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Electronic Controls
The ECM consists of two main components, the control computer (hardware) and the Personality Module (software). The control computer is the microprocessors and electronic circuitry. The Personality Module contains the software for the control computer and stores operating maps that define power and torque curves. The two components work together to control the engine.The ECM determines a desired engine speed based on the throttle position and other sensor input signals and certain diagnostic codes. The ECM maintains the desired engine speed by sensing actual engine speed using the Speed/Timing Sensor, then determines how much fuel to inject in order to achieve the desired engine speed. Some operating conditions (cold mode, derates, diagnostic codes and events) will alter engine speed from the desired engine speed.Fuel Injection
The ECM controls the amount of fuel injected by varying signals to the unit injectors. The unit injectors will inject fuel ONLY when the injector solenoid is energized. The ECM sends a 105 volt signal to the solenoid to energize it. By controlling the timing and duration of the 105 volt signal, the ECM can control injection timing and amount of fuel injected.The ECM limits engine power and modifies injection timing during COLD MODE operation to increase startability, reduce warm-up time, and reduce white smoke. COLD MODE may be activated whenever the engine temperature falls below a predetermined value and remains active until the engine temperature rises above a predetermined value or a time limit is exceeded.The ECM sets certain limits on the amount of fuel that can be injected. FRC Fuel Pos is a limit based on air-to-fuel ratio for exhaust smoke control purposes. The ECM can sense a higher turbocharger compressor outlet pressure (more air into cylinder) to increase the FRC Fuel Pos limit to allow more fuel into the cylinder. Rated Fuel Pos is a limit based on the power rating of the engine. It is similar to the rack stops and the torque spring on a mechanically governed engine. The Rated Fuel Pos provides power and torque curves for a specific engine family and rating.The two limits (FRC Fuel Pos and Rated Fuel Pos) are programmed by the factory into the Personality Module and are not programmable in the field.Injection timing depends on engine rpm, load, and other operating factors. The ECM knows where top center (TC) of every cylinder is from the signal provided by the engine Speed/Timing Sensor. The ECM decides when injection should occur relative to the piston top center position and provides a signal to the injector at the desired time.Programmable Parameters
System Configuration Parameters are parameters stored in the ECM that affect engine operation. The parameters are set at the factory and may be changed with an Electronic Service Tool ( ET - Electronic Technician or ECAP - Electronic Control Analyzer Programmer). However, a factory password may be required to change certain parameters.Self-Diagnostics
The Electronic Control Module has some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and an audible or visible alarm may be present at the cab display monitor. In most cases, the code is also stored in permanent memory in the ECM.Current Diagnostic Codes are referred to as ACTIVE. They indicate that a problem of some kind currently exists. They should always be serviced first. Refer to Section 4: Troubleshooting With A Diagnostic Code for more details.Diagnostic Codes stored in memory are called LOGGED. The problem may have been temporary or may have been repaired since the time it was logged. It is important to remember that it is possible to log faults whenever a component is disconnected and the keyswitch is in the ON position. Therefore, logged diagnostic codes do not necessarily mean something needs to be repaired. Logged diagnostic codes can be helpful when troubleshooting intermittent problems.In addition to diagnostic codes, the ECM also records EVENTS (such as high coolant temperature or low oil pressure) that have occurred, rather than diagnostics or electronic failures. Refer to Section 4: Troubleshooting With a Diagnostic Code for more details.Passwords
The System Configuration Parameter Full Load Setting and most Logged Events are protected by Factory Passwords. Factory Passwords are calculated on a computer system available only to Caterpillar dealers. Refer to Section 2: Programming Parameters for details regarding when passwords are needed and how to obtain them.Engine System Diagram
Figure 1.1 - 3176C & 3196 Engine SystemBasic Electronic System Diagram
Figure 1.2 - 3176C & 3196 Engine Electronic SystemSensor and Connector Locations
Figure 1.3 - 3176C Engine ViewElectrical Connectors And Functions
Figure 1.4 - Deutsch DT Style Connectors
Figure 1.5 - P1 & P2 Connectors (40-Pin Deutsch AEC)
Figure 1.6 - Electronic Control Module (40-Pin Deutsch AEC)Engine Connector And Wiring Information
The schematics are revised periodically and will change with wiring harness updates. For the most current information, always check the revision number printed on the schematic and use the schematic that corresponds to the specific engine serial number. Schematics are referenced periodically in this Troubleshooting Manual.Harness Wire Identification
Caterpillar identifies all wires with eleven solid colors. In addition to the eleven solid colors of wire, a circuit number is stamped on each wire. The circuit number is stamped approximately every 25 mm (1 in) for the length of the wire. For example, a color code of A701-GY on the schematic would denote a gray wire with the circuit number A701 stamped on it. This wire is the solenoid signal wire (power) for Cylinder No. 1(CYLINDER HEAD SOL 1) on the Electronic System Wire Harness. The A701-GY color code will be the identification of SOLENOID 1 POWER circuit on all Caterpillar electronic engine wire harnesses with Electronic Unit Injectors.Another wire identification on the schematic is the size of the wire. The size of the wire will follow the wire color. Wire size or gauge is referred to as AWG, which