Originally Posted by Dr Dave
Can some one tell me what this square wave from a Toyota VVT oil control solenoid 4.0 means? I think that since the wiring to the ECM check out I see the ECM not able to pull a solid ground .That would be a ECM internal /transister? or maybe a bad ground to the ECM/?
A square wave will look like the one in your image if your black lead is not making a connection to ground. Since the waveform looks normal when you connect the black lead to the battery negative, check your ground connection at the sensor when connecting there.