500 500 1.3 brake/abs pump continually running

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500 500 1.3 brake/abs pump continually running

BigT100

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Hi guys, thanks for letting me join. I bought a 2008 Fiat 500 1242cc for my daughter which has run great for nearly a year. Then a couple of months ago, out of the blue when sitting parked outside the house the brake control pump started making a noise. Even when the fuses are removed it keeps going. It stops when I disconnect the battery. The brakes work ok although the EBS light is on of course. I’m at a loss as to why it would run with no fuse and no engine running. I don’t want to replace it before understanding what’s wrong in case it’s electrical. Any help would be greatly appreciated. The abs light was on previously but brakes were renewed.
 
I wouldnt normally say this but given its the ABS take it to the dealer for diagnosis or a dedicated brake specialist, be prepared that it could be more costly than thought like the wheel cylinders and calipers replaced(and the rest) have you looked for an leaks
 
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Hi and welcome to the forum.

You've had a spot of bad luck. This is most unusual; the ABS on the 500 is normally trouble free, so there isn't a great deal of collective knowledge on the forum about this.

I'd start by interrogating the car with a dedicated Fiat-specific scan tool to see what fault codes are stored.

IIRC the ABS pump is supposed to cycle each time the car is switched on; possibly whatever control mechanism is used to manage this isn't turning off correctly. Stuck relay, perhaps?

New ABS parts are prohibitively expensive, but used ones from the breakers are reasonably priced (there's not much market for them as they fail so rarely); the difficulty you face is probably going to be diagnosis and reprogramming. If it is a relay, and you can identify it, and you can by some means open the case of whatever module it's in, and you can find an equivalent relay (hint: try Farnell or RS components; failing that, swap the relay with one from a scrapped module), and you have decent soldering skills, then just maybe you could fix this quite cheaply without needing to reprogram anything.

If you haven't already got it, investing in a licenced copy of MES and the appropriate cables is probably the next thing to do. It'll likely cost you less than a main dealer diagnostic check, and you're almost certain to need it if you're going to replace any of the electrical/electronic parts. I'd be reluctant to go anywhere near a main dealer; the repair cost could easily exceed the value of the car. Most non-fiat general purpose garages won't have the necessary diagnostics, but an ABS specialist should.

And please come back and let us know what happens; we've very little information about these modules and your experience could help others in the future.
 
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Thanks for your advice. I’ll have a look at getting the diagnostics done and take it from there. Typical, my first main problem is an unusual one!

Cheers
 
As jrkitching has said, the ABS system is generally problem free, so if you need a replacement a used pump might be very reasonably priced.

Obviously the question of why the pump still runs with the fuse removed is that the fuse you’ve removed is not the right one.

Fiat are known for having different fuses in the slots for what you’d expect or what’s labelled so you would need to try other fuses to find out which one is the right fuse that’s powering the unit.
Though even then the question is just removing the fuse is not going to achieve a lot and would make the car an MOT failure and therefore would potentially invalidate the insurance if for example there was a serious accident and the car was inspected as a result and they found the fuse for the ABS missing
 
just removing the fuse is not going to achieve a lot

It'll stop the pump running, which just might prevent it from burning out and making the repair more costly

and would make the car an MOT failure

With a serious ABS fault, it already is. The brakes (though not the ABS) will work normally, so some might say it was reasonable to drive it to a place of repair. Pulling the fuse might reduce the risk of an uncommanded malfunction whilst doing so.

For similar reasons, I'd consider pulling the ePAS fuse if I had to drive a car with an intermittent power steering fault to a place of repair.
 
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and they found the fuse for the ABS missing

I didn't say this, but if you replaced the fuse with one that had already blown?

This reminds me of a story from the days when the Red Arrows were operating the Gnat. One of the team postulated that if you removed the fuse controlling the mechanism which limited the roll rate at speed, it would roll faster and they could do some very impressive twinkle rolls with it. This indeed worked, and the team had their engineers remove Fuse 13 from the team aircraft.

Shortly thereafter, 'management' got wind of this and promptly ordered the fuses be replaced, as it was known by the designers that high speed rolling manoeveurs could overload the fin and lead to it falling off. However, they did not order that the fuses were replaced serviceable, so the team had the engineers replace the fuses with blown ones, and continued with their twinkle rolls.

Unfortunately all this came to an unfortunate end when one of the team aircraft shed its fin at low level and the crew lost their lives, after which all the fuses were replaced with serviceable ones.
 
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It'll stop the pump running, which just might prevent it from burning out and making the repair more costly

With a serious ABS fault, it already is. The brakes (though not the ABS) will work normally, so some might say it was reasonable to drive it to a place of repair. Pulling the fuse might reduce the risk of an uncommanded malfunction whilst doing so.

For similar reasons, I'd consider pulling the ePAS fuse if I had to drive a car with an intermittent power steering fault to a place of repair.

If the motor is running in the abs pump then the system is seeing low pressures in the brake circuits, killing the pump if there is a pressure problem may well make the brakes inoperable.

If you’re really going to park the car up and not use it till the brakes are fixed then there is no need to worry about the pump burning out just disconnect the battery.

But my assumption here is that the car is still in use hence just disconnecting the battery not really being the solution the op wants.

Removing the fuse and killing the pump would mean that If there is a pressure low problem it might make the car even more unsafe to drive
It’s likely that one of those solenoids is partially stuck open hence the pump always running.

In pointing out the removal of the fuse being a Mot/safety issue what I’m saying is you can’t just pull the fuse and the noise from the pump stops therefore the car is now safe. The ABS may not be operating safely if solenoids are stuck open. Driving it with the fuse out might leave you with no brakes.




I didn't say this,

That’s why it’s in a different paragraph Edit :: now I know what you mean I misread the context.

Yes if the fuse had blown that would be terrible.....

Although in this situation I think it would make the car more unsafe
 
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Haynes gives no wiring diagram for the ABS system.
Fiat eLearn manual gives a good description of its operation, which I have printed to pdf and is attached.
Strangely it does not mention testing the pump with first ignition on, which it must do, as this is a key test.

The ABS system should do a self-test when the ign is first turned on, which should include a pump test. If all is well, it will sit, silent, unless needed. There is no pressure in the system, unless the brake pedal is pressed, so the pump is not monitoring or trying to maintain any pressure. It would appear that all control is within the ABS ECU, which is part of the ABS unit. There must be relays in there, and I guess the pump relay is stuck. Getting inside to diagnose and replace this relay could be a challenge.
A used unit is a risk. It needs to be fresh from its donor, so that dirt or moisture ingress is minimised.
There are specialists that remanufacture these, a simple Google search for abs repair brings up a list. Here are a selected few. If mine, I'd be getting mine refurbished by one of these specialists.
https://www.ecutesting.com/product-catalogue/fiat/500/abs-pump-ecumodule-combined/
http://www.bba-reman.com/gb/content...a_reman_bosch_teves_lucas_and_all_other_types
https://www.atpelectronics.co.uk/pages/abs-module-repair.html
ECU Testing has been around for a while, and has been used by people on here. Not heard anything bad.
BBA Reman is often recommended on here.
ATP are good people, were one of the first into ECU repairs. They are part of a large autobox repiar company that many manufacturers use for their 'factory' reconditioned autoboxes. The autobox reman operation is exceptional.
 

Attachments

  • ABS.pdf
    303.5 KB · Views: 30
https://youtu.be/-IUZWwMm7nY

This is a very good explanation of how basic abs works , especially the function of the pump in reducing pressure to the wheel brakes.

Does not cover stability control system, or emergency brake assist systems.
 
As jrkitching has said, the ABS system is generally problem free, so if you need a replacement a used pump might be very reasonably priced.

Obviously the question of why the pump still runs with the fuse removed is that the fuse you’ve removed is not the right one.

Fiat are known for having different fuses in the slots for what you’d expect or what’s labelled so you would need to try other fuses to find out which one is the right fuse that’s powering the unit.
Though even then the question is just removing the fuse is not going to achieve a lot and would make the car an MOT failure and therefore would potentially invalidate the insurance if for example there was a serious accident and the car was inspected as a result and they found the fuse for the ABS missing

Thanks. You misunderstood me, sorry. I am not driving the car with the fuse out. It was purely part of my diagnosis as to why the pump is running continuously. The car is parked outside with the battery disconnected. I would never drive a car with a known fault like that.
 
Thanks. You misunderstood me, sorry. I am not driving the car with the fuse out. It was purely part of my diagnosis as to why the pump is running continuously. The car is parked outside with the battery disconnected. I would never drive a car with a known fault like that.


Fiat do mislabel fuses so it’s likely what you’ve removed is not the ABS fuse, maybe one of two ? The ABS computer would use very little power, but the pump would use quite a lot so maybe on its own fuse
 
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