OBD2 and Torque

When my 2004 Jeep Grand Cherokee's check engine light came on last week, I invested $24 for a Bluetooth OBD2 scan tool from BAFX and installed the free (I love free) Torque app on my Android smart-phone to diagnose cause.  Then I made sure the gas cap was tightly sealed. Case closed.

http://www.amazon.com/gp/product/B005NLQAHS

http://www.obd-codes.com/