Parking sensors disable themselves

[twabrigs]

I have an occasional problem with the parking sensors.

I always leave them switched on and 90% of the time they work, madly beeping as I shunt forward and back squeezing into whatever space I need to. But sometimes they just simply make no sound, until I use the switch in the centre console to turn them back on...and I have NOT switched them beforehand. Just today they worked fine when coming out of a space outside a shop, then when I parked at home 4 minutes away they were 'off' again. Short journey, no iStop, no ignition off or anything.

It's irritating because you kind of get used to relying on them and you don't know if silence means you have loads of room or have they disabled themselves again. I've also never understood what the light in the switch means - when illuminated does that mean the parking sensors are operating or not operating? It's usually not illuminated for me and as I say that's them working almost all the time.

I somehow get the feeling it's not an intermittent electrical switch fault, if seems more like there is some deliberate logic that chooses when to turn them off.

Any ideas?

[Deeps]

If it's any consolation at all - I'm having the same kind of difficulty. I don't think it's a technical problem, more one of understanding the written instructions in the handbook. I've read the relevant section a few times and am still not 100% clear on what it's describing so perhaps it's a Japanese > English translation thing.

Now what really annoys me, however, is the extremely low volume of the reversing sensors. In my previous vehicle (VW Touran) the tone was emitted somewhere at the front of the vehicle so the volume was essentially the same from either front or rear sensors. This morning, however, the service technician at my Mazda dealer informs me that the emitter for the rear sensors was located under the cladding at the rear of the vehicle with the volume being non adjustable. In the comfort of my underground garage I can, by really concentrating, make out the tone from the rear sensors but out in the real world traffic - not a chance. OK, my hearing is not as it once was but you'd think that Mazda would at least provide audible volume at the same level for all sensors - front or back - irrespective of where the actual sensors are located.

[xtrailman]

The parking sensors only work at low speed, under 19mph I think it says in the manual.

The front sensors will not work at all unless you push the parking sensor button first, OR you have just selected reverse then moved forward under 19mph.

Same as the OP when I first bought the car I assumed the front sensors would always be active, but no, apparently most sensor systems work like this.
I don't know for sure as this is my first car fitted with them.

[twabrigs]

Ah - interesting. I knew about the under 19mph (or at least I knew they'd only work a very low speeds) but the reverse first thing could be why they often work but not always. I'll have to test it out.

I suppose it makes sense, otherwise they'd ping every time you came up behind a car at the traffic lights.

[Caldean]

My Jag does the same. Off unless reverse is selected first, moving forward first I have to manually switch them on. Mostly wheeling  straight into the garage I have to turn them on, although the benefit is limited. Best idea is my tennis ball hanging from the garage ceiling. When it hits the windscreen I know I'm 18 inches from the end wall. Works every time and doesn't go faulty !

[xtrailman]

I drive my car into the garage onto a piece of wood screwed to the floor, at that position I have plenty of space to use the sink unit, or load the boot.
Simple is always best.

[rmvf]

I know one thing I wouldn't be without them,  my wife lost concentration reversing out of a parking spot today and if we  didn't have I'm sure it would have been a bump