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).
  NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

1. Always check to see that the PROM pins are not bent and that they are properly inserted into the ECM.
2. Make sure the PROM is installed in the proper direction as shown in the chart.
3. Check that all pins are fully inserted into the socket. If OK, replace the PROM and recheck. If problem still is not corrected, replace the ECM.

Fig 1: Code 51 PROM

Small notch of carrier should be aligned with small notch in socket. Press on PROM carrier until it is firmly seated in the socket. Do not press on PROM; only the carrier.