Control system for construction machines

1. Field of the Invention Abnormality can be judged accurately by considering information other than a sensor-detected value. Determination of an abnormality degree, namely an urgency degree, is enabled, and an abnormality can be processed accurately according to the determined result. Only information really useful is given to the side of an administrator, and the communications cost is suppressed. Server unit of manufacturer judges the abnormality degree of a construction machine on the basis of a combination of all or two of first to third construction machine information D, D, Dcollected. The server unit of the manufacturer ranks the abnormality degree of the construction machine in respective levels of Rank 1 (Normal), Rank 2 (Warning), Rank 3 (Abnormal) and Rank 4 (Emergency) on the basis of the number of occurred times of error codes collected for the unit time.