according to the code chart any 03 code is a VCM communication error
their probable causes listed for E03 are
- connector contact bad
- harness bad
- VCM controller bad
- controller bad

now these are just generic possible causes and may not be the actual cause, they just give you general areas to look at.
As kevin said, check the relay box and there are 2 EGI relays that control ecm power and ignition coil. Then there is a MainC relay that controls LP Fuel lockoff, another one ETC Relay that controls the electronic throttle control, and the last one for GAS Fuel Pump Relay (not used on LP trucks but is there)
There should be a diagram of which ones are which in the lid of the relay box.
You can try swapping them around and see if the problem changes and/or goes away. Also if it has the black relays in it those have been updated to a new style relay that is green. When you order the part it will automatically get you the new style as the old ones are no longer in circulation. If this is the case i would replace ALL of them.

good luck :o)