The transient electromagnetic topology (TEMT) method is improved to include random and nonuniform transmission lines first and then is applied for the analysis of a car with complex wiring, which is composed by two random and a nonuniform transmission lines, under an electromagnetic pulse (EMP). In the TEMT method, the SPICE model for the nonuniform transmission line is composed by cascading the SPICE models for the segments of uniform lines, which compose the nonuniform transmission line. For the random transmission line, the average parameters are computed first and then the SPICE model is developed as the usual transmission line. The study on the car with complex wiring show that the improved TEMT method can deal well with the nonuniform and random transmission lines and the induced voltages of the devices generated by the EMP can be up to 100 V, which may cause upsets or damages to the devices.