Could be a failure in one of the following:

Head gasket - usually accompanied by water loss - it's the water in the fuel
mixture that causes the pinking

Intake gasket - allowing additional air in, resulting in weak mixture on one
or more cylinders - and you might get rough idling and hesitation on pickup.

Any one of a number of electronic sensors - as Gary said, the timing is
totally controlled by the computer - the computer decides where to set the
timing dependent on several inputs; engine speed, load, exhaust analysis,
atmospheric conditions etc., and ultimately two or more knock sensors. These
are located on the engine block and physically detect any pinking (or
knocking). If pinking is detected, the computer retards the timing until it
stops. If a knock sensor isn't sensing, the computer doesn't know to retard
the spark and you hear the pinking. An OBD readout should pick up a failure
any of the sensors.

Good luck !