Mac Pro 1,1 Apple Diagnostics code help.

I don't know what the letter codes mean, other than the important one (or two, depending on what you see)
4MEM means there's a test failure in one of the memory sticks - or one of the memory slots.
The two digit number directly after that should help guide you to the suspect stick or slot.
So that leaves you with several things you can try:
Reseat the RAM sticks, making sure that the memory configuration is correct (using correct pairs of slots)
The Memory Slot Utility will help you decide if that needs some attention.
You can find THAT in your System/Library/CoreServices folder (look for it, it does exist, all Macs have it installed, but the Utility only works on a MacPro )
Reseating means actually removing the sticks, then re-inserting in the same slot (assuming that's the correct slot.
Run the test again, twice.
There's an extended test option, so you should also run that. Expect the test to take a long time if you have a lot of memory installed. The extended test may actually pass when the standard (short) test fails.

If you still get the same errors, referring to the same couple of slots (44 or 46), then try moving one pair from other slots to that pair of slots, then run the test again.
Be sure to try OTHER memory in those slots, too. (borrow or purchase. Check for return policies if you buy, as it may turn out not to be a memory stick.
If the same slots fail again, then you might have a bad memory riser card. Be sure to try swapping the riser cards between upper and lower positions. If you get memory failures with the same slot codes, after swapping the riser cards, then you may have a failing logic board - maybe.

I should also ask the question:
Other than the diagnostics failure - are you actually having a problem with using your MacPro?