hello,
it seems mitsubitshi has an hpk bulletin out on this DTC
(so does caterpillar)

the code is set because there is error in LPG air/fuel ratio reading

when truck enters closed loop operation the 02 sensor does not read correctly for a predetermined amount of time and sets the DTC code E-43 and sets the LPG system back to open loop operation. This condition will remain till the cause of the problem is found and corrected.

Now further on in their explanations they refer to the Main Fuel Injector as being the issue because of incorrect injection pulse.

They recommend replacing the LPG main injector, then recheck system and run a FAST TAS relearn and then monitor output of injector pulse and 02 sensor readings. (You WILL need the handheld scan tool or the diagnostic laptop software to perform this task.)

All should return to normal once this is done.

Now what you can try is to clean the main injector first with some non-corrosive cleaner like electrical cleaner and then recheck the system, it could be the injector is just dirty. But if this does change the problem or makes it go away it strongly recommend replacing the main injector anyway, once they start malfunctioning even cleaning doesnt last so replacement generally happens anyway.


good luck