon for battery failure, but it seemed odd that both rear batteries would be failing at the same time. But who knows?

TPMS hasn't been around that long. Maybe a good baseline hasn't been established yet for how long they last, and perhaps it may even vary from application to application.

RonCT

Beru makes them and the battery is sealed within the unit - so to change the battery means changing the sensor (not the stem). 7 years is the lifespan from my memory of researching this in the past. The Gen 1 system was never known for accuracy, though I've found the Gen 2 on my 09 to be very quick and accurate.

http://www.beru.com/english/produkte/tss.php

Hella-Buggin'

Interesting, I just took my 06' into the dealer today because of an inactive TPMS system. They said the batteries were dead and I need to replace all four sensors. They said the batteries usually last about 4-5 years.

ADias

Can you fit the new sensors coming in the 997.2 gen?

Pugnacious

I had the left rear replaced for erroneous readings due to low battery while the car was still under warranty. I had the right front replaced last week (car is now out of warranty) to the tune of $220.97 (parts and labor) for erroneous readings due to low battery and I was told when I picked up the car that the left front and right rear are showing low battery but are still functioning properly. The production date for my 997S was July of 2006.

Mike in CA

Well, looks like we're getting some interesting data points from Hella-Buggin' and Pugnacious. Based on their experience, it would seem the OP might be having a TPMS battery issue after all.

LlBr

BTW, think about it if you haven't already; we expect a lot from those poor sensors (electronics and batteries) which live a Hellish life. Lots of pressure, moisture and temperature changes.

Fin Fever

maybe try to re-link your tpms transmitters to the system, just like you would do if you replaced the sensor. the transmitters might not be reliably communicating with the recievers and there is a chance that re-linking would improve that.

Edgy01

I may have to consider ordering a set from Sunset Porsche just to be ready for their imminent failure!