[Stevie J]

Hi, I've just bought a 2016 Diesel i30 and the front nearside pressure warning came on. After pumping it up, eventually it went out.. for a day or 2. Now I have both front tyre warnings, despite them being the correct pressure.
I have tried driving at 50mph for a while, deflating them to 9psi then re-inflating but not luck. The car has sat largely dormant for a good few weeks, should I try a long drive or should I get the sensors replaced? Is it expensive, can a tyre dealer do this? Sorry for so many questions.. Many Thanks

[pidim]

Would it be the sensor battery?   For a 2016 car it's probably that, given they last around 5-7 years, I believe. 

[Stevie J]

Ah now there's a thought. I think I'll try that first, thank you.

[TerryT]

As pidim posted, TPMS sensor batteries can usually last about 5-7 years, depending on brand quality. Bit of a coincidence that a battery sensor fails on one tyre and then just two days later another one fails, but it is possible. BTW, the batteries are considered non-replaceable so it's a new sensor or nothing.

I would take the car to a quality garage/tyre specialist with a TPMS tool which they can connect to the tyre valves of your two problem tyres and read whether the sensor batteries are OK. (It's either a Good or a Bad battery reading, no in-between). If the batteries have failed on the two tyres, I would replace all four sensors as it will only be a matter of time before the other two fail.

The purist techician will use a special low range torque wrench to tighten the sensor nut to the rim and tighten the tyre valve in the stem but others will rely on their years of experience etc.

[TerryT]

Correction to my post above. The TPMS tool is not physically connected to a tyre valve, the tool is just held against the valve stem or against the tyre wall at the valve stem position. (I was distracted by watching TV while typing my post on a my tablet and was not concentrating enough and thinking of another tool). 

[TerryT]

@Stevie J.  Any update on what the issue was?

[Stevie J]

My local garage reset the warning with their software, and pumped the tyres up 2psi above the recommended, which they say they do to all Hyundai cars.. So I never really found out what caused the fault, as the sensors were not replaced.. All good (for now) .

[TerryT]

OK. Bit of a mystery. Thanks for the update.