All information for 1990 Corvettes provided by BadjerJim on CorvetteForum
Replacing the ERPOM in the ECM
Things you will need:
Note: this procedure and related pics are for 1990-1993 Corvettes. Earlier models had the ECM stashed up under the passenger-side Breadbox. [See 1986 through 1989 procedures]. Later models, you need to ‘flash’ the ECM (or send it to pcmforless.com for an exchange programmed unit).
- 10mm nut driver or socket
- Newly flashed ECM chip with VATS removed – can be purchased from pcmforless.com and also custom tailored to your liking with other performance enhancements at the same time.
Note: this procedure and related pics are for 1990-1993 Corvettes. Earlier models had the ECM stashed up under the passenger-side Breadbox. [See 1986 through 1989 procedures]. Later models, you need to ‘flash’ the ECM (or send it to pcmforless.com for an exchange programmed unit).
- Pop the hood, and locate the ECM. You can’t miss it: the ECM is on the driver’s side, above the battery, as shown in the following pic:
ECM Located under the hood on the driver's side
- Pry off the plastic cover that protects the wiring harness connectors. It kinda has a velcro-like stuff that sticks it to the top of the ECM. When removed, the ECM will look like this:
- Remove the three nuts that secure the ECM. These are 10mm nuts. For the one near the cruise-control gadget (farthest toward the driver’s side of the car) you need a socket extension.
- When the three nuts are removed, carefully turn the ECM upside-down. You do not have to unplug any of the wires on the ECM. This will reveal the cover plate on the ECM, as shown in the following pic:
- Remove the four hex-head screws that secure the cover plate. These are small SAE-size screws (not metric). With the cover removed, you can access the stock programming chip. It’s right under the cover. My chip was blue plastic. Note that there are plastic retaining clips on each end of the chip, as shown in the following pic:
- Fold down the plastic tabs that retain the stock chip. They fold down, out away from the ends of the chip. This will pry the chip up slightly so it’s easy to remove. Then, just pull the stock chip straight up and out of the ECM.
- When dealing with any computer chips, static electricity is an issue. Before you continue, discharge any static electricity you may have on your hands (like… by pulling on a big wool coat). To do this, just pat the plenum on the top of the engine. Say something soothing to your car like: “Good girl… this will all be over in a minute…”
- Connect one side of the old stock chip onto the connectors of the chip-adapter provided by pcmforless.com. Pay attention to the orientation of the stock chip, and where it plugs into the adapter. Complete instructions are provided by pcmforless.com when you buy the chip-upgrade.
- Plug the new pcmforless.com upgrade adapter into the ECM. Push it straight down onto the connector. Fold the two plastic retaining clips back up over the ends of the adapter, so it looks like this:
- Put the cover back on the ECM (4 screws). Flip the ECM over, and put it back into its bracket. Secure the 3 10mm nuts. Replace the plastic cover over the wiring harness.