P Channel Mosfet not switching at higher voltage.

[Gyro]

As I mentioned previously, in the OP's intended application, he can't afford the gate voltage to go to zero. There needs to be a protective resistor in series with the collector of Q1/Q2 to limit the spike currents from the 12V supply, through the gate protection Zener (to be added), and gate capacitance.

This means that the mosfet gate is always going to have to be driven by a resistive divider - the only remaining argument is the resistor values.

[IDEngineer]

I got the impression the OP was a bit flexible as to component selection, at least with respect to the gate transistor. That would permit more optimized gate voltage range and thus minimized dissipation in the PFET. His choice.

[Gyro]

Regardless, he's not going to find a mosfet with greater than +/-20V Gate-Source breakdown. For his automotive application, he's going to need that Gate-Source protection Zener, so you can't just connect the gate directly to the driver transistor collector - you must limit the otherwise high energy current spikes with a resistor in between, otherwise the Zener will just shunt all of the spikes straight into the driver transistor. With the needed Gate-Source resistor too, you inevitably end up with a voltage divider driving the Gate.

[IDEngineer]

 Almost everything I do at the moment is for some automotive application. Our solution is to protect the +12V rail itself. Then you don't have to duplicate individual protection components everywhere such as the gate in question. I guess if you're willing to expose everything else to raw automotive power then what you're describing for the gate circuit is fine. Personally, I seek to swing the gate to the rails for the reasons I stated earlier, and in a properly conditioned 12V system a gate with +/-20V rating works well and reliably.

[Mechatrommer]

rechecking again... both bad as both p-fet in reversed polarity, i'm not expert as to what will happen this way but i'm certain body diode will either burn or in always forward conduction (turned on) the other point is valid...

[MarkF]

rechecking again... both bad as both p-fet in reversed polarity, i'm not expert as to what will happen this way but i'm certain body diode will either burn or in always forward conduction (turned on) the other point is valid...

Good catch.
I had to redraw the schematics and forgot to flip the MOSFETs.
(Post corrected)