engine management light

[victorM]

as above the e/m/light comes on intermittently without any noticable failure of performance etc, however if its come on there must be a fault somewhere, so without taking the motor to the rip off guys, which type of code reader would i need to buy to highlight the fault so i can rectify the fault?
the motor is an `o2 vectra c 1.8 manual petrol, oh and sometimes the rev counter/speedo and dash lights fail but come back within seconds i`ve dissconected the abs switch for 10/15 mins but to no avail, problem still shows. any helpers please?

[Ademusic]

Wouldn't it be cheaper to just have the code read rather than buy a reader to do it youself?