It's all done digitally with the proper access codes and input data.įollowing the Geo Storm, GM began phasing in PCMs with flash reprogrammable chips in a variety of cars and trucks.ġ995, most GM models had the flash reprogrammable PCMs. PCMs built with EEPROM chips can be reprogrammed in a matter of minutes without having to remove the PCM or replace a single chip.
#ECU FLASH TOOL MANUAL#
The General Motors PROM Identification manual that OTC used to provide with their Monitor scan tool and Pathfinder software contained over 362 pages of GM PROM numbers!Įnter the flash reprogrammable EEPROM (Electronically Erasable Program Read Only Memory) chip. We're talking thousands of different PROMS. Every field fix or recall for an emissions or driveability problem created more part numbers to keep track of. Performance enthusiasts also liked replaceable PROMs because the chip could be replaced with one that provided more spark advance, fuel enrichment, a higher rev limit, etc., to squeeze more power out of the engine.īut replaceable PROMS had a serious drawback: there were too many of them! Every model year and every running change meant another PROM had to be created. It also meant that if a bug was later discovered in the original factory programming, it could be corrected in the field by simply replacing the original PROM with an updated corrected PROM (a tactic GM has successfully used over the years to fix many factory flaws). GM pioneered the replaceable PROM chip as a way of programming a limited number of basic PCMs to fit a wide range of GM makes and models.Ī replaceable PROM chip also meant the PCM could be "retuned" if necessary to correct certain kinds of emission or driveability problems. Up to this point, Program Read Only Memory (PROM) chips held all of the PCMs vital calibration information and operating instructions.
GM knew OBD II was coming and that it would require a new generation of PCMs that were faster, more capable and able to be programmed electronically. The choice probably had more to do with production scheduling and new model introductions than profile or image. You'd think GM would have chosen a more high profile vehicle like a Cadillac or Corvette to usher in the new technology. Why a humdrum car like the Storm would be the first to receive a flash reprogrammable computer system is unknown.
Would you believe flash reprogrammable PCMs have been in vehicles for over a decade? The first such application was the 1990 Geo Storm.