I am working on a project where I want to fake the presence of a solenoid valve in a control unit on a car so that the control unit does not give an error message.
The output of the control unit is a 12V PWM signal with about 2 kHz. I measured the solenoid valve with an LCR meter and found a resistance of 5 ohms and an inductance of 10 mH.
I now want to simulate this solenoid valve with a simple coil. Since there are no coils with the exact inductance and DC resistance, I will use a 10 mH coil with 0.5 ohm resistance and a 4.5 ohm resistor in series.
Since I don't have any information on the ECU circuitry, I'm assuming I need a flyback diode for my inductor. Now I am not quite sure where to place it. Parallel to the coil with 0.5 ohm or parallel to the series connection of coil and resistor with 5 ohm?
The aim is that the control unit does not notice that the solenoid valve has been replaced by my coil.
I would be grateful if someone could give me an answer and a short explanation. The control unit costs 2,000€ from the manufacturer... I would be happy if it didn't go up in smoke as soon as I switched it on.