Before you consider replacing your car's entire ECM, you should ideally test it first to make sure that it can't be repaired or fixed. There are numerous ways to test and diagnose an ECM to ensure that it's working properly (or not). First off, you should try to see if there are any physical defects on or around the ECM. Mainly, you'll have to check the wiring to see if there's any corrosion, burns, fraying, or loose connectors. If you can crack the ECM housing open, you should also take a peek to see if the ECM's circuit boards have fried. Alternatively, give the ECM a smell to see if you can spot a burnt scent - this is indicative that the board has fried. Then, inspect the ECM's pins, plugs, connectors, and so on within the ECM unit to ensure that there's no corrosion, burning, or damage.