Cruise Control Fault

[BlueRubber]

Hi, my cruise doesn't work (2002 V70 2.4 n/a auto)

Problem:

- Cruise button intermittently doesn't not activate "cruise" light or cruise control in general driving.
- it often works at the start of the journey and then won’t work later on.

What I have tried:

- Steering wheel controls are working as radio controls work.
- Have tried pulling brake pedal up as well as down and no effect.
- Have checked brake pedal sensor and it looks undamaged and the brake light works correctly
- Checked VIDA and there are no relevant errors

May be relevant:
Cruise control has always worked previously with my car and it stopped working after fixing a vacuum leak, see this thread for more info about that:
https://www.volvoforums.org.uk/showt...14#post2504814

[SwissXC90]

Check the button and brake pedal switches in VIDA

Do live monitoring and then press and release button a number of times, makes sure the button press is always registered

Likewise for brake pedal

[BlueRubber]

Originally Posted by SwissXC90

Check the button and brake pedal switches in VIDA

Do live monitoring and then press and release button a number of times, makes sure the button press is always registered

Likewise for brake pedal

I tested the cruise control switch and that works reliably.
The brake pedal position reads 0.39% with the engine running ( foot off the pedal ) and responds to brake pedal pressure going up to 50% with hard pressure on the brake pedal.

Does this mean the brake pedal sensor needs replacing or just adjustment?

May also be worth adding that the brake pedal occasionally makes a hissing noise when releasing the pedal.

[BlueRubber]

Screen shot attached of engine running and foot off brake pedal.

[BlueRubber]

Cruise control has started working again, no idea why, but I'll take it!

[GreenBrick]

Mine went intermittent and it was the brake position switch that was failing.
It was on and off for a bit then failed for good.
Over £100 for the part. Typical part that wears away with use, like the pots on the throttle body.

The hissing is the servo, I think that is normal.

[100K+]

I don't know if this is applicable to Auto boxes but in the manual car there is a clutch position sensor which is a simple potentiometer, which gives incorrect readings causing the cruise control to fail.
A simple solution is to solder a resistor in parallel in the sensor to bring it back into range.
I have done this twice on two vehicles and it lasts for about 4/5 years before it fails again, and in my case I bought a new sensor.
Don't know if the brake pedal sensor is the same potentiometer variant - worth a check for a 10p fix - although Maplins has now gone bust.

Cheers
Bob

[BlueRubber]

Thanks for the input.

As far as I know the brake pedal has two sensors.
One is the brake light switch which seems to work fine.
The other for the brake pedal position sensor, I think this is what might be causing the problem, so if the cruise control plays up again I will try changing this sensor.