After cleaning the throttle, the engine fault light appears and disappears from time to time.

First of all, according to the situation you described, if the engine fault light comes on only because you forgot to connect the plug after cleaning the throttle, then you just need to clear the relevant fault code directly. Simply put, you can try to disconnect the negative terminal of the battery, but if it is convenient, I suggest you go to the nearest 4S shop, use the fault detector to detect the engine control system through the computer, find out the specific fault, and then check it according to the actual situation or directly remove it with the fault detector.