HOWTO Socket The PCM

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This tutorial shows the steps on opening the PCM and replacing the PROM with an EEPROM, thus allowing re-programming of the stock computer.

Tools / Materials

  • PCM
  • 7mm Socket with driver
  • T-15 (Torx) Attachment
  • 29C256 EEPROM (No longer available) (You want one with a 90ns time or lower) or a 29C256 Emulator (Such as AutoPROM)
  • 27SF512 chip (It is a 512KB chip, you just write to the last half and it will work fine)
  • 28pin ZIF Socket (Highly recommended, but not really required. I used one from Moates


Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
  1. Remove PCM from vehicle and set on a work area. Be sure to destaticize yourself by touching something metal and that is preferably grounded.
  2. Remove the six screws as indicated in Figure 1. The three screws on the heatsink can stay in the PCM. The number highlighted in red is the part number, which can be looked up at PCM Identification. I encourage you to add yours if it is not already on there.
  3. Slide off the top cover and remove the two screws as indicated in Figure 2. Underneath will be either transmission board if you have an Automatic PCM, or just the ECM board if a manual.
  4. Push up on the plugs to push the board out of the bottom case as shown in Figure 3
  5. Flip the board upside down and remove the two screws in the corner of the board as shown in Figure 4.
  6. Remove the metal bracket from the PCM (if equipped, I do not know if this is on the manual boards)
  7. Using desoldering braid(what i used), or a solder sucker, remove the solder from the pins as highlighted in Figure 4
  8. Flip the board over and remove the PROM chip as shown in Figure 5. Do not force this out if one of the pins is sticking, just heat it up or remove any solder if necessary.
  9. Put the ZIF socket in with the handle facing away from the transmission board cable (if equipped) so that it does not collide with anything between the opening and closing motion.
  10. Solder the ZIF socket in place using the pins as shown in Figure 4. Look closely at all your connections, be sure you have no cold solder joints.
  11. Put the PROM chip you removed (or EEPROM if you have already programmed it) into the ZIF Socket. Be sure the cutout (Number 1 pin) is facing toward the outside of the board (Down in Figure 5)
  12. Re-assembly is reverse of disassembly.
  13. Test drive your PCM, be sure there are no codes (you'll know immediately if there are, code 51 will come up and your auto transmission will drive only in 2nd gear).