Tyre Pressure Monitoring System

**hooba** · 26-05-2010, 07:35 PM

Originally Posted by Maverick

Volkswagen Tyre Pressure Monitoring System (TPMS)

Fitting a direct Tyre Pressure Management System (TPMS)

Many thanks for posting this, invaluable information and good read.

**GTI6** · 17-10-2010, 10:50 PM

I was driving down to from Newcastle to Sydney today when the low tyre indicator turned on and the MFD read "please check tyres". So I got out of the car and walked around to find all tyres were ok. But when I started up and drove very slowly, the left side of the car developed a scratchy screeching noise every time the wheel turned to a particular spot. So I got out at a service station. All tyres were at 38psi.

I called Volkswagen Assist and they advised me that a stone chip may have got into the brakes and told me to go forward fast and suddenly brake, then go backwards and suddenly brake. After that, the screeching noise stopped and I was able to reset the low tyre pressure indicator. I was able to drive back to Sydney. Along the way, I stopped at service stations to check the tyres, but sometimes they were reading high, sometimes low, so I dont know what to trust.

Do you guys reckon its safe to continue driving it or should I go to a VW dealer and get it check out?

**Corey_R** · 18-10-2010, 07:51 AM

The low tyre indicator is run from the ABS sensors. Basically what happens is if a wheel starts consistently rotating at a different revolution to the rest, it determines that it is going flat. The fact that you were hearing a scratchy screeching noise, and then performed the braking maneuver and couldn't hear it again, I'd say it was ok.

About the only thing that I would have done before calling VW Assist is to thoroughly inspect the tread surface of each tyre to make sure there was no nail/screw/bolt in them which was causing that noise.

As for tyre pressures varying, that is normal. Although it could have been occuring for two reasons:
1) Tyre pressures increase and decrease as tyre temperatures change. Just watch a few NASCAR races to understand the importance and effects of that

2) Tyre pressure guages at servo stations are not the most accurate of devices, and they vary somewhat too!

**XTC838** · 07-06-2012, 10:02 AM

Does anyone know how much drop in pressure is required to trigger the TPMS?

I checked my tyre pressures over the weekend and they had dropped to 34psi from 38psi, but there was no TPMS alarm.

Just wondering if mine is faulty?

**T Go** · 07-06-2012, 10:39 AM

I've only ever had mine go off once and thats when I had a puncture, so it must be a pretty severe drop to get it to go off.

**Diesel_vert** · 07-06-2012, 11:14 AM

Originally Posted by XTC838

Does anyone know how much drop in pressure is required to trigger the TPMS?

The warning light is supposed to trigger once the inflation pressure falls by approximately 0.4 bar or 6 psi.

This is partly to account for everyday variations in pressure due to temperature (gases expand when heated and contract when cooled). Otherwise, the warning light would go off all the time.

**XTC838** · 07-06-2012, 11:23 AM

Originally Posted by Diesel_vert

The warning light is supposed to trigger once the inflation pressure falls by approximately 0.4 bar or 6 psi.

This is partly to account for everyday variations in pressure due to temperature (gases expand when heated and contract when cooled). Otherwise, the warning light would go off all the time.

Ok, that explains why mine hasn't gone off as it's below the threshold.

Cheers guys!

**entice** · 07-06-2012, 05:25 PM

isnt it a comparison to other wheels on the same side of teh car???
is, if both tyres drop, then it will not register.

**Diesel_vert** · 07-06-2012, 06:08 PM

Originally Posted by entice

isnt it a comparison to other wheels on the same side of teh car???
is, if both tyres drop, then it will not register.

Yes, the first generation indirect TPMS could only reliably detect punctures (i.e. sudden or rapid loss of pressure).

A second generation indirect TPMS should be capable of detecting a gradual or natural loss of pressure (i.e. through diffusion).

**ralp2dam** · 07-06-2012, 06:14 PM

Originally Posted by Diesel_vert

Yes, the first generation indirect TPMS could only reliably detect punctures (i.e. sudden or rapid loss of pressure).

A second generation indirect TPMS should be capable of detecting a gradual or natural loss of pressure (i.e. through diffusion).

When is 1st and 2nd generation ie what years or models?