Engine Warning light Help please

Hi Guy's'

Just recently after topping up with oil and power sterring fluid"probably coincidential",the engine management system lights up "cruise control not avalible" and the ecu warning light on dash lights and wont go out, press the stalk, the message disapears,the the engine miss fires wont go above 40mph ,limp home mode, although the hand book says the 2.1 v6 petrol doesnt have this feature, put car in neutral boot the thottle to max revs, and then the car drives ok, but the message is back. plugged a fault reader in code p1111;which Jag web site says is the clear code for all functions,p1000,I then clear all fault codes ,all is then ok for about 20 miles then it starts all over. it's got me beat Help!! please.