My buddy and I just cleaned his computer and we hooked everything back up to where it should be but the monitor goes into a self test I have tried everything that I can think of to fix it but no luck thanks for the replies

Usually the monitor goes into self-test mode when the input loses the signal or if ac power is removed and then restored (e.g. momentary power outage).

Is your computer running when this happens?

Does this happen after computer boots up?

Chck all connections are tight, snug, and fitting properly. Make sure the video card is inserted fully, and any other card(s) you may have.