Hi, anyone have a MAF voltage to air flow chart ? I've got a seemingly failing flow meter that I want to verify. The sensor has a flat 5 pin connector with a built in air temp sensor.

The voltage pattern on this is odd. On the working OEM unit, with low air flow the voltage is ~ 4.00VDC , WOT is 0.98 VDC. ( Checked at the MAF connector ) Usually voltage rises with greater air flow. I've cycled through the settings on my automotive scope and is does not look to be frequency or duty cycle output.

The aftermarket one ( Standard Motor Parts, a good brand ) voltage will fall to zero only when _hot_. Motor will idle but not go over 1500 RPM, acts very lean, check engine will be on. Swapping with a known good unit many times, shows that the aftermarket one is the problem. )

I've been through 2 aftermarket units and want to make sure there isn't a car side problem. I've been in electronic situations where the machine side suffers a failure limiting range preventing a slightly different part from functioning properly. (RE: the slightly different part would work just fine on a machine that was 100% )

Thanks

Update on the MAF hookup, found the source of the inverse readings. ( but not why replacement MAF was failing )

Back in Nov I added wires to the MAF 5V reference voltage and MAF output terminals, when I checked the voltage yesterday I forgot that the test hookup was 2 voltages not power and ground. Checking each to ground made for believable readings.

Tested today with the good MAF I get 4.99 VDC for the reference and ~1.43 VDC at idle.

I also found my old notes:

10-27-13
Good sensor ( voltage rises with higher air flow )
Measuring pin 5 / air flow sensor output.
Key on, engine off 1.0 VDC
Key on, engine running at idle 1.4 VDC
Key on, engine running at elevated speed 2.0 VDC


Bad sensor during problem ( voltage falls off with increasing air flow )
Key on, engine off 1.0 VDC
Key on, engine running at idle 0.95 VDC
Key on, engine running at elevated speed 0.45 VDC