Where In The Control Module Is the Program Data Stored?

Where Is The Program Data Stored In A Control Module?

The difference between the personal computer and the engine control module is where the data is stored. The computer uses the hard drive, while the engine control module uses either an EPROM or an EEPROM depending on the engine control system.

EPROM (Electrically Programmable Read Only Memory)
- Used in all M3.X Systems.







An EPROM is a removable chip with multiple connector pins which plug into the printed circuit of the control module.
When re-programming this type of control module, the EPROM must be removed and a new "blank" EPROM installed prior to programming.

EEPROM (Electrically Erasable Programmable Read Only Memory)
- Used in M5.X (Bosch) and MS (Siemens) systems.
- Used in GS 8.55 Transmission Control System.







An EEPROM is a soldered in chip which is not removable from the control module. As their name implies, EEPROMS can be electrically erased and reprogrammed without opening the control module. This is known as "Flash programming".

In either case, the E or EE PROM stores the loaded program data including:
- Characteristic maps for; Ignition, Injection, Purge control, etc...
- Characteristic curves
- Control constants

When the PC is switched on it causes the system to boot up and be ready for operation. When you enter a command on the key board (input), the computer processes the data and carries out a control function (output) like operating a printer.

Like the PC, switching the ignition "ON" supplies power to the engine control module allowing it to be ready to receive input data and carry out functions based on the loaded software. See Tab 6 for complete engine control module programming information.