Code 51 - Faulty Prom

Code 51 sets if any of the following occur:

Faulty PROM unit.
PROM unit improperly installed (may not set a code if installed backward).
Some PROM pins 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 backwards. If PROM is installed backward and ignition is turned on, the PROM circuitry will be destroyed and replacement will be necessary.

Fig 1: Code 51 - PROM Replacement Use associated text with Flow Chart.