The general meaning of the U1003 Code is not helpful and the U1003 engine code appears a kind of network problem. The car engine system services specially advanced hydraulic lifters for the U1003 code intake and use valves. The lifters can be distorted by unlocking an internal locking pin. The locking pin is detached using solenoids to alter oil compression fed into the lifter. The oxygen sensors on your car check the oxygen in the finish to control how rich or thin the ratio of fuel and air are in the cylinders. The dictionary meaning of the code is available online.