LEAD AS 4N9404 - Caterpillar

System Operation Description: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 relays
Power circuits that provide a clean, stable, electrical power for the injector solenoids, internal circuits, and external sensorsThe 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.
Illustration 1 g00589030
Personality Module
Test Step 1. Check for "ACTIVE" Diagnostic Codes.
Turn the ECS to the OFF/RESET position.
Turn the battery disconnect switch to the OFF position.
Connect Cat ET to the service tool connector J60. Start Cat ET.
Turn the battery disconnect switch to the ON position.
Turn the ECS to the STOP position. The engine should be off.
Check for active diagnostic codes. Results:
253-02 Present - Proceed to Test Step 2.
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, "Programming Parameters" for additional information.STOPTest Step 2. Check for a Personality Module Mismatch.
Verify that the correct ECM has been installed.
Check the ECM part number. Check the last two characters of the ECM serial number. Expected Result:The ECM serial number ends with a CD.Results:
OK - The serial number of the ECM ends with a CD. Verify that the correct personality module is installed.Repair: Connect Cat ET and