V70 2004 Brake assist service required

[ritchie71]

Hi there,

I have recently purchased a 2004 V70 2.4 D5. Sometimes when I drive the car I get the "Brake assist service required" message and when that happens I cannot activate the cruise control. When it happens I also get the ODB2 scanner code "p0571 brake switch A circuit".

From what I have read so far it seems this would be responsible for the cruise not working because it needs to know when you have pressed the brake.

The car has no issues with its braking, the switch that operates the brake lights seems to always work and the lights come on when I test. So I am thinking that the issue is not with the brake pedal sensor itself. The error does not show sometimes. I can go for a drive for over an hour and no problems, then other times it just does it immediately when I turn the ignition on.

Some further reading suggests it might be the brake pedal position sensor at fault. I was wondering if anybody here knew what the "A" circuit specifically referred to in the error code? If I can confirm it is the brake position sensor then hopefully an easy fix.

One thing I have noticed... If the error message is persistently showing, then putting my foot on the brake with the ignition off, and then turning the ignition on will stop the error. Of course I cannot move the car with my foot on the brake , as soon as I release my foot from the brake will prompt it immediately. Not sure if this info helps in the diagnosis in any way.

I will be doing an 10 hour drive next month and would love to know the cruise was going to work.

[VOLVOBOY]

https://www.justanswer.com/volvo/a6k...-light-on.html

This link was answered by a Volvo Tech .
Says it is the switch in the servo and how to replace it.

[ritchie71]

Originally Posted by VOLVOBOY

https://www.justanswer.com/volvo/a6k...-light-on.html

This link was answered by a Volvo Tech .
Says it is the switch in the servo and how to replace it.

Excellent thank you!

Looks likely it is the brake position sensor after all then.