how to read the diagnostics tool on y reg vectra?

i have a 2.2 y reg vectra LS petrol i have the ecu light on my dash lit i need to diagnose the fault and have got myself a dianostic tool its a simple tool made by haynes/draper it basicly bridges the connection of selected pins its says use pin 4 and 6 in the ecu diag plug located under the dash (imbetween the handbrake and gear lever under the flap)i have done this and it says there will be a sequence of flashes to indicate the code i do not know where to look for these flashes i looked on my dash and there was no flashes or pulses am i doin any thing wrong please help