Doctor Diesel

Light pollution

Hi Doc

I have a 2017 Focus, and back in 2021 it started to show a warning light for tyre sensors not detected. After being reset, they did not come on again for a few days. Gradually the warning started to come on more and more, until it appeared every time the car was driven and approximately every 15 minutes.

At a visit to my local Ford dealership, they said that three of the sensors were faulty and would need to be replaced. I had all four sensors replaced and guess what, on the way home from the garage, the warning light came on. I have been back to the garage so many times with this fault, I have lost count and they have given up trying to fix it. To put out the light you have to reset it every time.

About six months after the sensors were replaced, the warning stopped coming on and this lasted for approximately seven months. The fault is now back, but when the orange tyre warning light comes on it goes out again after about 10 minutes. Driving for another 15 minutes, it comes on again and stays on until the car is parked for at least 2 hours, and on start up the light is gone.

The warning comes on every time I drive and is very distracting. Have you any idea what could be causing this problem?


Ken Stevens

Hello Ken,

This one had me scratching my balding cranium, so I got in touch with a Kent-based Ford servicing and repair specialist called Claremont. One of its technicians described the system fitted to your car (which incidentally is a 1.5 diesel) as ‘pretty basic.’ You have sensors which talk to receivers concealed in the wheel arch liners These can sometimes go wrong, which could cause the problems you’re experiencing. Power supply, or lack of it, which could be down to something as basic as a poor earth might explain the intermittent nature of your issue. My spanner wielding informant said that plugging the car in to the appropriate diagnostic kit should reveal problems of this sort with specific fault codes. I hope you don’t think I’m being vague.

Lastly, and here I hope you don’t think I’m insulting your intelligence, but are all of your tyres puffed up to the approved inflation pressures? One over or under inflated tyre might be the cause of your unwanted light show.

Best wishes


Hi Doc 

Thanks for your reply. 

After the sensors were replaced, the car was connected to diagnostic equipment at the Ford garage several times, but it never showed a fault code and they said that they even got somebody at Ford HQ to check it out without any Joy. 

From what I read on the internet, the Focus has a TPMS system where the sensor in the tyre communicates directly to the car’s ECU, but this is all above my head.

I spoke to a local independent garage a while back and they said it was probably the central control unit that was faulty. I asked how much to replace it, and all they said was get rid of the car. Replacing four sensors cost me £230, so I will probably not spend any more money trying to get it sorted and just put up with it.

I keep the pressures at 31psi. I hope my query didn’t give you sleepless nights thinking about it, but thanks for taking the time to make some enquiries for me. 

All the best


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