Enhanced Auxiliary Power Control Modules (APCM) are critical pieces of controlling equipment that body manufacturers are using with the Ford 7.3L Diesel Power Stroke. They're simple to set, easy for the end-user to use, and they accomplish the critical task at hand.
However, if this inexpensive device malfunctions, damage due to overspeed conditions may occur to the PTO or the auxiliary equipment it powers. Ford's APCM will limit the rpm to 2,500, even though the APCM may show 4,100 rpm.
Remember, the engine speed determines the operational speed of the PTO. Using the formula:
Engine speed = Max PTO speed ÷ PTO ratio
Review the maximum PTO operational speed designed for use with the 4R100-ZF transmission carefully. Note that Chelsea and Muncie, which both offer PTO kits to fit this transmission, have different operational speed preferences.
The affected vehicles are Super Duty F-series with the Enhanced APCM, part number XC3F-12B640-AA, included in kit part number XC3F-12B641-AB. On order or pool units, the part may be installed as LPO: Auxiliary Idle Control Kit, Option Code 96P (Code 961 for Econoline). Specialized Limited Function APCM or Ambulance APCM will not be affected.
Ford's Product Development Center issued an advisory letter (Jan 3, 2002), which followed the Special Service Message (SSM) #15450 that went to Ford dealers. Ford also recommends that final-stage manufacturers tell their customers to visit a Ford dealer if they experience the intermittent invalid APCM display readout of 4,100 rpm, and also to refer the service writer to SSM #15450.
Ford's Powertrain Control Systems Division offers the operating instructions for the Auxiliary Idle Control Module, which should be followed for installation and operation of all APCMs (part number XC3F-12B639-CA).
The manual provides all relative codes for installation and correction of the APCM unit.