Volvo Repair: ABS/TRACS/Emission Lights On - Loud grinding, high speed network, wheel speeds

Question
My Volvo S60 only has 45,000km on it. All three "ABS/STC/Emision service required" lights came on recently. I brought the car into the authorised Volvo workshop and was told that it was an 'intermittant' problem and that the ABS sensors are faulty. I double-checked with the engineer that it is not the ABS module problem, and was told that it was a faulty ABS sensor.  Sensors were changed but problem was not fixed

The ABS/Tracs/Emission lights do go off sometimes, and sometimes only one of either ABS or Emission lights come on.  About once a day, there will be a loud grinding sound coming from the front wheels. This usually happens within the first few minutes upon starting the car and picking up speed. Starts with "clicking" sounds which turns into "crunching", "grinding" sounds as I step in the brakes. I can also feel the grinding on the brake pad. It usually goes off once I hit 30km/h or above.  Noticed a pattern lately.  When I start, emmission and ABS lights come on.  After driving for a while, the ABS lights go off.  Then when I slow down to a speed below 30km/h, the grinding starts.  The grinding gets louder and more forceful when I step on the brakes.  Once I hit above 30km/h, the grinding stops and the ABS and STC lights come on.  No more grinding occurs for the rest of the trip.

I am going to bring the car in again for another diagnosis.  Would appreciate all the help I need as now the mechanic is saying that it is because of the need to replace my brake pads!

Answer
most common problem would be a bad ABS control module.without hearing the noise I can not say for sure what it is but it could be the ABS activating due to seeing a difeence in wheel speeds.which could be due to bad sensor or control unit.most problems I have seen are the control unit.the emission light could be a seperate problem or a problem in the ABS control unit causing a problem in the high speed network of the vehicle which could affect the engine control unit. i would have it looked at for a proper diagnosis by the delaer if possible.