We present 21-arcsec-resolution CO observations of the spectacular molecular outflow associated with RNO 43. This outflow extends over nearly 5pc and is thus one of the largest known. The high-velocity CO emission is broken up into several distinct regions of high excitation. Each of these regions subtends a small angle at the young stellar object driving the flow, and four show coincident optical emission in the form of Herbig-Haro objects, supporting the hypothesis that the collimated jet responsible for the Herbig-Haro objects also drives the molecular outflow. The jet is episodic and wanders in its direction. We show that the asymmetries in the outflow can be explained by a symmetrical jet propagating in an asymmetrical cloud. The jet has had a considerable heating effect on a large fraction of the volume of its parent molecular cloud.