Yes, it's that common electrical fault: the parking sensors. It's driving me insane, so I need some respite.

Basically, I had a sensor die on me lately. The car did have a sensor fault sound intermittently in the past, mainly in the winter, which I chalked off to it being down to mud and grit getting on the bumper and messing with the sensor's ability to work. But just after getting my latest MOT, I started getting the siren tone more often, until the sensors wouldn't work at all.

Now, I've done the trick of checking each sensor, as I've read off here in previous threads about the topic. My car has front and rear sensors, but the one that isn't clicking is the inner left rear sensor. I bought a replacement online from Ford Parts UK, and fitted it. The alarm still went off. Having tried the sensor I received in another socket with a working sensor, it does work, so I've not been given a dud replacement. However, now I'm stumped as to what to do. I used WD40 to clean out the socket and surrounding wires, which don't seem to show any hint of wear and tear, but the alarm still sounds.

Any ideas on what to try next? I'd rather not have to go to the local dealer given how expensive the repair usually is, and this isn't a feature that's critical enough to warrant that price tag. The previous owner clearly thought so; I just wish this was as easy as swapping the sensor out.

Thanks in advance.

What tone or tones do you get? Obviously with nothing to front or rear of vehicle.

I get a tone that goes up and down with three beeps at the end whenever the reverse gear or parking sensor button is engaged. The sensor button LED also flashes.

3 beeps is right hand inner, either front or rear depending on first sound.

Ah, my bad. It's actually two, so that would mean the inner left, no? I've uploaded a recording to my Dropbox.

https://dl.dropboxusercontent.com/u/18792399/20150723%20132204.m4a

2 is left inner,

Definitely the one I replaced. All the others you can feel working when engaged.

So now you will need a multimeter and check the wiring from sensor connector to parking aid module

Good point. I can't imagine it to be damaged, judging by the wire coating and the fact that no other sensor on the loom seems impacted, but I'll give it a shot.

Incidentally, where is the parking module? I read it was in the boot somewhere.

In boot, behind trim on right,

Check the multiplug behind bumper also before it goes in to boot., theres also splices in loom that all sensors split from for live , ground sensing.

Awesome. Will need to get a hold of a multimeter first. Much appreciated.

No problem, if the wiring is ok, then only thing left is module, but im betting its a corroded/broken wire.

Would that be easy enough to fix myself?

Depends how handy you are with wire crimp connectors or soldering iron. If you can locate where the issue is and dont want to do it, get someone else to do it , needs to be a good fix .

I know this is an old thread but I’ve just got this problem. Is there a list of what beeps mean what sensor? 

Thanks 

Recorded the sound if anyone knows what 8 beeps means. 

https://www.dropbox.com/s/fv80ipy2b51lyfp/Fiesta 2011 Beep.m4a?dl=0

Could be anything as they are not ford sensors.

oh! The person I bought the car from said that they were on the car when she bought it new from the dealer. It has a parking assist button that also flashes. Four front, four rear. I’ll take it to my local ford dealer and see what they say. Thanks 

I stand corrected,  didn't realise you had front and rear, the info I have says only 7 bleeps max but that for ford rear sensors only. Will go see if I can find out for front and rear. 

Right, is the sound and beeps coming from the front or rear? 

4 hours ago, iantt said:

Right, is the sound and beeps coming from the front or rear? 

Apologies for not being clearer in my first post.  Thanks for getting back to me. 
It sounds like it’s coming from the front center dash air vent area. 

Ok, if the sound is from the front  and 8 beeps , that indicates rear speaker failure.

3 second prelude tone + 8 beep tone from front speaker

Rear speaker failure

9 hours ago, iantt said:

Ok, if the sound is from the front  and 8 beeps , that indicates rear speaker failure.

3 second prelude tone + 8 beep tone from front speaker

Rear speaker failure

Thanks for getting back to me again. I checked all the speakers in the car using the balance and fade settings. All appear to be working. Is there any other way of checking?

is the speaker for the parking assist separate from the radio speakers? If so, where is it located?

Found it!