426 Section 4 Computer Control Technology Copyright Goodheart-Willcox Co., Inc. is needed to check for updated PROMs that should be installed and calibration programs that should be downloaded to the new computer. External identifica- tion numbers are not always placed on the PROM. When removing a computer, the ignition key should be off and the vehicle’s negative battery cable discon- nected. This will prevent voltage spikes from damaging the computer when the harness connectors are removed. Remove any shields or components necessary to access the computer. Unbolt the brackets holding the computer in place and unplug the computer connectors. Identification information is usually stamped or printed on the computer. Use this data and the year, make, and model of vehicle to order the correct replacement computer. The VIN (vehicle identification number) may be helpful, as well. Caution When handling computers, keep one hand on chassis ground and use the other to remove the component. This will prevent a static electrical charge from enter- ing and damaging the electronic circuitry. If avail- able, wear an anti-static wrist strap when working on computer circuits. Static electricity may not instantly ruin an electronic part, but it can reduce the part’s useful service life from years to days. EEPROM Programming Using Computerized Equipment Most newer computers use Electrically Erasable Programmable Read Only Memory (EEPROM) or Flash Erasable Programmable Read Only Memory (FEPROM) chips that are permanently soldered to the circuit board. These chips must be programmed using electronic equipment. They are often reprogrammed to correct driveability and performance problems. EEPROMs are programmed using a method referred to as flash programming. Flash programming may be performed by downloading the vehicle’s infor- mation through a computer, a computerized diagnostic analyzer, or a scan tool. Actual programming details vary between manufacturers, but the basic procedure begins by placing the computer in the programming mode. One of two methods is used to program the computer: • Direct programming using a service computer or a laptop computer, Figure 25-12. • Remote programming with the computer off the vehicle. Direct Programming Direct programming is the fastest and simplest method. The new information is downloaded by attaching a shop recalibration device (usually a laptop computer) directly to the data link connector. The erasure and programming is done by accessing the programming menu and following the instructions as prompted by the computer. Then, the vehicle’s operat- ing information and parameters are entered into the vehicle’s computer through the connector. Remote Programming Remote programming is done with the vehicle’s computer removed from the vehicle. This procedure is used when changes need to be made through a direct modem connection to a manufacturer’s database computer. It can also be done in cases where direct programming is not practical or possible. Since special connectors and tools are required for this type of programming, this procedure is done only at new vehicle dealerships. EEPROM Programming Procedure To begin programming the EEPROM-equipped computer, make sure that the vehicle’s battery is fully charged. Recharge the battery if necessary. Do not charge the battery during the programming procedure, as damage to the computer will result. Connect the programming computer or scan tool to the data link connector. Make any other vehicle connections as needed before proceeding with the programming sequence. Caution Do not disconnect the scan tool or programming computer from the data link connector during the programming sequence. Doing so will damage the vehicle’s computer. To start the programming sequence, the program- ming computer prompt may ask you to enter the engine type, vehicle type, and vehicle identification number (VIN) in a specific sequence. Once the vehicle information is entered, go to the programming soft- ware and follow the directions as prompted.