My sister was recently driving my ranger, when she called and said the check engine light came on. She immediately went to an Autozone and it was determined that my oil was pretty low. (I have no Idea I check pretty often) Now after more oil was put in, the engine runs beautifully, but the check engine light is still on. Does anyone know what could be the cause of this? 2001 XLT 3.0 V6

 

Take your pick: OBD II trouble codes | Ranger Forum - Ford Truck Fans

You really need to get the code or codes from the computer, computer turns on CEL when it has stored a "trouble" code in memory.
A few thousand choices if you want to guess :)

CEL on means "heads up something doesn't add up, check it out when you get a chance"

Flashing CEL means "CHECK IT RIGHT F*ING NOW!!!"