My ABS warning light is on constantly,also the cruise control does not work and also the dorrs no longer lock when moving off.
I believe it could be a speed sensor...????

All was well until recently

Where do I start to look.

Check your tires. Worn tires can and will cause that problem, also, oversized tires can cause a asr problem if the ratios are not correct, as well as just replacing the tires on just one end of the car(ie. just replacing the rear tires because the fronts were o.k.)

Thanks, will check this out.