Follow up Part 1.
Well, well! As it turns out......the coding of DTCs 1240 and 1241 were caused by a sloppy fitting female receiver terminal at pin #39 in the ECU 81 pin connector of the main wiring harness. DTC 1245 was the result of the same thing at pin #31.
After I checked several things suggested by a senior tech staff member at Komatsu North America and found all those criteria to be OK, it really left no where else to go but to the 81 pin connector.
In my tests I was perplexed that the SST was showing 0 kpa for the LPG pressure sensor and I could not detect the prescribed 2.5 VDC at the sensor connector on the BLUE/black wire that leads to pin #31 at the ECU. I had previously tested all the wiring for continuity and had confirmed there were no open circuits. So I decided to test for 2.5 VDC on this circuit by going directly to the ECU 81 pin connector and testing it "live". This was to be accomplished by inserting a "needle probe" into the back side of the connector body, slipping the needle in between the wire insulation and the connector body till it was in contact with the female receiver terminal. My plan was to observe the SST data screen and test for the prescribed voltage with the engine idling. Voila! With the needle probe pushed in against the terminal.............the fuel pressure on the SST was 27 kpa, and I had the voltage on the VOM. AWRIGHT! I was now able to clear DTC 1245 from the ECU memory but I still had DTC 1241 showing. DTC 1240 was not showing at the time. I studied my notes and charts and proceeded to employ the same technique to other pin positions in the 81 pin connector to see what would take place. I began with the Injector Driver circuit layout and decided I would go from left to right of the Driver wires leading to the ECU. The BLUE wire, pin 39 was first in line. I pushed a needle probe into place and then went directly to the stored DTC screen and cleared DTC 1241. After I started the engine, the MIL was dark, and there were no codes in the ECU memory.
After giving due consideration to this new found data I dug into the bag of connectors and pigtails I salvaged from the other wiring harness R&R job I did in mid-2012. I took that 81 pin connector apart and extracted the wires from pins #31 and #39. I unwrapped the loom at the 81P connector on the truck and extracted wire #31 first. I then took the single wire and manoeuvered it over to the ECU and tested the fit of the receiver terminal to a pin in the ECU and it was so loose that it would rock from side to side. I tested one of the wires I had just taken out of the salvaged 81P connector for fit on a pin and it was nice and snug requiring a slight "pull" to remove it from the pin. I'm splitting this post at this point cause I know it is "over length".