Code 51, Prom

Code 51 sets in the event of a faulty PROM unit, if PROM unit is improperly installed (may not set a code if installed backward) or if some PROM pins are not making contact (i.e. bent). Ensure PROM pins are not bent and are inserted properly into ECM. Ensure PROM is installed in proper direction as shown in chart.

CAUTION: It is possible to install a PROM backward. If PROM is installed backward and ignition is turned on, the PROM circuitry will be destroyed and replacement will be necessary. Also see caution under ECM in REMOVAL, OVERHAUL & INSTALLATION article in this section.