The 443 code is a monitor detected failure for either a short or an open to the purge valve.
If you take the PCM connection off you won't read any voltage which would be normal.
Place a shunt (short) on the PCM connector terminals (not the PCM) and measure for that shunt at the purge terminal end with an ohm meter function.
If you see it, the circuit is good in that respect.
Remove the shunt and it clears at the purge end, the circuit is complete.
That leaves the purge valve or it's connector or even a shunt to ground from the positive side.
Check each side of the circuit to chassis ground.
The ground side should read near zero ohms a short, the hot side should read open if the circuit is good.
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The PCM reads the circuit condition by internally checking the voltage drop across a resistance. The value read is the monitor function.
A large voltage drop indicates a short or to much current flowing.
No drop indicates an open. This how the PCM knows what the condition is.
This is about all there is to the general operation for this circuit check.
The issue has to be detected on one of these checks or your missing it.
Good luck.