On 4 Sep, 1943, U-228 was ready to sail for a war patrol in the North Atlantic, but her sailing was suspended until the new Wanze radar detector was available due to the recent U-boat losses in the Bay of Biscay. The boat was then transferred to Brest to take four of the new Gnat torpedoes aboard, but the sailing was then further delayed because the radar detector did not work satisfactorily.

On 27 September, U-228 eventually sailed together with U-413 escorted by five minesweepers but both U-boats had to return to port after carrying out a deep dive trial. Some valves of U-228 leaked and the listening gear was unable to pick up the noises of the nearby escort ships. This boat and its sister U-229 were the first U-boat equipped with a listening gear that used magnetostriction receivers and the technicians of the shipyard had troubles discovering the cause of the problem. On 9 October, the gear worked during trials in the roads and U-228 sailed for patrol two days later, but again the listening gear didn’t work during the deep dive trial and forced her to return to port yet again. It was discovered that the new receivers became deaf after diving deeper than 100 meters. This was fixed and U-228 finally left for her third patrol on 23 October.