Q: I will buy a car in the US, and has the powertrain fault indicator on. Is it cheap to fix it?

YourMechanic can dispatch a certified Mechanic to personally inspect the vehicle in the U.S., in a pre-puchase inspection and e-mail a complete report to you. The report would note the specific Diagnostic Trouble Codes associated with the Powertrain issue that you are referring to and the associated "possible" parts in need of replacement. However, to get a conclusive estimate of the cost to repair the powertrain issue (i.e., your specific question) requires an actual diagnostic such as a check engine light diagnostic. Inasmuch as the vehicle is damaged, such a diagnostic is a little risky in terms of reliability because diagnostics are typically done on otherwise fully functioning vehicles. I recommend you go the inspection route, that is obtain a pre-purchase inspection. Unless the price on the vehicle is unbelievably low (indeed close to its scrap value) buying a collision damaged vehicle remotely, without a comprehensive, authoritative and complete report on its present condition is not wise. If you have additional concerns, questions, and/or wish to schedule a pre-purchase inspection, we are here to help you.