[Richard L]

Thanks for the wealth of information on the last two posts. With your help, I can learn to retrieve theinjector signal much quicker.

There are two types of piezo injector based system. If you have help me identify them first, we can go deeper.

1. High pressure common rail, piezo injector acts like a normal solenoid valve.
2. Low Pressure fuel is fed into the piezo injector at about 40psi. When the multi-staggered piezo element is energised, push iong the fuel into the combustion at a very high pressure.

The piezo injector are fired using a switch-mode power supply, generating a rail voltage of around 300-400 volts. Power is fed to the Piezo element is in a semi-resonant state during firing. Piezo electric behave more like a capacitor/inductor than a resistor.

Is the Controller is made by siemens/VDO?

You are correct that the piezo injector is switched on both rails. It is more involved than altering the +/- PWM mode. Lets try "PWM(-)", wire to the -ve side the injector and let me know if you see an sign of detection on the green led. (I am referring onto the green wire of the yellow harness). The blocking diode on the HFS-6 is good for 600Volts.