B is ground.
C should be 12V until you pull your PCM fuse. It'* paralleled off the PCM 12v supply voltage from the fuse (now I don't have my manual to tell you....hang on, have a cheapy here.....)
BD14 is in the orange connector on your PCM, yellow wire in slot 14. Read the voltage with it connected, you're just probing inside the pin to see if it'* the same 4v as you read on PinB of the MAF connector (unplugged). It'* the other end of the same wire. I'm trying to see if the PCM is sending the correct voltage to the sensor to begin with, indicating a wiring problem. Please do not read pin A to pin C on the MAF sensor. They are fed from different sources.
Pin B is ground for the sensor. It needs to be read to a good chassis ground (sensor disconnected).
The car can be running or just the ignition on (motor off) if you know your battery is fully charged, but I'd prefer motor running. Make sure your meter is on DC volts for the voltage checks, and OHMS for the ground check.
Check voltage from MAF connector pin A to ground. Tell us what it is.
Check voltage from MAF connector pin A to Pin B. Tell us what it is.
Check voltage from MAF connector pin C to ground. Tell us what it is.
Check for resistance (ohms) from MAF connector pin B to ground. Tell us what it is.
Check voltage at the PCM Pin BD14 (yellow wire) and tell us what it is.
Pin A to ground is the sensor reference voltage, and should be 5V.
Pin A to B is the same reading using the MAF harness ground to see if there'* a difference.
Pin C to ground is the 12V sensor power (used to heat the filament). It'* the same source as the PCM voltage source, and comes from the same fuse.
Checking resistance of Pin B to ground verifies the readings found so far.
PCM BD14 tells us if the Pin A to ground is low, whether there'* a wiring problem or if the PCM is the problem in sending a signal too low to begin with.
I need you to tell me these with NO other combinations. If I'm to help you with your problem from hundreds of miles away, I have to know what these numbers are.
The PCM is located above your RF passenger feet. Remove the hushpanel (plastic sheild under the glovebox area) and find the silver box. The orange connector on it should have a yellow wire in pin 14.