Worcester Bosch Boiler EA fault?

I have read all the answers about frozen condensate pipes but it has not been freezing here and the pipe actually seems to be empty of liquid but there appears a residue of green goop. Should it have some liquid in it? The pipe I am looking at runs from something that looks like a pump through the back of the boiler into a more sturdy pipe, then through the wall onto an external pipe that then runs to a drain. The pipe from the boiler is clear and about 5-10mm in diameter. Any ideas please? Boiler seems to work when it wants to then gurgles in a deep resounding belch then the light goes out and the EA fault is diaplayed. Upon relight it lasts about 1 minute then locks out again.