Last month, I noticed the Tire Pressure Monitoring System (TPMS) warning light turn on in my 2007 GMC Yukon Denali. When I pressed the button on the dash to see my tire pressures, the left-front tire showed nothing… meaning the computer wasn’t getting any data from that wheel. After a few miles, it started working again, but I kept an eye on it. Every couple of days, it would fail again, and show a warning on my dash, like this:

Your car’s tire pressure is one of the most important factors relating to safety, ride comfort, and even gas mileage. Usually, when your TPMS dash warning light comes on, it’s telling you that at least one of your tires is low on pressure. That’s a great time to check your tire pressures and re-fill as necessary, or drive by a local tire shop — most of which will perform an air check (and even reset or re-calibrate your TPMS sensors) for free.

However, when a warning like “Service Tire Monitor System” appears, you know it’s something more than simply a little more air in the tires will fix. My educated guess was that the batteries in my left-front wheel’s TPMS sensor was dying. And since all four wheels have identical TPMS sensors, all of which were likely installed at the same time, I knew that the batteries on the other three wouldn’t be far behind.

Unfortunately, you can’t just swap out the battery in your TPMS sensor. A TPMS sensor includes the battery, pressure sensor, wireless transmitter, and the fill valve for your tire, all in one unit. Here’s what an average TPMS sensor looks like:

TPMS Sensor

and here’s what one looks like installed on wheel with the tire removed:

A TMPS sensor installed on a wheel with the tire removed.

As the wheel rotates, and as the sensor passes near a receiver in your wheel well on every revolution, it transmits the current pressure to your vehicle’s on-board computer. As the battery in the sensor gets weaker, those transmissions become less powerful, to the point where the system can’t “hear” them any more. On average, a TPMS sensor’s battery should last between 5-7 years. They shut off when not in use, however, so the more you drive, the faster they’ll die.

Of course, your local car dealer wants you to bring your car to them to replace the TPMS sensors. Depending on your dealership, expect to spend between $150-$260 per wheel to have them replaced. Taking mine to the local GMC dealer would have cost me over $800.

Your next best option is a local tire shop. They carry a large assortment of TPMS sensors and will almost certainly have one that is compatible with your car’s TPMS system. The local shops I called (Big O, Discount Tire, & Les Schwab) wanted around $80 per sensor, which included installation. That’s already a big discount over the dealership, and not a bad way to go.

But I’m never satisfied with just a big discount.

I like massive discounts.

So I looked up the TPMS sensor OEM part number for my 2007 GMC and found (without any surprise) that the same sensor is used on nearly all GM’s trucks and SUVs of that era: Cadillac Escalade, GMC Yukon, Chevy Suburban and Tahoe, etc. The OEM sensor (made by AC Delco) had an MSRP of $72.44. Local auto parts stores sold decent quality non-OEM replacements that were compatible with my vehicle for between $52 – $62 each. Alright. Now we’re getting warmer.

But to my surprise, I found these AC Delco OEM TPMS sensors for my GMC Yukon — the exact same ones the dealer would have installed — on Amazon.com for $27.29 ea (including free shipping). So for $109.16, I had all four sensors in my hands within 2 days. I was concerned that maybe they’d be used, or somehow not as advertised. But they arrived brand new, in two days, in the original packaging:

AC Delco OEM TPMS sensors for my GMC Yukon

My next move was to call the local tire shops to get installation quotes. Big O wanted $16 per tire to install them. I told them that sounded a little steep, but they were quick to inform me that it also included “reprogramming them to work with the car.” I had to bite my tongue so as not to reply “Oh, you mean the complex reprogramming method of holding down the lock and unlock buttons on my keyfob for 5 seconds?” Instead, I just thanked them and called the Discount Tire that’s about 3 miles north of me. They quoted me $12 per tire, and said it would include rebalancing. That sounded better, but I still wasn’t satisfied. So I called the other Discount Tire shop that’s 3 miles south of me and talked to Nate. Nate told me it was a “super easy install” and that he’d do it for $20. I asked if that was “per tire.” Nate said “Nope. $20 total.” I asked about rebalancing, and he said they probably wouldn’t need it, but if they did, they’d just do it. I immediately made an appointment for the following morning.

When I checked-in at Discount Tire for my appointment, and dropped my four TPMS sensors on the counter, the guy checking me in asked me where I got them. I told him I got them for $27 each on Amazon. He looked shocked, and told me that they sell them for $60 each, which is close to what they pay for them. I told him that maybe they should start buying them on Amazon! 🙂

Thirty minutes later, I drove away with my new TPMS sensors installed (they did end up rebalancing the wheels). True to their word, Discount Tire only charged me $20 (plus $1.35 tax). I also asked for the old ones so I could include a photo of them in this blog post:

TPMS sensors installed for $20 at Discount Tire

As it turns out, the old sensors weren’t the original ones that came with the vehicle. The previous owner of my Denali had installed aftermarket wheels, and installed these Schrader-Bridgeport TPMS sensors (which cost around $62 online) with the new wheels. I checked the date code on the sensors, and they were manufactured in March of 2009. That means they lasted for a little over 5.5 years, which is average.

So if your “Service Tire Pressure Monitoring System” warning light comes on, and simply refilling your tires up to the proper pressures doesn’t fix it, you don’t have to take your car to the dealer (unless it’s under warranty, in which case, go to the dealer). If you want to save some money, go to a local tire shop instead. And if you want to save a lot of money, look up the TPMS sensor’s part number for your vehicle, buy them on Amazon, and get them professionally installed for cheap. My grand total for parts and installation of four new TPMS sensors was $130.51. That’s less than your dealership will probably charge you to sell you a single sensor… without installation.

Oh, and my daughter and I downed a couple free bottles of water at Discount Tire, too. 🙂

P.S. A high school friend of mine (who has worked at dealerships) pointed out on my Facebook wall that sometimes your dealership will welcome the opportunity to match the local tire shops. So when you call around, include your local dealer(s), and give them an opportunity to “meet or beat.” Sometimes it’s worth it to them just to get you back in the door!

P.P.S. If you have an older car that doesn’t have TPMS, but you’d like to add it, consider a retrofit kit like this from Schrader. Your local tire shop will probably give you a good deal on installing something like that, too.