Them pesky parking sensor thingys..

Now I read somewhere on here that you get your trusted partner to sit in the car whilst engaging reverse and standing on the brake pedal. Fortunately I have such a trusted partner so got her to do that.

I then went round the back and listened to each sensor. On the rear, all but one were clicking and on the front they all were. I then re-read the article here and it says that if they were clicking they are faulty! Is that right & I have need to replace 7/8 of them or is it just the silent one that's knackered?

Second question is that I'm guessing its a bumper off jobbie? No-way can I get my hands in around the back of the sensor...

I thought it was if they weren't clicking it meant they are faulty? I am sure someone more learned will come along and give more meaningful advice soon

Seems that the one 'not clicking' is the faulty one
One fo a few threads on the subject here

To bring them all up, stick +faulty +parking +sensor in the search box  ON THE WAY: BMW F21 M140i
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Beancounter_74 wrote:

Seems that the one 'not clicking' is the faulty one
One fo a few threads on the subject here

To bring them all up, stick +faulty +parking +sensor in the search box

Aha - that is how to use the search better

This for the bumper removal instuctions...

http://www.rrsport.co.uk/gallery/albums/us...0Cover.pdf

Now to find the sensors at a good price - anyone?

The clicking sound would be the "noise" the sensors send forward and listen to the echo to gauge distance, a bit like bats do

Not sure about rear sensors, but for the front ones, the bumper has to come off, just done two of mine this week end. Pretty easy to be fair, looks harder than it actually is.

The workshop instructions suggest you should disconnect the washer bottle pipe to the headlamp washer, but I found I didn't need to do this. Also, before you start pulling the bumper off, undo the two connectors on the driver's side. They're more or less under the headlamp and are the only two bundles of wires going to the bumper.

No need to raise the car either as long as it's not in access height you should be ok as it is, or disconnect the battery for that matter.

I'd recommend a wide piece of cardboard on the floor in front of the car to protect the bumper as you lower it on the floor and an assistant is recommended but not 100% necessary if you're careful.

Removing the sensors is pretty easy if you lay the bumper on its "front", there are two clips either side of the sensor that you need to prise apart with a small screwdriver (or two) and pull the sensor, pushing it from the other side helps.

Once you have pushed the sensors back in and connected them up, loosly fit the bumper back on, reconnect the two plugs (wires) and test it's all working before refitting everything. And no, letting the sensors "hang" to test before fitting in the bumper didn't work for me  

"Roads ? Where we're going there are no roads." Back to the future.

mrfrog wrote:

The clicking sound would be the "noise" the sensors send forward and listen to the echo to gauge distance, a bit like bats do

this is a joke right mr froggy?  ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

rrsboy wrote:

mrfrog wrote:

The clicking sound would be the "noise" the sensors send forward and listen to the echo to gauge distance, a bit like bats do

this is a joke right mr froggy?

Unless I am mistaken, that's how the sensors work, they send an ultrasonic wave, wait for the echo back from obstacle and determine distance from obstacle based on time/distance (sound travels at 330m/s). If no response, obstacle is too far to be a concern.

How else would they work ? Reaching little fingers out to feel for obstacles in the dark ?2 

"Roads ? Where we're going there are no roads." Back to the future.

ultrasonic as in inaudible to human ears? ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

RRSBoy, a little light reading for you...

http://en.m.wikipedia.org/wiki/Parking_sensors#section_1

rrsboy wrote:

ultrasonic as in inaudible to human ears?

Not sure what the actual frequency is, but a keen ear can pick up clicking from bats so why not from PDC sensors ? What else would the noise be ? 

"Roads ? Where we're going there are no roads." Back to the future.

beat to my edit - the 2nd system is electromagnetic - used to have it on a Lotus, it was actually pinched off a Subaru.. think strip of metal foil on the inside of the fibre glass shell  ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

simon1233 wrote:

RRSBoy, a little light reading for you...

http://en.m.wikipedia.org/wiki/Parking_sensors#section_1

a little for you too [url]http://en.wikipedia.org/wiki/Ultrasound_(disambiguation)[/url]

 ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

mrfrog wrote:

rrsboy wrote:

ultrasonic as in inaudible to human ears?

Not sure what the actual frequency is, but a keen ear can pick up clicking from bats so why not from PDC sensors ? What else would the noise be ?

you can't hear the ecolocation sounds that bats make without specialist equipment, because they are ultrasonic - you can on the other hand hear the sounds they use for communication (and for argument's sake perhaps the occasional secondary sound caused by an ultrasonic reflective distortion)  ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!

Ok, so what's the clicking noise from the sensors ?

Workshops manual states they are ultrasonic

"The system comprises 4 ultrasonic sensors in the rear bumper, 4 ultrasonic sensors in the front bumper (if fitted), a control module, a fascia mounted control switch, a rear sounder unit and a front sounder unit (integral with instrument cluster).
The system operates using ultrasonic signals which are transmitted by the sensors. The reflected echo from this output is received by the sensors and used by the parking aid module to calculate the distance from an object."

"Each sensor comprises a plastic housing which contains a piezoelectric disc. The disc resonates at a frequency of 38.4 kHz, producing an ultrasonic signal output. The disc also receives the reflected echo signal."

Wikipedia: http://en.wikipedia.org/wiki/Parking_sensors
"Although the sensors are ultrasonic and the majority of their output is beyond the range of human hearing, it is possible to detect a completely failed unit by putting the vehicle into reverse gear (with the ignition on but, for safety, without starting the engine) and listening closely to each of them. A working sensor makes a rapid clicking sound; a sensor that does not click, or is noticeably quieter than the others, is likely to be the cause of a malfunctioning PDC system."

Would this suggest a minority of their output is audible ? 

"Roads ? Where we're going there are no roads." Back to the future.

38.4 kHz is about twice the limit of human hearing

from Bobby, an easier way to diagnose a fault:

"The parking aid module has a diagnostic connection via the medium speed CAN to enable faults to be retrieved using a Land Rover approved diagnostic system. Additionally, an on-board diagnostic routine within the parking aid module constantly monitors the system and alerts the driver to a system fault by emitting a tone from the front or rear sounder, depending on the fault.

If a parking aid system fault has occurred, the parking aid module will relay the occurrence of the fault to the driver in the following ways:

*The status LED will flash at a frequency of 2Hz if the system is active and fault is detected in the sensors, sounders, related wiring or the module.

*The front sounder will emit an error tone for 3 seconds at a frequency of 1500Hz if a fault is detected with the front sensors or the rear sounder develops a fault.

*The rear sounder will emit an error tone for 3 seconds at a frequency of 1500Hz if a fault is detected with the rear sensors, the switch, the LED in the switch or if there is a CAN bus error." ============
2010 TDV8 HSE - ooo laa laaaaaaaaa
2007 TDV8 HSE - superb car and very reliable
============
2012 - dearly departed, sadly missed.. to return in late 2013 with a new TDV8!