Emergency Brake Assist Failure

[davek_964]

Bought my 2006 Vantage on Saturday, and up until this morning have been really impressed with it.

But while stopped at traffic lights this morning, I suddenly got a warning pop - Emergency Brake Assist Failure. Not great after only 5 days of ownership!

A quick search suggests it's relatively common, and is a sensor at the bottom of the brake master cylinder. One comment I found said it's a 10 minute change, although I can't find anything that says what's involved.

Anybody know? Given it's function, I assume that changing it would actually involve needing to bleed the brakes again afterwards.

[davek_964]

KnowsAnAston said:

It won't be the brake light switch causing the issue. I'd get the pressure sensor in the master cylinder changed first, it's most likely to be the problem.

Yep, that's what I assumed - I've ordered one this morning. It's happened 4 or 5 times now, so I guess it will be obvious fairly quickly whether it's solved it.

[davek_964]

Bouldermobile said:

Just for clarification purposes: the 'Pedal Travel sensor' is a roughly cylindrical shaped part attached to the brake servo (located under the bonnet) as opposed to the 'Brake Stop Light switch', which is located in the car and attached to the pedal box assembly. However, I do concur with Dave that it won't be the Brake Stop Light Switch.

Not sure if the Pedal Travel Sensor and the Pressure Transducer both work with the Emergency Brake Assist system so do let us know how you get on!

Are we talking about the same thing? The transducer is also cylindrical and is attached to the bottom of the master cylinder. Item 4 in the diagram here :

http://astonmartinbits.com/models/5-V8-Vantage/par...

That's what I've ordered anyway!

[davek_964]

Cool - if number 4 doesn't solve it, I'll try number 13!

[davek_964]

On Thursday, the failure came up again - both times I used the car (morning / evening). It hadn't shown for about a month, so I hadn't fitted the new sensor yet.

I changed the sensor Thursday evening and that seemed to cure the problem - until this morning. The failure has shown up again, so I guess it's not the sensor.

So, it might be the pedal travel sensor after all. Will need to investigate further.

[davek_964]

huggy1 said:

Mine did the same last year. I have the RAC parts and labour warranty (costs about £80 for £750 worth of cover per fault). Got recovered to the dealer and they changer both front ABS sensors. They are only about £30 each and look simple enough to change but it's diagnosing that's the trick on this one.

Did that give you EBA failure but nothing else? I assumed I'd get ABS / traction failures as well if it was an ABS sensor.
I suspect I may have to take it to a dealer to get them to have a look - hopefully their diagnostics will give more info.

[davek_964]

wafu1983 said:

Can you elaborate a little on how you fitted the sensor? I have just ordered a Brake Pressure Transducer too, although in my case I am looking to fix a 'DSC Service Required' message. The sensor is easy enough to access, but I am concerned that needing to bleed the brakes afterwards might be beyond my abilities. Also I wondered if changing the component would also necessitate some kind of diagnostic system input?

I was worried I may have to bleed too, but found threads saying it was a 10 min job so figured that couldn't include bleeding.

First warning - the sensor part means you cannot get a normal socket on it - the sensor connector is too deep unless you have a deep socket of that size (which I didn't). I tried an adjustable spanner which was too long for any movement and I nearly gave up - then remembered I had a small toolkit I keep in the car and that had a shorter adjustable spanner in it.

I lost very little fluid when removing the old sensor - in fact I'd say the only fluid that came out was what was in the sensor itself.

I filled the new sensor with fluid so that I wasn't introducing air, then just tightened it up.

My fault is intermittent so I had nothing to clear.

[davek_964]

With these feet said:

Have you had the fault codes read with AMDS? It is quite specific as to which sensor is at fault, if it is one.

Had a Vantage in a while ago with emergency brake failure lights on, checked through all the easiest options but ended up being the ABS unit itself that was at fault. Unfortunately not a cheap job, £800 ish in parts and about an hour to change.

I'll hope it's not that then!

My fault comes and goes - I assume they would need to read the codes while I actually have the fault showing? That would be difficult unless it gets much worse than it is now.

[davek_964]

The brake pressure transducer is simple, but see my previous post about spanner size.

I'd be interested in how you get on with the pedal travel sensor. As far as I can see, it has a vaccuum pipe attached to it, so it is more than just a simple electrical connector. I've not looked at how easy it would be to replace though.

[davek_964]

Mine came on again this morning when I started the car. Interestingly, taking the key out doesn't seem to clear the code but locking / unlocking does.

I am debating whether to give the pedal travel sensor a try or just accept defeat and take it to a specialist to see if they can figure it out.

[davek_964]

Took it to a specialist today, and the fault it's logged is pedal travel sensor.

They asked when the brakes were last bled because they said that sometimes this fault is actually due to air in the system - the pedal travel doesn't match the braking force so the sensor fault gets logged. They said that if that's the case, it tends to happen more under heavy braking.

So, initially we decided I should get the brakes bled and see if that cures it before getting the sensor replaced. But having thought about it, heavy braking is probably the one situation it hadn't happened and sometimes it's immediately after system check before starting the car or touching the brakes. Since the sensor is pretty cheap anyway it's booked in next Friday to have the sensor replaced and the brakes bled.

I would expect to be able to do both myself, however I still have to decide whether I continue AM service history or use an independent next year when my first service will be due. I've been impressed by this independent the few times I've spoken to them and when I visited them briefly about whether my windows were dropping correctly when the doors were opened.

So I think this will be a relatively simple and not too expensive trial run of their work (Spellbound in Farnham).

[davek_964]

Light came on again this morning - apart from the times it's done it from startup, it's actually the first time I've noticed exactly when it appeared.
I'd previously used the brakes, but only gently - from a speed of about 10mph. Crossed a junction and a few seconds later the light came on - so maybe 5-10s after I'd last used the brakes.

Hopefully, it will get fixed on Friday afternoon with the new pedal travel sensor and brake bleed!

[davek_964]

I don't know what the codes mean I'm afraid - however, I would say that when I tried reading codes from mine with Torque, it didn't display any codes so you've managed more than me.

My failure hasn't come back since having the pedal travel sensor replaced.

[davek_964]

BewickPlace said:

Were you using the paid version of the app? I had to upgrade in order to access the ABS codes - now I can see the code I don't know what it means :-)

Ah, good to know. I was using the free version.

[davek_964]

PrAston said:

I replaced the transducer (no bleeding required thank god), and have driven the car through at least 6 or 7 stop/start cycles, but the message has yet to clear. How long should I give it before I start looking into other possibilities?

You should already be looking. Mine cleared each time I stopped / started the car and only came back when braking.
Is yours permanently on? If so, that seems odd.

Mine was the brake pedal travel sensor - but as I say it cleared when I turned the car off and only came on again when braking.

[davek_964]

If the car is showing the warning, surely it's logged a fault which tells them why?

[davek_964]

sundayjumper said:

davek_964 said:

If the car is showing the warning, surely it's logged a fault which tells them why?

Depends.... the car will log some errors, but it may take some investigation / experience / luck to find the actual fault.

Example: my old BMW once threw up an engine warning, and on reading the codes it said there was a fault with injector 1, injector 2, injector 3 & injector 4. Four new injectors from BMW are a lot of £££s.

But if I had replaced all four injectors that wouldn't have fixed it, because the actual problem was that the wiring to *one* injector had come loose, rubbed against the fuel rail and was shorting out. Actual repair cost - some of my time, and a couple of inches of insulating tape.

Beware of "computer says...." !!

Absolutely - but I'd want any faults fully investigated before spending that kind of cash on an ABS module!