How do you reset brake pad warning light on vectra c?

The type of sensor used is sacrificial in design and must be replaced once the pad wear indicator has been activated on the relevant wheel. When replacing the pads, disconnect the sensors one at a time, front and rear, and test for continuity (complete circuit) with a multimeter or test lamp and 12volt power source. The faulty sensor, which will in normal circumstances will be the front left one, will not reveal a complete circuit and you have now located the "fault". Replacements may be ordered from your dealer.

Alternatively, to "reset" or clear the displayed fault from your dash, you have only to complete the circuit of the sensor cable! No resistors are required to be fitted to achieve this.

It should be further noted that pads and discs should be replaced at the same time as they are designed to wear together, replacing the discs does not entail fitting new wheel bearings as the discs mount directly to a spindle hub and are retained by one countersunk screw until the wheels are refitted, machining of the discs is not recommended.