Technical Reversing sensor failure

[Daveof49]

The Reversing sensors on my 56 plate Croma stopped working when we had the really bad frost and low temperatures in December 2010.
Keep getting the message of 'Parking assistance not available'. Has anybody else experienced this?
Its going into the garage (non Fiat) in two days time for this to be looked at but I have a feeling they will not cure it!
Any help will be much appreciated. Thanks.

 

[DoIDon'tI]

Yes, there is another thread on the Croma forum about it. Not uncommon, the garage will easily cure it but you might be unpleasantly surprised by the parts prices. Have a search for the other thread (from memory I believe it's called 'Faulty parking sensors), if you decide to do it yourself then BMW E39 and E60 PDC sensors with a right-angle connector and three pins will fit and are cheaper. I've changed all four on mine, there aren't any original Fiat ones fitted any more. It would appear it's a poor quality part which is also prone to failure when fitted to BMWs.

Just one point - it's not uncommon for these sensors to fail but give no warning. Unless it's the one on the end that fails, generally the overlap from the other sensors will cover the 'dead' area so the problem is masked until another sensor fails, then you find out you've actually got two dead sensors. I found this out when testing my sensors after replacing the one which was giving the warning - one of the supposedly serviceable ones was not giving any signal.

 

[Daveof49]

Hi DoIDon'tI

The garage could not get the reversing sensors to work. They said their fault reader could not read Fiats!!??. Mind you this is only to be expected these days. They say that the fault could be with the sensors or the control box/computer. You say you tested your sensors and found two defective. How did you carry out the tests where did you get the replacements and how much did they cost?

 

[DoIDon'tI]

Both sets came from ebay, the first pair cost me £45 and the second pair £25 (I was lucky, also watched several over a period of time). BMW part numbers include 6989068,6989070, 0306567 and 6938738 amongst others.

Test procedure is;

Replace one sensor at a time, start the car and put it into reverse and see if the warning triangle on the dash goes out. Repeat until you find the dodgy sensor. The other thread I mentioned gives advice on removing the sensors. Top tip - don't press the sensor too hard when trying to get it out or you run the risk of breaking its mounting bracket off the bumper. Don't ask me how I know that

To test the others;

Get an assistant to sit in the car with the engine running, windows down (so you can hear the beeper) and reverse engaged. Get a broom or similar and stand at the side of the car at the rear, then put the broom head a few feet away from each of the rear sensors in turn and check that they all activate the beeper. You could do it from the rear of the car but there's a chance you might get an overlap - if you bring the broom head down from above each sensor you should just activate that one.

Go to the other side and repeat for the one(s) you couldn't reach.

Oh, and cross your fingers that the faulty one is one you can get to without removing the rear bumper - it's held on by 31 fasteners on my car (25 if you haven't got mudflaps). If you have a towbar then you can only realistically get to one sensor - call it natural justice for clogging up the roads on bank holidays

Hope this helps.

As a footnote, the garage would need the Fiat 'examiner' computer system to interrogate the car fully as parking help faults don't show up using an ordinary code reader.

And just to make things more interesting, you can only test the sensors when they're working; rather unhelpfully, the first thing the car does when it detects a fault is to shut the system down so you can't test which one has gone wrong. I wouldn't recommend doing resistance tests etc as the sensors are quite delicate and complicated bits of kit. So, the only way is good old fashioned 'slaving in' of known serviceable sensors - unless you take your car to a main dealer?

 

[abininie]

Me too
Told that salt or water got into sensor now working intermittently

Amanda

 

[Daveof49]

Took car back to garage it was brought from who checked it on their reader. Turned out it was sensor no.1 that was faulty. Apparently £60+ to buy new one from fiat dealer. Luckily I had a one year warranty thrown in when I bought the car so it hasnt cost me anything. I have been told that really cold weather can cause these sensors to pack up.

 

[Doofer]

Does anyone know if these are designed to be fail-safe? i.e. is it possible for them to fail in such a way that the system doesn't know they've failed, but you never get the beeping?

This is the first car I've had with them and I've soon got used to having them, especially for parking up to a wall or another car.

 

[s130]

If you have a towbar then you can only realistically get to one sensor - call it natural justice for clogging up the roads on bank holidays

But when my rear sensors fail my bumper and towbar will be unaffected and I'll only know I got too close when I'm towing the front of your car down the road when I move off!

 

[Doofer]

 

[s130]

Close but......you post a plastic/wooden wobbly box (as truckers call them). Try a steel shelled aluminium skinned, aircraft engineer designed rigid brick on wheels. Not an Airstream but much better.

Yes like the poor old HMS Sheffield destroyer an Exocet missile might just achieve what you want

Heeee heeee are we Croma owners having fun?

Anyway, back to reversing sensors

If you get FiatECUScan or other similar diagnostic kit you can test the sensors and turn them on/off. There is a trailer (sorry CARAVAN) attached input that if using a pucker manaufacturers wiring allows automatic enabling/disabling of the sensors.

 

[Doofer]

Mine are working fine, but I just noticed that one has been pushed in. I pressed it to see if it was loose, and managed to push it in further.

It's obviously come unclipped somehow. How do I get to the back of it (inside the bumper) to fix it?

 

[s130]

You can get a little access from underneath the bumper. If you have a tow bar fitted then life becomes a liitle more tricky.

Odly I tested mine today and it looks like I have one that is 'off-line'. Center N/S.

When I get a chance I'll hit the system with FiatECUScan to see if anything is logged as broken or not working correctly.

Just had my rear bumper resprayed after a minor reversing incident in cold weather where the sensors (actually outside N/S) did not pick up a 1 inch wide steel pole....ouch. Could mean that removing sensor without damaging the new paintwork around the holes could be very difficult.