Editing Z31/SENSORS/afm php (section)

=== Differences ===

There were two different Air Flow Meters (MAF) used on the Z31: "Adjustable (FED - Yellow Sticker)" and "Not Adjustable (CAL - Blue Sticker)". The differences are explained below.

==== Adjustable (FED - Yellow Sticker) ====

Behind the "Seal Plug" is a variable resistor (potentiometer or POT).
While this is called a “variable” resistor, it actually sets the
constant resistance on wire #31, which sends the MAF signal back to the ECU
(Ra and Rb in diagrams).
You can manually adjust this resistance by removing the plug and turning the resistor, as shown
[here](z31/AFMCalibration.html).

==== Non Adjustable (California Smog Blue Sticker) ====

On the California-spec (blue sticker) MAF, pin #30 at the ECU connects to an Exhaust Gas Temperature (EGT) sensor instead of a variable resistor. This means the “constant resistance” is always changing based on actual EGT. Yellow sticker (federal) MAFs only change if you manually adjust them, while the blue sticker MAFs vary with exhaust temperature. To modify the blue-sticker MAF’s resistance, you would need to physically access the circuit.