How to Tune a Chevy PCM

by David Marsh

A Chevy powertrain control module controls the settings for shift points, cooling fan routines and engine idle and timing. It is an on-board computer that is preset at the factory for average driving conditions in a car or truck that hasn't been modified. If the owner installs a set of headers or a new carburetor, the PCM won't cover it and performance will not be what it should be. The PCM can be reprogrammed with new settings that will optimize performance.

Get the new settings from the website of the company that made the aftermarket additions. PCMs can be reprogrammed in segments. If you have added a new carburetor, you can update the PCM without disturbing the settings for the new set of headers. The programmer will come with a universal serial port that allows the settings to be transferred from the computer to the programmer.

Turn the key off in the car.

Plug the programmer into the PCM port. In most Chevrolets, the PCM port is located to the left of the fuse box, under the dashboard and to the left of the steering wheel. Check your owner's manual or the Internet for the location of your particular model.

Turn the key on. The programmer will scan the PCM and ask for the vehicle's identification number. It may also ask for the engine type and size, fuel system type, speedometer reading and transmission type.

Choose the portion of the PCM that is being updated. The programmer will give you a menu.

Start the information transfer. Depending on the type of programmer you have, you may have to press "Start" or an up arrow. You will see a blue progress bar. It may take up to five minutes to complete the entire transfer.

Turn the key off when the process is complete. The programmer may have further instructions if the PCM has to be recalibrated.


  • close If the programming process is interrupted, the PCM may have to be reset to the factory defaults and the process started again. Always do re-programming with a fully charged battery. Do not turn the key off, start the engine, turn on any accessories or unplug the programmer.

Items you will need

About the Author

In 1990 David Marsh began writing a column in the "Idaho Falls Post-Register" titled "Good Things," which presented restaurant reviews, sports analysis and movie criticism. Besides newspaper columns, Marsh researched police procedures for the Federal government. He has a Bachelor of Arts in administration and a Bachelor of Science in journalism from the University of Utah.