A control method and apparatus for a diesel fluid injector located in an exhaust pipe of a diesel internal combustion engine. The method comprises: energizing a solenoid of the injector to perform a diesel exhaust fluid injection; determining a voltage value (Vcoil) indicative of a voltage applied to the solenoid; determining an electric current (Icoil) value indicative of a current flowing through the solenoid; calculating an electric resistance (Rcoil) of the solenoid as a function of the voltage and current; and estimating an injector temperature (Tcoil) value as a function of the resistance. Preferably the diesel fluid injector is a urea injector upstream of a selective catalytic reduction (SCR) device. The current value may correspond to a maximum or average current flowing through the solenoid. Methods of refining the injector temperature estimate include using parameters such as the exhaust gas temperature, a fuel quantity value, an ambient air temperature, and an ambient air pressure.
