Discussions

This was started in a different forum but it does fit into this one, so I have reposted it here. The question was about the "check engine light" or "service engine light soon". The check engine light is letting the driver know there is a malfunction with engine management system. Usually something causing the emmissions to exceed government regulations. The light is to tell the driver he/she should have it serviced because of a malfunction in a engine management system or a sub system, it usually has nothing to do with the engine mechanically. A shop will put a scan tool on the vehicle to retrieve a DTC (diagnostic trouble code). If it is a vehicle 96 and up it will be a letter and then numbers (eg. P0174). This code is a starting point for the technician. The service manual will give the definition of the code, what system it affects and test to be performed to pinpoint the problem. This light can go on and off depending on what kind of fault is being set. I can be on all the time or flashing. It can stay on for days and then magically go out(this means the computer has set a code and after a certain numer of engine starts without seeing the fault again it will shut it off).