The German champions lost the first leg of their quarter-final 3-1 in Porto but won the home leg 6-1.
And Bayern boss Pep Guardiola, who used to manage Barca, said: “The only way we can make the final is by playing better than Barcelona and doing what we did in the second half [of the first leg].
“Our only desire is try until the end.”
The German champions are without wingers Franck Ribery and Arjen Robben, who are both out for the season, while Barcelona are at full strength.
As well as missing key men Ribery and Robben, Bayern defender Holger Badstuber and left-back David Alaba are also currently sidelined.
Including a penalty shootout Bayern have lost four games in a row, while Barcelona have won their last eight, keeping seven consecutive clean sheets.
Guardiola rested four first-choice players on Saturday against Augsburg, keeper Manuel Neuer, midfielders Xabi Alonso and defenders Mehdi Benatia and Rafinha. However they lost 1-0 and Neuer played most of the game following Pepe Reina’s early red card.
Barca rested five players including Andres Iniesta, Jordi Alba and Sergio Busquets but beat Real Sociedad 2-0 to boost their title hopes.
Guardiola said: “We are the Bundesliga champions and we’ve had an extraordinary year, despite some difficulties.
“I’ve never had to solve everything based on courage alone nor have I ever told my players that we will have to be braver than our rivals.
“We have to be more aware of what our offensive duties are and, after the game, the result will speak for itself.”
Bayern retain belief they can pull off one of football’s great comebacks and forward Thomas Muller says “we all know it’s a mammoth task, but we haven’t given up on it”.
Striker Robert Lewandowski added: “We have to give everything we’ve got. We’ve shown often enough what we’re capable of here in Munich. It’s not over yet and we’ll battle to the end.”
Barcelona are chasing a club-record 48th win of the season in all competitions.
Defender Marc Bartra said the Catalan side’s aim was “to go to Munich to win” but he is wary of Bayern’s quarter-final comeback against Porto.
“We know it will not be easy, because we saw what happened there to Porto, so we need to go out and have a big game,” he said.