DTC 51

Code 51 PROM Error Indicator

If Code 51 is a hard failure, it will be displayed continuously until the diagnostic mode is exited. If Code 51 is an intermittent it will be displayed 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 their pins bent or missing may cause this code to set. Remove the trap door on the ECM and verify that the calibration PROMs are installed properly.

If the PROMs appear to be installed properly, turn the ignition off for 10 seconds and then check if Code 51 remains. If it does remain, replace the PROMs. Again turn the ignition off for 10 seconds and check for code 51. If the code remains after replacing the PROMs, replace the ECM.