Technical Panda 2004 Multijet self braking

[pgainf]

Greetings!

I have a Panda Multijet 2004 (October, so before ESP units were installed).

The problem that I have with the car since I bought it (last year) is with the brakes.

The car sometimes starts braking slightly.

I already changed all braking accessories.
Brake pads, discs, tubes, brake fluid. Even the brake lights switch.

After changing all that I notice that if I don't connect the brake light switch the car works perfectly.

So must be something related to the ABS. The problem is electronic for sure.
The car does not have ESP.
But it does have 4 wires for braking and a 4 pin plug (usually only used for 'Dynamic control' or in other words ESP).

The Fiat dealer has no idea what's the problem.
They say they never saw it before.
I bet they want to change all and then charge me big time.

What can I do?

Any help would be great!
Thanks

ps. I'm starting to think next time I will buy something Korean.

Someone with the same problem:

For no apparent reason my Grande Punto (1.9 Multijet) applies the brakes and stops during journeys. If I turn off the engine and wait 5 or 10 min you can then drive again. Have changed the brake hoses, the Calipers and had it checked on a number of occasions by Fiat and Halfords. No one can find the problem. It is quite an issue as they come on very quickly! Anyone had the problem or can suggest a solution?

http://www.honestjohn.co.uk/forum/post/index.htm?t=94411#m1040137

 

[Most Easterly Pandas]

But it does have 4 wires for braking and a 4 pin plug (usually only used for 'Dynamic control' or in other words ESP).

Sounds like the ABS system, as you state your unlikely to have ESP, was only ever an option in most markets.

When does it self brake

 

[pgainf]

It breaks every few minutes.
The feeling is like driving with the handbrake on.
The instant computer fuel reading goes up showing the car is going forward with extra effort.

It's a crazy problem...

 

[Most Easterly Pandas]

Have you tried putting your foot under the brake pedal and pulling it back up to see if that releases the brakes?

 

[pgainf]

The brake pedal is totally up.
The problem only happens if the brake lights switch is connected. If not the car behaves normally.
I'm sure it is not mechanical.
Perhaps is some abs sensor or anything that triggers braking.
Do you thing it might need a new abs ecu?
It must cost a fortune...

 

[Most Easterly Pandas]

Might be worth disconnecting the ABS ECU to see if it still happens. Will flag ABS fault, but brakes should work as usual

 

[AB100]

This might sound dumb but I think I'd want to 'test' the ABS before doing anything.

Presumably you're in England and therefore within a few miles of a wet road. How about you take the car up to 30mph and jam the anchors on - see if:

1. The ABS light comes on (I assume we have one)

2. You feel the ABS 'judder' through the brake pedal

 

[Popshot]

Are you sure it's the brakes coming on and not the power being cut to the engine? If the brake light switch is activating the brake lights without the pedal being operated due to a faulty switch or it being badly set then the engine ecu will become upset about both power and braking being needed at once and throw a wobbly. Could be as simple as repositioning or replacing the switch. If still using the car test the ABS so you know if you can rely on it or not. If the ABS is not functioning then you'll loose nothing by disconnecting the ABS ECU until you get a proper fix.

 

[richardllew]

I was going to suggest removing the ABS fuse, but this also has the stop lights on it. Not a good idea.
My Haynes manual shows an electrical connection from the brake switch to the ABS unit, so it seems you're on the right track.
If you disconnect the lead to ABS unit or disconnect one ABS wheel sensor then this will stop the ABS functioning, and hopefully will prove beyond all doubt that it is the ABS unit or sensors. Sensors will not normally cause this problem, but then again its not a normal problem.
ABS is a split system, and each wheel is controlled independently, how about driving a bit when its braking and see which disc/drum gets hot. Don't burn yourself !!!
Let us know how you get on !

 

[pgainf]

Thanks for your advice!

I did try today to remove the ABS fuse.
In my car the ABS fuses are 2.
One small (F42) which is a 25A fuse, that after removing it even the speedometer didn't work.
I drove the car for a few miles and it didn't count in the odometer. The car was also very strange. The steering wheel was very light and less power coming from the engine. So I put it back on again.
The second ABS fuse is a very big one. 60A named F02.
I kept that one off. In the instruments panel the Abs warning light is on and the handbrake light is also on.
The car seems to work normally. No problems until now with self braking and even the brake lights work.
But no ABS. If I break hard, the car just makes hard braking noises from the tires and it even dances a bit.
I will continue to use the car without the ABS big fuse on to test it a bit more.
Do I really need a new ABS ecu? Sensors?
It's awkward, the ABS before worked ok but it would start to self brake only if the brake light switch was installed.
I will ask a friend who have a obd2 machine reader to check for errors on the ECU. He uses it with his VW car. Hope it works with my Panda also.

Thanks for all the input.

 

[Most Easterly Pandas]

Do NOT run about with the ABS fuse removed! It'll probably control more than just the ABS, which could lead to an accident!

Simply disconnect the ABS ECU (under the pump) to disable only the ABS

 

[richardllew]

My Haynes manual says F87 (7.5amp) is for the stop lights and ABS. This must just be for the electronics.

It doesn't mention a 60 amp fuse, but the ABS unit includes a powerful electric motor that will take around 60 amps.

It looks to me that the wheel sensors are working ( as you've got a speedo which is most likely driven by one sensor).

The ABS releases and re-applies individual brakes when the a sensor senses that a wheel is slowing down too fast. So it could be the ABS pump which is applying one brake.

The only other possibility is the servo is somehow applying the brakes, but as removing the stop switch stops the problem it can't be that.

Removing the ABS plug will leave the connections open to moisture, so I don't think removing the fuse is too bad. Not as bad as brakes that apply themselves.

I would guess its the ABS unit that is at fault, but get the diagnostics on it !
What a long post !!!!

 

[richardllew]

Just re-read popshots post, and while I think its the ABS don't discount his idea.

These systems all interact with each other. When I coast to a stop on my MJ with the engine idling the engine note always changes at about 5mph, I think the engine management system is reacting to the speed sensors.
Things are getting complicated !!!!

 

[Most Easterly Pandas]

Another idea. Was this Panda affected by the ABS recall? If so has it gone in for the recall?