Run flat indicator keeps coming on

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Wij

New Member
Joined
Oct 18, 2023
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13
Location
Nottingham
Car
W204 C350 cdi
Hi, i had my wheel hubs replaced on my w204 facelift c350 today after i got the car back i keep getting the warning that tyre pressure is low & check tyre pressure then reset run flat indicator. Ive tried resetting a few times and each time it comes back on. I tried googling where the placement of the sensor for it is but i keep getting results talking about the abs sensor, is the abs sensor the same one also used for the run flat indicator sensor and if yes where is it located and would i need to buy new ones with my wheel hubs or can old ones be reused?

Thank you
 
There are two types of Tyre Pressure Monitoring Systems (TPMS).

The basic type simply uses the wheel speed sensors to determine if one wheel is turning at a different rare to the others, and will trigger the tyre pressure alert if it detects this. The wheel speed sensor is the same one that is used by the ABS and ESP systems.

The higher end TPMS uses tyre pressure sensors inside the tyre valves, that transmit the tyre pressure data to an ECU via radio. This system can display the actual pressure for each wheel.

It seems that your car has the basic TPMS that uses the wheel speed sensors. However, I doubt that there's an issue with the wheel speed sensor itself, because then you'd also get ABS and ESP error messages.
 
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Thank you, in that case ill double check for nails or anything on the tyre because i drove for a while and tyre pressure seemed to remain the same, didnt have a chance to check the pressure with a punping kit but the tyres didnt look like they lost any pressure
 
As you have had work done on the hubs, where the speed sensors are, double, triple and quadruple check that they're seated correctly in their hubs. Unless they are, you'll get errors like the one you're getting.
 
You need to check the pressures with a gauge unless it shows the pressures on the dash, I guess it’s just doing it’s job, if it’s the basic TPMS it will keep displaying until the tyres are similar pressures.
 
As above. Check that the tyres have the same pressures right and left.
 
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Thank you, in that case ill double check for nails or anything on the tyre because i drove for a while and tyre pressure seemed to remain the same, didnt have a chance to check the pressure with a punping kit but the tyres didnt look like they lost any pressure

If you have runflats then you may not visibly see any difference, that's the point of them.
 
If you do not have a 'radio' sensor inside each wheel you have a problem with the wheel speed sensors on your hubs. Easily checked with a basic scan tool that can read live data .

If the sensors see a discrepancy in wheel speed for a given time the car assumes a puncture on one of the wheels and gives a warning on the dashboard.
 
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Thank you everyone for the replies. Ive checkee toppes up the air now theyre all at 38 psi im going to give it a little bit of time and go check them again just incase its a slow puncture. My car has the basic TPMS system based on the replies. If pressure stays the same then i can assume its the sensors and take it to a garage to have them scan it. My car knowledge isnt the best but is the wheel speed sensor built in with the wheel hub? Or can i have the mechanic just replace the sensor on its own and not the whole wheel hub again.

Thank you
 
Hi, i had my wheel hubs replaced on my w204 facelift c350 today after i got the car back i keep getting the warning that tyre pressure is low & check tyre pressure then reset run flat indicator. Ive tried resetting a few times and each time it comes back on. I tried googling where the placement of the sensor for it is but i keep getting results talking about the abs sensor, is the abs sensor the same one also used for the run flat indicator sensor and if yes where is it located and would i need to buy new ones with my wheel hubs or can old ones be reused?

Thank you
As far as I can see, the Lowest Common Denominator here is you had no Run Flat Indications until after the Wheel Hubs were Replaced! :rolleyes:

Solution to the Equation, take it back to the Place that Replaced the Wheel Hubs and ask them Politely to check the Sensors are Installed Correctly!;)
 
The sensor is a separate item that's supposed to fit precisely in the hub. Even if it's only slightly adrift it will give odd messages. They are indeed available on their own and are easy to fit.

I've just seen the advice in the post above. It's good.
 
It's a bit long but skip to 7 mis 25 seconds to see a fella dressed as a childrens entertainer removing the wheel sensor, you will see how it is possible to cause damage at this point . 26:20 he is seen replacing it.

I did not watch to the end where a talking bear and a purple dinosaur show us how to check the tyre pressure.

 
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I still think that it's odd for a wheel speed sensor to fail and not have ABS/ESP warning on the dash.
 
When i went back to my car yesterday after 8 hours of just letting it sit with the air topped up the pressure on all tyres went down; by 6psi on 3 tyres and 4 psi on one of the tyre. So now i was thinking would the pretty drastic temperature changes be causing this since in the uk right it gets to between 2°C - 0°C and as i drive and the wheels heat up the pressure most likely increases by good amount im assuming. They only removed the front wheels since i only had the front wheel hubs done as they were warped but all pressures went and i tried having a look and couldnt see any nails in the tyres either. All 4 tyres are different so i think thats why one might have lost less pressure. If my assumptioms are incorrect in the slightest I would appreciate any feedback.

Thank you everyone for the replies
 
I havent checked what the pressure gets back up to after I have driven but mid drive the red message saying "tyre pressure check tyres" comes on so thats why im assuming the tyre pressure increases by a fair amount to trigger it again. Would i be correct in thinking this or should i still have the sensors looked at by a mechanic?
 
When i went back to my car yesterday after 8 hours of just letting it sit with the air topped up the pressure on all tyres went down; by 6psi on 3 tyres and 4 psi on one of the tyre.
6 psi seems a big drop to be caused by ambient temperature alone; when you topped the tyres up to 38psi were they cold or had you been driving on them beforehand?
 
Regardless, as long as all tyres decrease in pressure at a similar rate, TPMS won't issue an alert (because it is based on relative rotation speed, and not on actual pressure).
 
Additionally, my own experience with the ABS/ESP-based TPMS, is that it won't catch a small 5-6psi discrepancy in tyre pressure. On the two occasions that I had a puncture, by the time TPMS alerted me the tyre was already visibly very low on air.
 
When i went back to my car yesterday after 8 hours of just letting it sit with the air topped up the pressure on all tyres went down; by 6psi on 3 tyres and 4 psi on one of the tyre. So now i was thinking would the pretty drastic temperature changes be causing this since in the uk right it gets to between 2°C - 0°C and as i drive and the wheels heat up the pressure most likely increases by good amount im assuming. They only removed the front wheels since i only had the front wheel hubs done as they were warped but all pressures went and i tried having a look and couldnt see any nails in the tyres either. All 4 tyres are different so i think thats why one might have lost less pressure. If my assumptioms are incorrect in the slightest I would appreciate any feedback.

Thank you everyone for the replies
Confused of Lincolnshire here. The front hubs were warped? Or do you mean the front brake discs?
If the discs, then I do not think that changing them would involve disturbing the sensor, but I have been known to be wrong on very rare occasions.
If it was the hubs, that would be a first for me!
 
I havent checked what the pressure gets back up to after I have driven but mid drive the red message saying "tyre pressure check tyres" comes on so thats why im assuming the tyre pressure increases by a fair amount to trigger it again. Would i be correct in thinking this or should i still have the sensors looked at by a mechanic?
Tyres always warm up when driving, so any warning system will take this into account (or half the cars on the road would be flashing up warnings every day). You should definitely do as John N says above and take it back to the place that replaced the wheel hubs, explain that you are getting these warnings ever since they did the work, and ask them to check that the sensors are installed correctly.
 

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