The Check Engine Light remaining on ways that there is an issue in your car that influences exhaust emissions. Think about the ECM as a sort of computer system, because that's exactly what it is. Just as your home computer's motherboard manages the memory chips, the disk storage space system, the DVD drive, and the video display, your auto's ECM regulates engine parts similarly.
Most of the engine delaying problems will be digital based, while some issues are noticeable such as a loosened connector, others could be challenging to find such as an internally shorted circuitry harness, though rare, it does happen.
This is a very common stopping working part, if you have actually had your wheel speed sensing units transformed and you are still getting the wheel sensing flagship one unit fault codes or you have a non communication mistake after that this ABDOMINAL MUSCLE module is what you need.
The switching transistors for the coil went, as well as some digging round discovered a raft of various ECU's with various part numbers, even in these older Fiestas, depending upon points like the engine type, whether it had air conditioning or otherwise, or even the type of dashboard (i.e. some were basic without rev counters, others had extra dials on them).