How to Reprogram an Auto Computer

by Y.T. Lin

An outdated or corrupt engine management software can make the auto computer send misleading information to the driver, for example, turning on a dash light when there is nothing wrong with the vehicle. This is one of the reasons a reprogramming is necessary. Reprogramming or updating the computer is possible only on vehicles produced after 1996. Earlier vehicles still need to have the computer module replaced in the event of outdated or damaged software in the ROM chip.

Request the manufacturer's engine computer updating software from the car dealer or the manufacturer. Contact the dealer or manufacturer through their websites or call their customer service centers. They will mail the software CD to your address or have you download it to PC.

Install the program onto your PC once you receive the CD if you chose this method to get the software. The software will be unzipped and with a shortcut icon added to your desktop.

Purchase a vehicle diagnostic scanner at a auto parts store. The scanner normally has a scanner cable included in the package. If not, buy a scanner cable separately.

Plug one end of the USB cable into the scanner and the other end into the PC.

Plug the power cord into a wall outlet and turn on the diagnostic scanner. Information and choices will appear on the LCD screen. Select the "Import" or "Save..." option on the LCD by pressing the appropriate buttons on the scanner.

Click "Start," "Computer" on the PC and double-click the hard drive that you saved the software on. Locate the folder containing the software. Unzip the software if you downloaded it from the Internet; double-click to open the software folder, and then right-click once on the sub-folder that has the ZIP extension. Click "Extract."

Drag the software from PC to the diagnostic scanner. The process is the same as dragging files on your computer or to other media storage devices with the mouse.

Disconnect the diagnostic scanner from the PC once the software is transferred.

Position the car key in the "On" position, which is the first stop on the ignition switch.

Locate the vehicle's diagnostic port that is usually beneath the dashboard near the steering column. The port is likely protected by a plastic cover which can be pried open with your fingers. The cover for the port, if present, is about 1-by-1-inch in size.

Insert the scanner cable into the vehicle's diagnostic port. Plug the other end of the cable into the diagnostic scanner. The scanner cable ends goes in only one way. You will know which end goes into which port when fitting the first end into the diagnostic port.

Plug the diagnostic scanner power cord into a wall outlet or your vehicle's electrical outlet.

Press the power button on the scanner. Once the scanner is on, it will automatically detect the computer for your vehicle and erase the original program in the ROM chip. After the erasure, the scanner will load the new software that you received from the manufacturer into the chip. The updating process is displayed on the scanner's LCD.

Turn off the scanner, and detach the scanner cable and the power cord once the reprogramming is done on the vehicle's engine computer.

Replace the plastic diagnostic port cover as needed.

Turn on the car engine. Any false warning lights previously on will be off after a few seconds.


  • check Update or reprogram your vehicle's computer every three years to ensure its efficiency and normal functioning. This is important to California drivers, as California is one of the strictest regulatory states in the U.S. on vehicle emissions and operations. Vehicle tune-up service usually includes the reprogramming of the auto's computer; ask the mechanic if you're not sure.


  • close Use only the newest software when reprogramming the computer. Software updates for your vehicle may occur every few years. Do not drag the desktop updating software icon onto the diagnostic scanner. The icon is just a shortcut to open the program; it does not contain the actual program files.

Items you will need

About the Author

Y.T. Lin has been writing articles professionally since 2008 and for other content websites relating to his field of expertise since 2004. Lin holds Bachelor of Fine Arts and Master of Arts degrees in graphic design and interior design, respectively, from the Academy of Art University in San Francisco. He is a professional digital graphic artist, interior designer and Web developer.