Pull-Down Hall Effect Sensor

When this type of sensor is not in it's pulled-down state (i.e. not triggered), is the 5V that is found on the signal wire sourced from the sensor's 5V voltage supply wire?

It is sourced from the PCM. The Sensor will Pull-Down this voltage when it is triggered.

Quick check, Key ON, sensor unplugged, there should be 5 volts present on the signal, or there is a problem, open, short, pin fitment or PCM.

A pull-up sensor is sourced from the 5v ref, so when this sensor is triggered it pulls the signal wire up to the reference voltage.

I hope this helps.

Thank you and, yes, the explanation helps a lot!

I was watching several YT repair vids where sensor bypass tests were being performed- that is, ground was applied via a jumper to the sensor signal wire- and I wasn't sure if the sensor needed to be plugged in so it could provide the steady 5V or if the voltage was sourced from somewhere else.

Just 1 more question, if you don't mind: With a pull-up sensor setup, instead of supplying 5V like in the pull-down design, does the PCM apply ground to the signal wire instead?

 

 that is, ground was applied via a jumper to the sensor signal wire- and I wasn't sure if the sensor needed to be plugged in
 

This "by-passing" is done on three wire sensors ( ie. Crank or CAM Position) to set either Circuit High/or Low codes.  This is often done to prove circuit integrity and that the PCM is doing its job and the said part is bad.  By-pass testing is performed (usually) with the circuit unplugged to isolate the sensor.  Depending on sensor design, Pull-up, or Pull-Down you can ground the signal and pull it down like a pull-down sensor would OR jump the 5v reference the signal to pull-up the signal like a pull-up sensor would do.

With a pull-up sensor setup, instead of supplying 5V like in the pull-down design, does the PCM apply ground to the signal wire instead?

The PCM continually supplies a ground to a three wire sensor, the sensor when triggered pulls-up the voltage on the signal or it allows the 5 volt reference voltage a path to the signal wire.  With this sensor design there will be "Zero" volts on the signal unplugged.

This is why it is very important to do the "unplug-it" test to verify the voltage level on the signal wire.

Signup for SD Premium, Paul Danner has an awesome 4 or 5 part series on Signal Circuit integrity.  This is a MUST watch.