Glow plug resistance measurement circuit and method

A method for measuring the resistance RGP of a glow plug 360 comprises (a) connecting at least one resistor 510, 550 of known resistance RSH Rref to the glow plug to create a voltage divider 600 between a feeding node 535 and a ground node 365, an intermediate node 515, 520 being provided between the glow plug 360 and the at least one resistor (510, 550); (b) integrating over time alternatively a first, a second and a third voltage signal VI, V2, V3 as input signal VINT,in to obtain an output signal VINT,out (c) comparing the output signal VINT,out with a low threshold value VL and a high threshold VH for generating a pulse width modulated signal VPWM (d) selecting the voltage signals VI, V2, V3 as input signal VINT,in in step (b), on the basis of a variation over time of the pulse width modulated signal VPWM and (e) determining the resistance value RGP of the glow plug on the basis of the known resistance value RSH Rref and of a variation over time of the pulse width modulated signal VPWM.