TPMS Warning Light Lying to You? Here’s Why” – Northcap

Got called out to a member who’d just had her summer tyres fitted. She reckoned something wasn’t right — said the pressures weren’t calibrated properly. That’s actually more common than you’d think. What usually happens is the wheels get rotated, but the TPMS (Tyre Pressure Monitoring System) still thinks each wheel is in its old position.

Bottom line: she had a visibly soft tyre on the rear, but the dash was warning about the front. That’s a classic TPMS mislocation.

She asked if I could recalibrate it — not a problem. Most cars let you do this manually, no fancy tools needed. Typically, you go into calibration mode via the driver’s display. Then, starting at the front left, you drop a bit of air until the horn chirps — that’s your signal. You repeat the process: front right, rear right, and finally rear left. After the last one, the horn gives a double chirp to say job done.

The only hassle? Now you’ve got to pump all four tyres back up again. Not exactly ideal.

Luckily, I carry a few TPMS tools. In this case, the car was an Arcadia. To kick off the calibration, you turn the ignition on, then press both the lock and unlock buttons on the key fob at the same time (this particular model). You’ll hear two chirps from the horn — that means the car’s ready to learn.

Next, I use my TPMS tool — hold it next to the tyre, close to the valve stem. The tool pings the sensor. Once a wheel’s done, hore chirps and a lamp at the next corner lights up to guide you along. Sequence is always the same: front left, front right, rear right, rear left, like you are walking around the car.

After the last one, you’ll get a final double beep — job’s Oxo.

If you drive a GM, grab one of these little TPMS reset tools—just press it near each valve after a tyre rotation and it re-teaches the system. Quick, cheap, and saves a trip to the dealer.

One more member sorted, and a smile on her face.

Tyre safety matters more than most people think

Your tyres are the only thing keeping you in contact with the road—literally four hand-sized patches of rubber doing all the work. That’s why I never ignore a TPMS warning, even if it turns out to be a false alarm.

Under-inflated tyres can wreck fuel economy, increase stopping distance, and cause the sidewalls to overheat—especially dangerous at motorway speeds. Over-inflated ones? They wear unevenly and reduce grip, especially in the wet.

Here’s a quick tip:

Check your tyre pressures once a month (not just when the light comes on). Do it when the tyres are cold—first thing in the morning is best. And don’t go by the number on the tyre sidewall. Use the PSI rating on the door sticker or inside the fuel flap. That’s the one the car’s designed for.

Also, keep an eye on tread depth. Once you’re under 3mm, wet grip drops off fast—long before you hit the legal limit.

And don’t just glance at the outside edge. Modern front-wheel-drive cars love to chew up the inner shoulder, so while the tyre might look fine from the outside, the inside edge could be down to the cords. Always check the full width of the tread—what you don’t see can catch you out.

TPMS is smart tech—but don’t let it replace good habits. Check your pressures, eyeball your tread, and rotate those wheels regularly. Your tyres will last longer, your fuel bill will shrink, and your car will stay safer.

– Northcap

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