TPMS issue

[milleplod]

I checked the pressure on all my tyres today - on first getting my '09 Exclusive, I'd get a ROS warning for low pressure once every 3 weeks or so - I've not had the warning for ages, hence checking pressures today. Both rears were down to 32psi, but no warnings given! So....am I looking at a 'coincidental' double failure? Shouldn't the system tell me if a sensor is down....ie 'oh my god there's no info coming through, abandon ship' sort of thing on the dash?!

Pete

[GiveMeABreak]

Should be about 2.4 Bar all round and 2.8 Bar at the rear if loaded, which is 34 / 40 respectively. So not a great difference there. Normally 2 warnings - one deflated then punctured. If you press the CHECK function on the dash, do they all come up as OK? I think if it were to fall much below 32 you would get the warning and yes, if they were not working they would tell you Pete.

[milleplod]

Should be about 2.4 Bar all round and 2.8 Bar at the rear if loaded, which is 34 / 40 respectively. So not a great difference there. Normally 2 warnings - one deflated then punctured. If you press the CHECK function on the dash, do they all come up as OK? I think if it were to fall much below 32 you would get the warning and yes, if they were not working they would tell you Pete.

Hi Marc.

I run them at 34/35 all round as the car's very rarely loaded. Perhaps they'd not dropped quite far enough to trigger a warning then. And....er....for the very first time in my ownership, I've pressed the 'check' button and got 4 'greens' and told I need a service in 14k miles. Perhaps I should've read the handbook properly.....

Many thanks!

Pete

[GiveMeABreak]

That's fine Pete - that indicates the system is working - if it wasn't you'd be right and there would be warnings about which sensor wasn't being monitored. The Check button is useful, as it also recalls any errors on the system (except when they are temporary and the ECU clears them itself), especially when you need to show the garage any messages the system has been flagging up.

[DickieG]

The trigger point for the sensors to alert you about a loss of pressure is dependant upon how they were set up, you can narrow/lower the trigger point by raising the "set" pressure to a higher figure than the car usually runs at. You need Diagbox and an "exciter" to do this but the procedure for installing pressure sensors involves raising the pressure of all tyres to (IIRC) 3.6 bar then lowering the pressures to whatever the standard pressure is and using the exciter/Diagbox etc. So for instance if you set it to say 2.5 rather than 2.3 on the relevant wheel the sensor will go off at a lower differential point.

[GiveMeABreak]

These newer systems on the X7 seem to like to be programmed as a set - I had an issue with the front right sensor always telling me there was a puncture - and there wasn't - I had tried to reset the damned thing by lowering the pressure right down then up and back to normal - but that just upset it completely. Taking it to the dealer I was told they have a certain tolerance level - but when they reset the specific sensor, I got 20 yards off the forecourt and back on came the warning again. This time when the technician looked at it the front left one was playing up! He took it back in and about 40 minutes later he told me he had to programme them all again as a set and that should resolve the problem - sure enough they have all been behaving and all the subsequent warning were genuine ones.

These were all new TPMS sensors - as I had them all replaced the year before under warranty with the new replacement types after one completely blew out on the carriageway like a bullet leaving a whopping great hole! Had them under health & safety - not just me but from the public perspective, because this could of killed a small child or put a hole in somebody's leg if it had happened in a crowded street. I told them I wanted the lot replaced as I was not prepared for this to happen again - they were all on the way out and were corroding terribly, so just as well.

Whilst on the subject, I would also advise anyone against using 'metal' valve caps. They started reacting with my valves, as I found out when the tyre warning went off recently - went to check the pressure with the gauge and couldn't unscrew the bu**er. Cue a pair of mole grips and sharp cutter to get the cap off! It disintegrated into pieces. Told Halfrauds they should remove them from sale and bought a set of plastic ones - lesson learnt.