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).
Always check to see that the PROM pins are not bent and inserted properly into ECM. Make sure the PROM is installed in the proper direction as shown in the chart.