Control system for construction machines

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 11 of manufacturer 10 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 D1, D2, D3 collected. The server unit 11 of the manufacturer 10 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.