with the engine running go to the front of the car and push down then go to the back of the car and push down. the car should go down then you should hear the pump kick in and lift the car back up. if when you push down it just wont move then youle no if its front or rear sphere,s. next do side to side and if one side wont go down then thats the side thats gone. if both sides wont go down then it will be the stiffness sphere