Tyre pressure check light run flat indicator

Paiwand mustafa

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Hello friends my Car keep showing check tire pressure in last 6 months when all my tires are fine and new and all pressure same as each other and correct

MY car is Indirect TPMS works with your car’s Antilock Braking System’s (ABS) wheel speed sensors and There is not valve sensor inside tye wheel.


They been advising me to change both front tyres and i did change them but unfortunately after spending a lot of money for check and diagnose the car still keep showing tyres pressure check i diagnosed with the car scanner it shows (N30/4 ) do you guys think it might be abs control module? Thanks please advise me also i can send my unit many thanks
 
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Paiwand mustafa

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Yes i have reset it and its correct tyre as well but I still have the problem unfortunately
 
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Paiwand mustafa

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.... and you've definitely reset the system on the dash cluster after you've checked the tyre pressures?
Yes i did but unfortunately it still same
 
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brandwooddixon

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Perhaps there's a reluctor ring or ABS sensor issue. Not enough to trigger a fault on the sensor, but enough to put the speed signal out.
 

Botus

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Most ABS sensor derived (as you say indirect) tyre height indicator systems have a user instigatable calibration feature - every now and then you should inspect the tyres, inflate to standard settings, then run the calibration feature - and drive gently on a smooth flat road in STRAIGHT line for about 200 to 500 yards and its brain re-senses what normal looks like - when its determined the noise of each sensor seems valid and doing what it expects it will decide that's the new normal...

it helps when running with naff brands, miss-matched brands and a new tyre vs a worn tyre

if you buy a ford / pug (maybe others) where they may have fitted either type, the manu often forgets to remove the indirect calibration menus and people with real sensors get confused...

that last bit is NOT the same point as a Merc with real Highline TPMS where you can inflate the tyres and tell the car this pressure is the new reference point - which can be helpful if running funny wheels or winter tyres

FYI - tyre height sensing was to be banned in 2012 as its naff and too slow to the party - but VAG paid off a few EU crooks to claim its OK. Thus in 2016 they rewrote the law, bending to undue pressure from bent german manufactures

The really stupid element of real sensors, is (to fiddle the reading to make them appear more stable between min max ambient temps) they ALL have tyre temperature sensing alongside the pressure readings. So we could for FREE have 'cold tyre temp drive gently', and 'overheating caution - risk of blow out' alarms on the dash too

On the BMW's the bike's mostly have the display turn-onable

2023-11-29_113108.jpg
 
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DSK

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UncleBenz mentioned a very good point which I failed to acknowledge when o had my issue. Reset it, when the tyre is cold!

I had a similar issue on the cls219 recently. New tyres, all tyre pressures correct, no air leaks etc. the tyre pressure warning was just relentless. I tried resetting it several times but did so on the move or when parking up etc. Then it suddenly stopped happening as the car was due to go in for a service… typical. So perhaps i may have rest it one time in a manner that was correct.


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Botus

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this might be linked to indirect tyre height misreading - I've just been doing wheel bearings - on many Merc's the rotating element of the reluctor feeding wheel speed to the ABS wheel sensor - is the face of the bearing seal... Never looked before but you get a pattern build up on the seal face - of magnetised brake disc.

Lots of posts over the years saying to resolve ABS bugs check clean the ABS sensor / reluctor area - but you can't easily - its in a bucket and pulling a sensor out from behind - as I did earlier on the year is totally ineffective - its magnetic so you wipe and it just disperses and then rebuilds to exactly the same state with one revolution of the wheel

I thought the visible pattern on the seal was a design feature, and I had the wrong new plain seals - then thought I was going mad - you wipe the original seal to look and it wipes clear just like the new seal - but when you put the hub down the pattern comes back !

(radial marks are not real - its magnetised dirt)
Magnetic.jpg
 
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