GM OBD Trouble Code 51

Incorrect MEM-CAL / PROM Error

The PROM and the MEM-CAL basically serve the same function. The PROM was used in earlier model years and the MEM-CAL was used in later model years.

If the ECM detects an internal fault with the PROM or the incorrect MEM-CAl is installed, code 51 will set. The PROM/MEM-CAL is a special "chip" that is installed in the ECM, based on the particular vehicle configuration.

Fault Code Description

  • 51 - PROM/Incorrect MEM-CAL


  • Engine may not start
  • Poor engine performance

Common Problems

  • Internal fault with PROM / MEM-CAL
  • PROM or MEM-CAL incorrectly installed in ECM

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