Hi George,

I agree with Alfredo, you need to look at the hardware. Perhaps P2 is also to select a bank of external memory (or rom). The interrupts are disabled to prevent interference (timing or hardware again). And as Stefan said, after reading xdata things are put back as before. Whatever is read is then sent out on the transmit line. I would guess you've just done a lookup for some control parameters.

By the way, have you searched the web for others who have hacked the same ECU?

Dennis