The Electronic Control Module (ECM) is the computer which controls the engine. The personality module contains the software that determines the function of the ECM. The two must be used together.
The ECM consists of the following items:
- A microprocessor that will execute the following ECM functions: governing, injection timing control, system diagnostics and data link communication
- A permanent memory that stores programmable parameters and diagnostic codes
- Input circuits that filter electrical noise from sensor signals
- Input circuits that protect internal circuits in the ECM from potentially damaging voltage levels
- Output circuits that provide high voltage for the injector solenoids and for relays
- Output circuits that provide a clean, stable power source for engine components
The personality module consists of the following items:
- The personality module contains all of the software for the ECM. Updating the personality module to a different version may cause some engine features to behave differently.
- Control maps define such operating conditions as timing and fuel rates. These maps help to achieve optimum engine performance and fuel consumption. The maps are programmed into the personality module at the factory.
The personality module on earlier engines could be updated only by the removal of the module from the ECM. A module that contained a different program would then be installed. A new type of memory chip which can be programmed through the use of the Caterpillar Electronic Technician (ET) is now used. This is called "FLASH" memory. "FLASH" memory has the advantage of retaining programmed information indefinitely and "FLASH" memory can be reprogrammed without opening the case of the ECM. This process of flash programming is accomplished through the use of Cat ET. Refer to the diagnostic procedure Troubleshooting, "Flash Programming".
Note: The personality module can still be removed and replaced. Flash Programming is the preferred method for reprogramming a personality module.
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| Illustration 1 | g00589030 |
Electronic Control Module (ECM) | |
Test Step 1. Check for "ACTIVE" Codes.
- Turn the keyswitch to the OFF position.
- Start Cat ET.
- Turn the keyswitch to the ON position. The engine should be off.
- Check for active diagnostic codes.
Results:
- 253-02 Present - This code indicates that there is a mismatch in the interlock code for the personality module. The interlock code that is stored in the ECM does not match the interlock code of the personality module.
Repair: Refer to the diagnostic procedure Troubleshooting, "System Configuration Parameters" for additional information.
Stop.
- 254-12 Present - If an internal problem develops, the diagnostic code 254-12 becomes active. This indicates that the ECM has detected an internal problem that cannot be fixed.
Repair: Replace the ECM. Ensure that the new ECM serial number ends in CD. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM" before replacing the ECM.
Stop.
- 268-02 Present -
Repair: Reprogram the system configuration parameters. Refer to the diagnostic procedure Troubleshooting, "System Configuration Parameters" for additional information.
Stop.