In most cars a spanner symbol on the dashboard either means the vehicle is due a service or that the ECU has detected a fault. Adiagnostic tool will provide more details if you have access to one or we would suggest having a diagnostic check performed by a Vauxhall dealer or independent garage to find the cause. You may also find it useful to have a look at the vehicle handbook—or owner's manual—as it used to be called. You will find all sorts of useful information in there.