Suzuki: 1998 Suzuki Swift service engine soon light, powertrain control module, malfunction indicator light

Question
I was driving home and the "service engine soon" light came on.  What are the possible causes?  What do I need to do?

Answer
You will need to hook up a scan tool and find out what caused the "MIL"(malfunction indicator light) to illuminate, and determine if it was a one time "glitch" of no importance, or a defect in a signal/input/output from the "computer", or ECM(engine control module) or "PTM"(powertrain control module).
It's worth pursuing, because without the proper functioning of all the devices, performance, fuel economy, and possibly engine longevity can be compromised, in addition, it could lead to terminal dandruff, halitosis, and flatulence.