I have a '98 F150 with 5.4L engine. Because of increasing gas prices, I switched from the performance program (which worked flawlessly) back to stock. Now, I keep getting a check engine light with the following codes: 0171 (sys. too lean - bank 1), 0174 (sys. too lean - bank 2), and 1000 (monitor checks not complete, more driving required). I'll clear the codes to reset the light, but they keep coming back - usually after driving 100 to 200 miles. Engine seems to run fine, gas mileage is normal. This has happened four times now.

Could this be related to changing programs, or something new and separate. Am I hurting the engine by driving it this way?

Thanks,
Jimmy

 

Okay... disconnect the battery for 30 minutes. This will allow the computer to start its adaptive programming from a known state. Make sure the fuel injectors are clean (that can cause a slight lean condition), air filter clean, etc. If the condition persists, check the O2 sensors last.