Process improvement is of high importance and with crucial impact on business and prosperity for software developing companies. The requirements on software are that it needs to be produced faster, cheaper and with higher quality. A recent trend in software development is the use of agile methods. The general idea of more lightweight approaches can also be applied to process improvement. In this paper the authors describe a fault-driven lightweight process improvement approach to be used between projects. The objective is to decrease the number of faults and hence shorten the project lead-time. The fault-driven process improvement approach sets focus on business requirements and relevance for the company associated with this study. This paper discusses the need for a lightweight approach and introduces a lightweight process improvement method. It also reports on some findings from an industrial study and presents some conclusions.