Microprocessor

234

TM 9-2320-312-24-2

Troubleshooting Section

The Engine Control Module (ECM) is the computer

which controls the Caterpillar electronic truck

engine. The Personality Module contains the

software that controls the operation of the computer

(ECM).

The Personality Module software is the instructions

that are used by the ECM to control the engine. For

this reason, updating the Personality Module to a

different version may cause some engine functions

to behave in a different manner.

Performance Maps

Performance Maps define characteristics for various

operating conditions. These characteristics are used

to achieve optimum performance while emissions

requirements are being met. Examples of these

characteristics are included in the following list:

Fuel rate

g00772334

Illustration 76

Timing

ECM and harness connectors

These characteristics are programmed into the

Logged Diagnostics

Personality Module at the factory only.

Logged diagnostics are stored by the ECM into

Microprocessor

memory so a permanent record of the diagnostic

code is retained. Logged faults that are not critical

The ECM uses a microprocessor to perform the

are automatically cleared after 100 hours.

computing that is required to perform the following

functions:

Input Circuits

Governing

Input circuits filter electrical noise for sensor signals.

Also, input circuits protect internal circuits from

Controlling timing

potentially damaging voltage levels.

Generating diagnostic codes

Output Circuits

Communicating with service tools

Output circuits provide the voltage or current

that is required to energize components that are

The microprocessor reads the instructions from the

connected to the ECM.

software in the Personality Module.

Power Circuits

Programmable Parameters

Power circuits provide clean stable electrical power

Programmable Parameters are stored in permanent

to internal circuits and external sensors.

memory. This includes both Customer Specified

Parameters and System Configuration Parameters.

Test Step 1. Inspect Electrical Connectors

Refer to Troubleshooting, "Customer Specified

and Wiring.

Parameters" for details on Customer Specified

Parameters and refer to Troubleshooting, "System

A. Thoroughly inspect ECM vehicle harness

Configuration Parameters" for details on System

connector J1/P1 and the battery connections.

Configuration Parameters.

Refer to Troubleshooting, "Electrical Connectors

- Inspect" for details.

B. Perform a 45 N (10 lb) pull test on each of the

following wires in the ECM connector:

Ignition key switch (terminal 70)