Abstract: Examples of techniques for fault diagnosis for fault tolerant chassis architecture systems are disclosed. In one example implementation according to aspects of the present disclosure, a computer-implemented method includes receiving, by a processing device, a control variable for the system. The method further includes receiving, by the processing device, a measured variable for the system. The method further includes calculating, by the processing device, a residual based at least in part on the control variable and the measured variable. The method further includes performing, by the processing device, a fault diagnosis to detect a fault in the system based at least in part on the residual.