Ok so its been almost a year with no DPF and the only code I keep getting is P041D.

The code only goes on in above #2000 feet sea level. Every trip I take up into the mtns the code comes on.

How can I fix this?

Other problems is my 4x4 light on my dash will not come on. How ever the 4x4 light works on the knob.

Any help would be great thanks