How to test HFM/tell if it functions properly

[Volf]

Curious if there is a way to test the HFM to see if it works properly. I searched the topic and all I got was a bunch of MAF codes threads.

[Balthazarr]

Should be battery voltage at pin 3 and 3Ω-4Ω at terminals 5 and 6 and gnd at pin 1.
Receives battery voltage through the DME relay.
I think the numbering is cc looking at the connector along the harness although I expect the pins are numbered inside the connector as most are.
If you mean the HFM itself, it either works or doesn't, AFAIK.
A flow bench might work, however, you have to have a way to monitor the signal and provide the reference signal for comparison.
As for flow capacity, there will be no change to compare, obviously.

[///M3 CRAZY]

at idle the yellow wire should show 1 volt. and as you rev the motor it should rise. no more then 5 volts.

[Volf]

Now that I think about it, couldn't I just unplug the MAF and see if the engine reacts?

[thejlevie]

There are two possible failure modes for an MAF. The easiest to diagnose is complete failure of the unit, which normally results in a DTC code. The more difficult fault to diagnose is contamination of the thin film sensor within the MAF which results in erroneous data. This is typically a result of oil or other organic contaminates from an oiled air filter or one so open that it allows "road trash" through the filter. One way of diagnosing this fault is swapping in a known good sensor. On OBD II cars, looking at the live data from the MAF can diagnose a contamination issue if it is significant. Other than those methods you'd need a flow bench and the reference curve for the MAF.

[Volf]

the only reason I ask is because my 3.5" conforti intake and 540i HFM get here tomorrow and I wanted to check the MAF before I installed it.

[Volf]

:help