Originally Posted by txgreasemonkey
The biggest cause of ECMs (computers) being damaged is from flooding. The second leading cause is from water damage in the summer, when windows are left down, and it rains. See if you think your ECM could be experiencing water-related damage. If so, do extensive price comparison shoping, and replace it. O'Reilly Auto Parts sells remanufactured ECMs, with a lifetime warranty. Check out what works best for you. They are not difficult to replace.
The ECM is a giant circuit board inside, with capacitors, resistors, and microprocessors. It's easy to see how water damage could short out and damage this critical item. On OBD-I systems (before 1996), such as yours, ECMs can throw codes and tell you when some other component is failing, but they do not have to throw a code and tell you they are failing. If your Check Engine Light comes on and stays on, and no codes are thrown, it's a real danger signal the ECM may be bad. A smart diagnostician can test the voltage the ECM is providing key sensors and tell if it is likely the culprit. ECMs are "power transistors," whose prime job is to provide the proper voltages to a host of sensors, under constantly varying conditions. Hopefully, this will give up a slightly better understading of their role and how they can be tested; however, many mechanics might not have this expertise. Therefore, it might be somewhat of a "gut" call by you.
