This might help. Let us know what you find!
P1335 - Exhaust Gas Recirculation (EGR) Position Sensor Minimum/Maximum Stop Performance
Description: This DTC is set when the voltage of the EGR valve position sensor greater than the bottom limit threshold.
Possible Causes: Carbon buildup on EGR valve due to insufficient clean fuel, low fuel pressure, insufficient engine cooling, excessive oil in the intake air system or incorrect module calibration level.
Diagnostic Aids: This DTC is set when the powertrain control module (PCM) detects the EGR position sensor voltage is greater than 1.5 volts for greater than 2.5 seconds when the EGR valve is not being commanded by the PCM. Check the EGR valve for any carbon that could be holding the EGR valve open.
'05 F150 5.4L FX4 SCrew
'10 F350 6.4L Lariat FX4 CC SRW LWB