Xantia V6 - Speedo/suspension link?

f00lzz · Unread post by **f00lzz** » 24 Nov 2008, 07:22

Hi everyone.

For a few months now, my Xantia V6 has occasionally lost it's speedo reading... just drops to 0 for a few miles and eventually flicks back up. This doesn't cause me any problems as such, except that I recently was on a fairly long run travelling at 70mph (honest officer) when it did it's usual drop to 0... this coincided with what I can only describe as a definate increase in tyre noise and a sensation of harder suspension accopanied with a 'booming' noise which actually hurt my ears!! Sure enough after about 10 mins of this I noticed the speedo start working and the booming noise stopped.
I wasn't aware of a connection between the speedo operation and suspension! Can anyone offer suggestions as to the cause?

Ian

Unread post by **CitroJim** » 24 Nov 2008, 07:59

Hi Ian,

The Speed sensor feeds into both the Hydractive ECU and engine ECU. The loss of signal would have at best led the ECUs to use a default speed setting and in the case of the HA ECU, might well have set the suspension into hard mode - hence more tyre noise.

The Engine ECU uses road speed as one factor in the calculation of mixture so if the sensor input fails, it's a fair bet the ECU will either use a default value or run into "Limp Home" for a bit.

In any case, I'd be tempted to to seek out a Lexia and have a look-see in the ECUs. It's an odds-on bet there'll be stored faults in both now.

Check the connections to the speed sensor (should be in the vicinity of the final drive on the gearbox) as it's a pretty hostile place.

f00lzz · Unread post by **f00lzz** » 24 Nov 2008, 08:07

Thanks for the speedy reply (no pun intended) I'll have a look for the speed sensor next time I can get the Xant over my brothers pit...

Cheers
Ian