When I start my DB9 on the first cold day every fall it greets me with a scary “Check Tires” tire warning alert on the instrument cluster. In frustration and alarm about all I can think is “Now what!”. As it turns out this hasn’t been a big deal.
When the ambient air temperature falls, air gets denser. Consequently, this causes the air pressure in a cold tire to drop slightly. In our DB9’s, if the pressure drops below 30 psi the alert will trip the Tire Pressure Monitoring System (TMPS) to warn you of a potential issue. A small pressure change isn’t the end of the world, but we need to follow up. You can learn more about the TPMS system and what will cause an alarm in my more detailed article here.
I check the pressure in my DB9’s tires a few times each year, and when I set them in the summer the ambient air temp is usually 85+ degrees. In the fall where I live (Northern California) the ambient temperature can drop to below 40 degrees, a 45+ degree change. This appears to be enough of a change to trip the alert each fall.
The next logical step is to get out of the car, open the trunk and look at the brains of Tire Pressure Warning system mounted along the top. There are five (5) colored LEDs on the device, and you should discover at least one lit up solid and the rest blinking. The one that is on solid is the one with a pressure problem. In this occurrence on my car it was the Red LED that was solid (meaning the left front tire had an issue). Each color corresponds to a specific wheel (that’s that those little colored bands are around the tire valve stem). 
They are:
- Yellow – Left Rear
- Red – Left Front
- Green – Right Front
- Blue – Right Rear
[Note: My car is a 2005, and later model cars may have a more integrated TPMS system, or even just tell you which tire is low and its pressure. Early model owners need to follow this more manual approach].
Once you know which tire is alerting, grab your tire pressure gauge and check the pressure of that wheel (you can check out my other article on how to do this). If its below 30 psi, you can confirm this is the problem tire. Personally, I would recommend you check all four tires while you are at it since the others will likely be close to the same issue.
The solution now is to top up your tire pressures. If you have your own compressor just add air to reach the ideal pressure of 36 psi in the fronts and 38 psi in the rears. If you don’t have a compressor, and the tire is just down a couple of PSI, you can still drive safely to the nearest gas station and top of your pressure there.
Once you’ve topped up the pressure back to normal, the alert should clear. You may need to turn off the car completely and start up again for the TPMS to recognize the issue is resolved and clear the alert on the instrument cluster.
Warning: If you top up the air and the problem returns quickly on the same wheel, this is likely not because the outside air temp has dropped and you may have a puncture in the tire. Time to take the car to a tire repair specialist immediately. Don’t drive on a tire if the pressure is below 20 psi. Don’t drive very fast or very far either or you risk damaging the core of the tire and it will need replaced (at significant expense since they have to be done in pairs). And I wouldn’t use the can of tire repair ‘Goo’ in the toolkit of the Aston unless I was desperately stranded roadside. That Goo may solve the problem temporarily, but you’ll be messing up the inside of the tire, the TPMS and the wheel rim. My tires have been ‘Screwed’ a few times, check out this article.
Video
Here is a quick video of the experience I recorded on one of those days….
Aston 1936 
My 2005 DB9’s TPMS warning light control box is located underneath the passenger side glovebox.
LikeLike
Hmmm. I wonder when they relocated this, and if yours or mine is the newer approach. My car number is 1936. What is yours?
LikeLike
03293
06/05
LikeLike
02893
05/05
TPMS in trunk.
BIG fan of your site. Can not thank you enough for all the effort you have put in Steve.
LikeLike
Thanks for your car number. Since David’s is car no. 3293 and is in the glove box area, and my 1936 and your 2893 is in the boot, the change happened sometime in the 400 cars between your two. I guess under the dash is the later model arrangement.
Funny, the boot seems like a better spot.
LikeLike
I wrote my VIN number and I think we can narrow it down to 40 cars. I have learned that the last digit in the VIN number is a check sum/number of all other numbers. Correct me if I am wrong. Yes, I know, I am a nerd, haha
By the way, the build number on my car is the same as the last four digits in my VIN number. I am thinking of the article about it on Your car. 1906/1936. Was the parts on Your car originally intended for another car at the factory. Strange? Did they make a last minute swap at the factory?
I guess, among other things, this is what gives Astons the SOUL…
LikeLike
As a 2009 DB9 Owner, my TPMS unit is also under the passenger side dash. However, I had one faulty sensor and the cost of replacement was beyond the pale. Instead I bought this aftermarket TPMS unit: https://www.amazon.com/Orange-Monitoring-Transmitter-Diagnostic-Temperature/dp/B0111PVHR2/ and then bought this bypass harness to fool the OEM unit and turn off the dash light: https://www.redpants.lol/shop/tpms-fault-defeat
All in for under $200; half what one OEM sensor would cost from Dealer. The bonus is I now have psi and temp readouts with audible warnings you set at your discretion.
LikeLike
Hi Dave. The additional data sounds great. I presume you have a completely separate TPM brain wired in somewhere with all that data available.
I have an article coming on replacing the TPMs, mine died and I took it in the A$$ from the dealer. Chalk it up to learning experience, and it will make an interesting pair of articles.
LikeLike
Stand alone receiver about the size of a garage opener remote. Plugs into cig lighter but they recommend hardwiring to a switched power source for long term use. Presently my cig lighter is HOT so I plug it in for the ride then unplug when done. Considering I only checked pressure manually in my other cars once a week at best this is very convenient. I liked this setup so much I bought one for my Ferrari 360 which had no factory TPMS system.
LikeLike
It looks pretty trick, I was checking it out on Amazon. The price is ridiculously cheap. Would be nice to find a subtle way to mount it, or keep hard wired in glove box until you pull it out when it starts beeping, etc. Nice find!
Another option is the Autel replacement sensors, and they can be ‘cloned’ to match the old sensors ID, and it just replaces the single failed Aston sensor without any dealer programming, etc. This would be just a single wheel repair, and keeps all the original stuff working. Of course, you don’t get all the neat new data.
LikeLike
I tried 3 sources to replace a single TPM Sensor and ultimately no one could despite they all saying “no problem”. That would be great if you can make it the Autel work and document the part #’s and process.. I believe the later OEM units like my 2009 differ from your 2003. One regret about the Orange unit is the power cord comes out from the side making it awkward to mount in a pleasing manner but the glovebox idea has merit.
LikeLike
Hi Steve,
A very informative website – keep it up!
As far as I am aware, the boot-mounted (trunk-mounted) TPMS unit is on the coupe’s, and the volantes it is under the dash on the passenger side (like mine)
Cheers from the land of warm beer and Aston Martins!
Mike.
LikeLike
Hi Mike. Thanks for the kudos and the tip on the TPMS controller location. Makes sense that they moved it inside.
LikeLike