Code 51 - Prom Error Indicator: Notes

If code 51 is a hard failure, it will be displayed continuously until diagnostic mode is exited. If code 51 is an intermittent failure, it will be displayed only in the first 2 passes of diagnostic display. Code 51 indicates that the calibration PROMS are not being read properly by the ECM.

PROMS installed backwards or PROMS installed with missing or bent pins may cause this code to set. Remove PROM cover on ECM and verify that PROMS are installed correctly.

If the PROMS appear to be installed correctly, turn the ignition off for 10 seconds and then check if code 51 remains. If so, replace PROMS. Turn ignition off for 10 seconds and check for code 51. If code remains after replacing PROMS, replace ECM.