But if the car runs, it's not the RCM. The reason that the fan runs fast due to a bad RCM is this:

If the RCM's engine control relay output fails, then what you get is a powered up Fan Controller (with the key on) and a NOT powered up ECU - cause the Fan Controller is powered directly from the ignition switch, where the ECU is powered up by the RCM's engine control relay output. If the engine runs, the engine control relay output of the RCM has to be OK, otherwise, the engine would not run.

So if the car runs, the engine control relay output of the RCM is good, in such a case, the fast running fan is not caused by the RCM.