Check engine on with code p0171. the code has been on for over 6 months without any cause/reason. i have worked with lexus and followed recommendations from lexus without any success of resolving it. lexus took a fuel sample in august 2010 and i have not received any responses from lexus as of nov. 15, 2010. since the "check engine" light has been on regardless since feb. 20, 2010, the function of "check engine" light is lost. this is a safety hazard as the driver will no longer receive any warning of any real potential problem with the vehicle. updated 01/20/11 *bf the consumer was informed the oxygen sensor needed to replaced. however, the check engine light illuminated again. the dealer has been unable to pinpoint the problem.