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Hi all,

Can I ask for some advice. My 147 JTDM has been throwing up ABS and VDC failures which also throws off my ASR and most frustratingly my cruise control.

It seems to only occur when I press the brake pedal (even pressed at rest) so it's not showing up when I start the engine.

I have just got the car back from my local mechanics but they aren't Alfa specialists. My battery voltage reads as normal and all the fuses are in order. I have read through previous forums and some mentioned it being the switch on the pedal? or perhaps a sensor on one of the wheels?

Can anyone offer any advice before I take it to a Specialist?

Thanks in advance
 

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It's likely to be the brake pedal switch that has failed, which is mounted behind the brake pedal. These are cheap and easy to fit - it just twists out of the mounting bracket. There are plenty of threads on here about it. You can get a replacement from most specialists - shop4parts or Alfaworkshop etc.
 

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Although it seems to respond to pressing the brake pedal.......
Is that because the ABS/VDC control module sees the brake line pressure rising as you press the pedal, but isn't seeing the brake switch because it has failed?
 

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Is that because the ABS/VDC control module sees the brake line pressure rising as you press the pedal, but isn't seeing the brake switch because it has failed?
or the other way round.... It sees the brake pedal being pressed, and then subsequently discovers a problem with the ABS ....
 

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The brake light switch has two sets of contacts. Over time one set suffers from corrosion on the contact faces which gradually builds up to the point where the voltage drop across it is so high that the ECU doesn't see the switch as "made" when the brake pedal is pressed. As a result of this the ECU is seeing a conflict between the two sets of contacts.

Dismantling the switch & cleaning the contacts will improve matters, but the switches are so cheap that replacement is the best option.
 

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The brake light switch has two sets of contacts. Over time one set suffers from corrosion on the contact faces which gradually builds up to the point where the voltage drop across it is so high that the ECU doesn't see the switch as "made" when the brake pedal is pressed. As a result of this the ECU is seeing a conflict between the two sets of contacts.

Dismantling the switch & cleaning the contacts will improve matters, but the switches are so cheap that replacement is the best option.
Thanks, R.T.
 

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Discussion Starter #8
Thanks for this guys,

I had a play with the brake switch today, that seemed to cure the problem for a time after an hour or so of driving I was parking the car and then the fault appeared again.

I restarted the car and fault gone until I press the brake. Again it's not everytime. Seems very intermittent. I'm guessing a new switch or sensors on the wheels.

I appreciate all the info though.

Cheers
 

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Try reading the error (or getting it read), that should give you more specific information....
As you get the error standing still, likelyhood of it being a wheelsensor is very slim.....
 

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I restarted the car and fault gone until I press the brake. Again it's not everytime. Seems very intermittent. I'm guessing a new switch or sensors on the wheels.
The brake light fault is, in my experience, caused by high resistance across a pair of contacts, so it will be voltage-sensitive. Voltage is dependent on a number of factors, such as engine revs, electrical load, etc., so it will be intermittent.

Try reading the error (or getting it read), that should give you more specific information....
As you get the error standing still, likelyhood of it being a wheelsensor is very slim.....
A faulty brake light switch doesn't produce an error code. (Well, it didn't on my 147!)
 

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Hi all,

Can I ask for some advice. My 147 JTDM has been throwing up ABS and VDC failures which also throws off my ASR and most frustratingly my cruise control.

It seems to only occur when I press the brake pedal (even pressed at rest) so it's not showing up when I start the engine.

I have just got the car back from my local mechanics but they aren't Alfa specialists. My battery voltage reads as normal and all the fuses are in order. I have read through previous forums and some mentioned it being the switch on the pedal? or perhaps a sensor on one of the wheels?

Can anyone offer any advice before I take it to a Specialist?

Thanks in advance
Had exactly the same symptoms a while back, pressing the brake pedal brought up the ABS/VDC warning lights. Shop4Parts delivered a replacement brake switch and all is good. Shouldn't be any more than a £15 fix. It does mean moving the drivers seat all the way back, lying face up with your lower back resting on the kick-plate so you can get your hands to the switch. It's not comfortable as your head is right under the switch holder and there's not a lot of room for your hands. But it's an ideal DIY job. :thumbs:
 

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Ho folks, I get that same fault condition on my gt, but only intermittently whilst driving, and only ever when about 50mph.... always clears on engine stop and restart. More likely one of the wheel sensors? I had to run for a short while on a spacesaver on the front right, and I got the error most of the time. Thanks.
 
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