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Programmable Read-Only Memory (Prom): Installation

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Vandura Special, 1994 GMC Vandura, 1994 GMC Rally Camper Special, 1994 GMC Rally, and 1994 GMC Forward Control. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ensure new PROM has same service number as old one. Place NEW PROM in PROM carrier, and position squarely over PCM PROM socket. Press on PROM carrier until PROM is firmly seated in PCM.
    NOTE: Ensure reference notches in PCM and PROM are properly aligned. If PROM is installed backwards and ignition is turned on, PROM will be destroyed.
  2. Install PROM access cover on PCM. Install PCM in vehicle. See INSTALLATION under CONTROL UNIT . Start engine, and ground DLC terminal "B". Watch for trouble Code 51 or 52.
  3. If this occurs, PROM is not fully seated in PCM, installed backwards, has bent pins, or is defective. If bent pins are cracked while straightening, replace PROM. If PROM is installed backwards or is defective, replace PROM.
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