A fluid injection module may include a fluid ejection die, a die carrier, a bypass fluid passage in at least one pressure regulator. The fluid ejection die may include nozzle orifices on a front face of the die, first and second fluid passages extending through the die and a microchannel extending from the first fluid passage to the second fluid passage proximate the nozzle orifices to circulate fluid from the first fluid passage to the second fluid passage. Third and fourth fluid passages may extend through the die carrier. The bypass fluid passage may extend from the third fluid passage to the fourth fluid passage while being connected to the first fluid passage and the second fluid passage. The at least one pressure regulator is to induce pressure differential driven fluid flow across the microchannel and across the bypass fluid passage.