What are these ECU Codes I keep hearing?

Hello all. I keep hearing about checking the ECU Codes. Can someone shed some more light on this please. I am still having a problem starting my car even after I resoldered the Main Relay. I am desperate now. I was thinking I could investigate further if I knew how to read the ECU Codes.

One more thing. When I turn my switch to the on position I can hear the fuel pump come on and off. I have heard this rules out a main relay problem. Is this true? If it is not then maybe the resoldering didn't fix my relay and it is still at fault.

Thanks in Advance!

Well I can answer your first question. The ECU is your cars computer that does all the calculations and monitors everything. When a problem occurs, typically something alerts the ECU that there is a problem. Depending on how the ECU located the problem/assumed source of the problem, the ECU assigns a certain code number to it. When this happens, the ECU logs this code. With the proper electronics(Autozone does it for free) they can tap into some wiring near the front floor of the passenger seat and retrieve these numbered codes. Each of these codes stands for something, so when retrieved they can help diagnose the problem you are having. Use the search feature in this forum(up at the top right of your screen) to find other posts with instructions to get codes from the ECU on your own. Good luck

Thank you very much, Igovert500. But I had my car towed awa;y today because I could not figure out the problem. My original problem was my car suddenly died on me like someone just took out the key. I have always had problems with starting it in the hot sun. I resoldered my main relay, underneath the dash. Still the same problem: Would turn over but never spark. Make a long story short: The repair shop says it is my distributor. 400$$

Thanks Man anyway for replying. Take care.