DTC 51

Code 51 - PROM Error (Faulty Or Incorrect CAL-PAK):

CAUTION: To prevent possible electrostatic discharge damage to the PROM, do not touch the component leads or remove PROM from carrier.

CHECK PROM

1. Check that all PROM pins are fully inserted in socket.
2. If okay, replace PROM, clear codes and recheck.
3. If code 51 reappears, replace ECM.
4. Clear codes, confirm "Closed Loop" operation and no "Check Engine" light.