1. Service Manual Terios 2004 1-5

This is typically telling you that the pollution control system thinks there may be a problem. There are oxygen sensors and Engine coolant temperature sensors that tell the computer what air/fuel mixture to use.

Service Manual Terios 2004 1-5

If the computer does not like the information that it is getting, it turns on the light, and stores a fault code that a mechanic can access. If the light is on steady, it's usually not a big deal. If the light is flashing, there could be a serious problem. Time to talk to a service center. Answered on Mar 27, 2016.