mass air flow wiring

[dstredi]

I have been having problems with the hacked up wiring that came with my ca18det. I bought a harness and ECU and began installation. My new harness is not exactly the same as my old one. My old harness has the correct four wire connecter for the mass air flow. The new harness has a three wire connecter. Any ideas? Thanks, Dan

[elwesso]

could possibly be an extra ground... I know on many later infiniti they added a 4th wire which was a redundant ground.. Just a shot in the dark...

[dstredi]

The wire that is missing on the new Ecu and harness is green with yellow stripe. Pin 37 on the Ecu. I can wire my old plug to the new harness, but I really need to know the funtion of that wire. Thanks, Dan

[alex200sx]

Mafs from ca18det without cat have four wires, mafs from ca18det with cat have three wires. The extra wire is for CO correction.

[dstredi]

Thanks for responding. I would have thought all street engines of those years would have cats. I will assume that I can wire my four wire plug into the harness and just forget about the forth wire. Thanks, Dan

[float_6969]

There were a very few out there that had no cat and not O2 either. The MAFS plug is a 4 wire and there is no wiring for the O2 sensor.

[alex200sx]

The maf in my car has a little screw which modifies air/fuel relationship at idle. All of this can be measure at the fourth wire.

Regards.