I am working to get the MS2 going with MAF instead of speed density, but having problems getting a signal from the stock MAF.
Here is the relevant schematic from the NB 99/00 ecu.
I started by verifying signal at the MAF connector. Three wires on maf plug, ground (black), +V (red/white), output(green/blk)
With black as ground, I am getting +14v on ref (good), and at idle the output of the MAF is 7volts.
According to the schematic, this 7v green/blk signal should be carried through to pin 2L on the ecu.
However, I am getting 0V when I read from 2L at the harness. If I unplug the Megasquirt the engine runs fine with the stock ecu, so I believe the MAF is good (recently passed emissions in this configuration.)
Am I misinterpreting the schematic? The green/blk carries through to pin 2L so there should be the same voltage as read at the MAF?
The thing that is strange is that at idle the MAF is showing 7v? The megasquirt ADCs expect logic level 0-5v and I would assume the stock ecu would expect the same.
Any suggestions on what is happening appreciated. I hesitate to connect the MAF output to the MS2 because 7v is not logic level. Is it possible that as flow increases, voltage drops? (output might be 0-7v) Or does voltage increase with flow?