tpms

[Paulmar]

have had no problem with the tpms for long time then last week had flat but didn't show on dash did a scan of car and report says that there's no tpms on the vehicle what possible reason could cause this and is it an easy fix

 

[Blobcat]

Does it have pressure sensors? A lot of the systems work on the difference in rolling speed of a tyre with lower pressure - the car calculates it from the ABS wheel speed sensors.

 

[Paulmar]

Does it have pressure sensors? A lot of the systems work on the difference in rolling speed of a tyre with lower pressure - the car calculates it from the ABS wheel speed sensors.

couldn't tell you if it did have them all I know was working last week then stoped have had tyres replaced and still worked it don't show any only scanner

 

[mioba]

Mercs have 2 different systems for pressure monitoring.

TPMS - This tells the pressure of each tyre on the dash. You usually have bolts on the valves to easily id this system.

Run Flat - as above measures the rolling speed of each wheel to id a flat. You need to reset this after correcting tyre pressure

so what systen have you got

 

[onefortheroad]

Its a 2012 so probably normal rubber valves and abs system.

 

[Paulmar]

Its a 2012 so probably normal rubber valves and abs system.

yes valves are rubber

 

[EmilysDad]

Mercs have 2 different systems for pressure monitoring.

TPMS - This tells the pressure of each tyre on the dash. You usually have bolts on the valves to easily id this system.

Run Flat - as above measures the rolling speed of each wheel to id a flat. You need to reset this after correcting tyre pressure

so what systen have you got

Not just Mercs ..... and technically the other system is a tyre deflation monitoring system

 

[Botus]

it would help if you explained what you thought you had and how your thought it was working the week before...

did you ever have the pressure read outs for each wheel in the cluster?
what tool did you scan the car with to find out it doesn't have TPMS? (TPMS is a much higher level of diagnostics and few tools support it).

In 2012 the law said you have to tell the driver if you have a puncture.... many do it the cheap way using the ABS sensors - they should be reset after changing tyres to accommodate the slight differences in rolling circumference between brands and between old & new tyres....

 

[Paulmar]

no never had individual tyre pressures showing on car it just says reset run flat and active and when tyre was low low it used to bring up warning on dash then pump it up and reset it I used a launch x431 pro also had a tyre place use there scanner

 

[EmilysDad]

no never had individual tyre pressures showing on car it just says reset run flat and active and when tyre was low low it used to bring up warning on dash then pump it up and reset it I used a launch x431 pro also had a tyre place use there scanner

you don't need a scanner to tell your car that all the tyre pressures are correct .... it's done via the dash cluster after you've inflated to the correct pressures

Though you can reset it at what ever pressures you want ... you can have all 4 different if you want

 

[Paulmar]

you don't need a scanner to tell your car that all the tyre pressures are correct .... it's done via the dash cluster after you've inflated to the correct pressures

Though you can reset it at what ever pressures you want ... you can have all 4 different if you want

I know u dint need a scanner to tell me the tyre want down and didn't come up on dash that's why yi used a scanner to check for faults and then found out that it says not on vehicle where as before it was there working fine

 

[mioba]

OP, you clearly have run flat as you describe.

Its not showing in the screen - then use the arrow/menu buttons on the steering to get it showing in the display.

It cant just disappear

 

[Botus]

no never had individual tyre pressures showing on car it just says reset run flat and active and when tyre was low low it used to bring up warning on dash then pump it up and reset it I used a launch x431 pro also had a tyre place use there scanner

so you have ABS driven system? - it works as mentioned in the second post - on the difference in rolling speed of a tyre with lower pressure

where you say it used to tell you to pump up a tyre - these are quite insensitive and usually never tell anyone anything.... so getting a regular message suggest something was wrong - sounds like you had a slow puncture before changing?

If you now have issues, did you really change wheels and or tyres sizes when you JUST changed the "tyres" ? As it works from the distance one tyres is travelling vs what's the car thinks that wheel location should be doing you can't just change stuff to different sized wheels / tyres.

it tends to have 10% slop built in (for wear / small tyre pressure differences) go to 12% difference and the car won't cope - if you have the original wheels and std tyres sizes all round and the pressures are correct - check the handbook for the manual reset / calibration procedure (often drive slow on smooth road, no corners press reset - drive 1/2 mile all done)

if that's doesn't work check ABS sensor operation

 

[Paulmar]

so you have ABS driven system? - it works as mentioned in the second post - on the difference in rolling speed of a tyre with lower pressure

where you say it used to tell you to pump up a tyre - these are quite insensitive and usually never tell anyone anything.... so getting a regular message suggest something was wrong - sounds like you had a slow puncture before changing?

If you now have issues, did you really change wheels and or tyres sizes when you JUST changed the "tyres" ? As it works from the distance one tyres is travelling vs what's the car thinks that wheel location should be doing you can't just change stuff to different sized wheels / tyres.

it tends to have 10% slop built in (for wear / small tyre pressure differences) go to 12% difference and the car won't cope - if you have the original wheels and std tyres sizes all round and the pressures are correct - check the handbook for the manual reset / calibration procedure (often drive slow on smooth road, no corners press reset - drive 1/2 mile all done)

if that's doesn't work check ABS sensor operation

thanks ill give that a go

 

[jimbg]

Mercs have 2 different systems for pressure monitoring.

TPMS - This tells the pressure of each tyre on the dash. You usually have bolts on the valves to easily id this system.

Run Flat - as above measures the rolling speed of each wheel to id a flat. You need to reset this after correcting tyre pressure

so what systen have you got

On later cars the run flats also have TPMS and pressure readout in the car and on the app.

 

[Botus]

On later cars the run flats also have TPMS and pressure readout in the car and on the app.

the law was tweaked in 2016 mandating there MUST be a system to inform the driver

the run flat terminology people are using here is confusing me.... run flat tyres are a hideous disaster than makes cars unsafe to drive, but does offer more resistance to unwanted deflation

the rest of the car industry moved to more obvious description of the two systems

direct TPMS (with real BT sensors)
indirect TPMS (with ABS sensor info and some maths)

BOTH are tyre pressure monitoring systems - one is a posh one that can give tyre temp and pressures, the other is just maths

 

[EmilysDad]

The other system is actually a tyre deflation monitoring system

 

[Bay Leaf]

I'm totally lost here. I have a 2013 SL with a pump and a canister of sealant. So do I have run flats or normal tyres. I've tried to decipher the tyre markings on the wall to no avail.

 

[Botus]

you can fits nasty tyres with stiff sidewalls "usually called run flats" they are hideous, dangerous rubbish, that ruin ride comfort and can make the car extremely lively to various camber changes on the road. They are also heavy, so unsprung weight goes up and handling goes down. Plus they also cost lots. The idea is even with a puncture the tyre retains its shape and you can carry on driving for up to 100 miles.

I was once on a smooth bit of road in the damp in my 335d and I could only just keep the car in the lane, it was trying to do a U urn on me. I stopped dead sure I had a puncture... there was nothing wrong. I was regaling the story to a mate at work and he had had the exactly issue the same weekend with his 5 series, he had stopped to check his wheels weren't physically falling off the car.

Then you can have real tyres that get punctures but you might live long enough to actually get a puncture

These days Pirelli have "normalish tyres" with a layer of yellow gunge we weeps out any hole pretty much giving the benefit on run flats but with the cost handling and comfort of a real tyre.

.... swings and roundabouts

Having a puncture kit in the boot doesn't help you understand what's fitted on the car now. But it would suggest Merc felt the need to use normal tyres and try to help should you succumb to the rare event of a puncture... Which sadly in the UK usually translates in to one every 3 months as bob the builder scatters nails, screws and other debris out the back of his van as he practices rally driving techniques, trying to get "proper air", as he tackles speed bumps on residential roads at 60mph

It has always perplexed me how the local councillors believe unmaintained builders vans 2 foot off the ground at 60 mph, can stop more quickly than I think they would if we had smooth flat roads?