Delco data link

[Robert W. Hughes]

You say you have a P4 but your description fits the C3. I am just
finishing a PC project like yours specific to the Fiero with a C3 and
can make several comments:
1. The PC cannot directly read the bit string either with a serial port
or the printer port (at least not with DOS running). The ratio of pulse
widths is not compatible with the serial format. Because of the
interrupt system you will lose bits from the printer port. I can supply
a simple circuit to read, buffer, and supply the bit string to a printer
port if anyone is interested.
2.Each engine series (and there are further variations) has its own data
string with byte positions and significance being different. This means
forinstance that the MAT byte may be in a different place in the string
and use a different conversion from hex 00-FF to degrees C/F. I can
supply some of these for pre-88 GM cars.