not sure why anyone hasn't answered this post yet but here goes anyway...

E26 - O2 heater sensor error
E31 - Electronic Control Throttle control error signal

first i would check the relays in the relay box and make sure they are updated to the latest ones... (old ones are black, new ones are green) There is an ETC relay in the box, swap it out with the fuel one as it is not used if this is an LPG truck.

second, check the wiring harness at the plug near the components in question and make sure there are no wire breaks , they are well known for breaking wires near the connectors where they plug in. The o2 sensor may just be flaky and replacing it usually fixes that.

If none of these suggestions yields you any results then you will have to investigate further.