Vehicle Speed Sensor: What does it do?

oscarloco · Unread post by **oscarloco** » 26 Apr 2007, 20:11

Hi guys

After repairing the speedo drive a few weeks ago, I started wondering, what is the Vehicle Speed Sensor function?

I know it has something to do with the ignition, but what?

Unread post by **CitroJim** » 26 Apr 2007, 22:15

Hi Oscar,

Depending on the model, it does several things:

It sends a speed signal to the Hydractive Computer to assist with hard/soft mode change decision process;

In manual gearbox cars it tells the Engine Management to maintain a slightly higher idle between gear changes to ensure a smooth change whilst the car is in motion;

In automatics it assists the gearbox ECU to make gearchange decisions;

It drives the speedo and odometer.

I'm sure it does more than that too but my mind has gone blank!