478 Auto Electricity and Electronics
in the programming mode. One of three methods is used to
program the computer:
❑
Direct programming using a service computer or com-
puterized analyzer.
❑
Indirect programming using a scan tool and a com-
puter or computerized analyzer.
❑
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 computer or computerized
analyzer) 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 operating information and
parameters are entered into the vehicle’s computer through
the connector.
Indirect Programming
To perform indirect programming, the proper scan
tool must be available to connect to the programming
computer and to the vehicle, as well as to reset some com-
puter-controlled vehicle systems after programming. The
programming computer may resemble the personal com-
puter (PC) used in the home, or it may be a computerized
analyzer like the one used for direct programming.
In this type of programming, the vehicle information
is downloaded from the PC or computerized analyzer into
the scan tool. It is then downloaded from the scan tool into
the vehicle’s computer. The scan tool menu is accessed
using the keypad. Most scan tools will use a high-capacity
generic program cartridge to store the information. Some
newer scan tools have suffi cient fi xed memory to hold the
information and, therefore, do not use a separate program
cartridge. In either case, follow the manufacturer’s proce-
dure as prompted.
Remote Programming
Remote programming is done with the vehicle’s com-
puter 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 or indirect program-
ming 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 com-
puter, make sure the 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 service computer or scan tool to the
computer data link connector. Make any other vehicle con-
nections as needed before proceeding with the program-
ming sequence.
Caution: Do not disconnect the scan tool or
service computer from the data link connector
during the programming sequence. Doing so
might damage the vehicle’s computer.
To start the programming sequence, the analyzer or
scan tool prompt may ask you to enter the engine type,
vehicle type, and vehicle identifi cation number (VIN), in a
specifi c sequence. Once the vehicle information is entered,
go to the programming software and follow the directions
as prompted.
Depending on the manufacturer, it may be necessary to
turn the ignition switch on or off during the connection and
programming procedure. Double-check any instructions on
ignition switch position before making any connections or
beginning computer erasure and programming. The next step
is to determine the type of programming that is needed.
Programming a New Computer
If a new computer is being installed, it may require
programming. In many cases, other on-board computers
can be accessed and programmed using the data link con-
nector. While most computers have internal circuitry that
protects them from accidental programming, be careful not
to program the wrong computer. Do not attempt to program
a new computer with information for the old computer or
a computer from another vehicle. Any attempt to do this
will set a failed programming sequence code in the new
computer’s memory.
Note: In some cases, an erasure may need
to be performed on a new computer before
initial programming can take place.
Reprogramming Computers
If you are reprogramming a vehicle’s computer, deter-
mine the date the current programming was downloaded
or the program’s calibration number. If the information
installed is the latest version, no further actions are required.
If the latest information has not been downloaded, proceed
with the reprogramming sequence.
Before reprogramming most computers, you must fi rst
erase the existing information. After this step is complete,
select the updated calibration information from the repro-
gramming computer or scan tool menu. Then download
the new information into the computer. On some systems,
the erasure step is not necessary as the service computer or
scan tool will erase or overwrite the old information as it
loads the new program into the computer.