It could be a nubmer of reasons, you may need to get a code tester to see what codes may be showing up to determine why the light comes on. Most likely a bad sensor?
197000 miles does Possibly, and most likely, the oxygen sensor.
service engion soon light is on
That is one of many possible causes.
well it needs to be serviced...soon
The service engine light is the same thing as a check engine light.
The service engine soon light comes on when the engine computer has detected a malfunction and set a code. You need to have the system checked for codes to know possible causes.
There are pages and pages and items that can cause a check engine light. You need to have it checked for codes with a scan tool.
Get the computer scanned to see what the problem is.
the computer tells it to glow.
If the check engine/service engine light is on, the problem most likely isn't in the ECM. Get it fixed, and it should go off.
There are many causes for a service engine light. You need to have it checked for codes. Then you can diagnose from there.
The service engine soon light comes on when the computer detects a malfunction and sets a code. see related questions below for more info.