I have the LM1 meter with the RPM cable. I want to data log the Mass Air Flow sensor voltage (0-5 volts) that the ECM sees to determine air flow. When hooking up any sensor information to the RPM cable, you need to have a signal wire (0-5 volts) and a ground wire from the sensor for the most accurate readings.

My car is an '87 vette. The MAF sensor has 5 wires going to it. There is a 12 volt feed from the power relay, another power feed from the burn off relay, a signal wire (0-5 volts, which I will be hooking up to the RPM cable), and TWO ground wires. One is labeled as a "System Ground" (which looks like it is part of the engine ground loop) and the other is labeled as an "Analog Ground", which seems to just go to the ECM.

My question is, which one of these ground wires should I use for the connection? Does it matter?

Thanks!