1999 F-150 Gryphon DCT

[Power Hungry]

As Supercrew indicated, P1131 deals with lack of switching on one of the upstream O2 sensors. This could be a bad O2 sensor, but if there was no prior issue then I'd say it's unlikely.

A more likely cause is actually related to the programmer, but not actually a problem with the programmer itself. When reprogramming the PCM, all the stored data is cleared out including the fuel trims. Until the PCM has a chance to relearn, there is a reasonable chance that you'll set a DTC for either Rich or Lean codes.

Being that it appears that you have a lean condition, my recommendation is to actually get your injection system serviced, or at least purchase a can or two of fuel injection cleaner and start adding it to your tank. More often than not, the injection system starts building up deposits and over time the PCM learns to deal with it. When the PCM get reset, all of a sudden the base fuel values are out of range and the PCM can't learn fast enough in a drive cycle to prevent the DTC from being set. Cleaning the fuel injection system will help eliminate those deposits and allow the injector flow to more accurately match the base calibration in the PCM.

Unless you reprogram your PCM again, you shouldn't have any further problem. If you do change levels, you can probably expect the code to appear again 1 or 2 times and then go away.

Hope this helps.