3176C ENGINE FOR USE IN CPT372 & Caterpillar

Section 1: Electronic System Overview

Usage:

System Operations

The 3176C 6 Cylinder Engines utilize Electronic Unit Injectors. These injectors are mechanically actuated and electronically energized. The injector solenoid is mounted on top of the injector body along side the rocker and return spring.

Electronic Controls

The 3176C 6 Cylinder Engines electronic system consists of the Electronic Control Module (ECM) and engine sensors. The ECM is the computer which controls the engine operating parameters. The Personality Module in the ECM contains the software which controls how the ECM behaves (the personality module stores the operating maps that define power, torque curves, rpm, etc). The injection pump, fuel lines and fuel injection nozzles used in mechanical engines have been replaced with an electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel delivered by the injector. The Electronic Control Module (ECM) sends a signal to each injector solenoid to provide complete control of the engine. The ECM determines a "desired speed" based on the throttle signal, PTO switches (only while in PTO mode) and certain diagnostic codes. The ECM then maintains the desired engine speed by sensing actual engine speed and deciding how much fuel to inject in order to achieve the desired speed.

Engine Governor

The Electronic Controls on the engine serve as the engine governor. The Electronic Controls determine when and how much fuel to deliver to the cylinders based on the actual and desired conditions at any given time.

The governor uses the Throttle Position Sensor to determine the desired engine speed and compares this to the actual engine speed determined through the Engine Speed/Timing Sensor. If desired engine speed is greater than the actual engine speed, the governor injects more fuel to increase engine speed.

Timing Considerations

Once the governor has determined how much fuel is required, it must next determine when to inject the fuel. Injection timing is determined by the ECM after considering input from the Coolant Temperature Sensor, Inlet Air Manifold Temperature Sensor, Atmospheric Pressure Sensor, and Turbocharger Outlet (Boost) Pressure Sensor. The ECM determines where top center on cylinder number one is located from the Engine Speed/Timing Sensor signal. The ECM decides when injection should occur relative to top center and provides the signal to the injector at the desired time. The ECM adjusts timing for best engine performance, fuel economy and white smoke control. Actual or Desired Timing cannot be viewed with an Electronic Service Tool.

Fuel Injection

The ECM controls the amount of fuel injected by varying signals to the injectors. The injectors will pump fuel ONLY if the injector solenoid is energized. The ECM sends a high voltage signal to energize the solenoid. By controlling the timing and duration of the high voltage signal, the ECM can control injection timing and the amount of fuel injected.

The Personality Module inside the ECM sets certain limits on the amount of fuel that can be injected. FRC Fuel Pos is a limit based on boost pressure to control the air/fuel ratio for emissions control. When the ECM senses a higher boost pressure (more air into cylinder), it increases the FRC Fuel Pos limit (allows more fuel into cylinder).

Rated Fuel Pos is a limit based on the power rating of the engine and rpm. It is similar to the rack stops and torque spring on a mechanically governed engine. It provides power and torque curves for a specific engine family and rating. All of these limits are determined at the factory in the Personality Module and cannot be changed.

Figure 1.1 - Fuel Injection

Customer Parameters Effect on Engine Governing

A unique feature with Electronic Engines is the Customer Specified Parameters. These parameters allow the engine owner to fine tune the ECM for engine operation to accommodate the typical or specific usage of the engine.

Many of the Customer Parameters provide additional restrictions on the action the ECM will take in response to the operators' input. For example, the Top Engine Limit is an speed limit the ECM uses as a maximum speed for fuel delivery to the injectors. The ECM will not fuel the injectors above this speed.

Some parameters are intended to notify the operator of potential engine damage such as the Engine Monitoring Parameters. Other parameters are provided to enhance the engine installation or provide engine operating information to the engine owner.

ECM Engine Monitoring Parameters

The ECM Engine Monitoring Mode determines the level of action taken by the ECM in response to a potentially engine damaging condition. There are four customer selectable levels:

- Default = WARNING

Alternative = OFF

Alternative = DERATE

Alternative = SHUTDOWN

ECM Engine Monitoring Programmed OFF

The ECM will not indicate low oil pressure, high inlet air temperature, or low coolant level. Coolant Temperature will continue to be used for Cold Mode and cooling fan control. Inlet Manifold Air Temperature is used for low ambient temperature operation and for cooling fan control.

ECM Engine Monitoring Programmed to WARNING

If Engine Monitoring is programmed to Warning, the ECM monitors oil pressure, coolant temperature, inlet manifold temperature, and coolant level (if sensor is installed and enabled). The following table indicates the diagnostic event codes (EID) available, and their effect on engine performance when active. The Diagnostic Lamp will flash and the Alarm Lamp will come ON as indicated in the table when the diagnostic code is active.

ECM Engine Monitoring Programmed to DERATE or SHUTDOWN

If Engine Monitoring is programmed to Derate or Shutdown, the ECM will alter engine performance when operating parameters are exceeded. Whenever the engine is derated, the Diagnostic Lamp and Alarm Lamp will flash. For the DERATE column in the following table, POWER indicates engine power is limited [maximum derate is 119 kW (160 hp)]. RPM indicates engine rpm is limited (maximum derate is 1350 rpm). Refer to the corresponding Engine Component Overview section for operating conditions causing these event codes.

ECM Engine Monitoring Time to SHUTDOWN

The following table indicates active diagnostic codes capable of shutting down the engine when the ECM is programmed to Shutdown. The Time To Shutdown column indicates the minimum time before the engine will shut down if the engine has already been running for at least 30 seconds. Start/Restart Time indicates running time if the diagnostic code is active when the engine starts, or following an Engine Monitoring caused shutdown. NO indicates the diagnostic code will not shut down the engine. Note these times assume the condition causing the diagnostic code exists continuously and is not intermittent

Self-Diagnostics

The electronic system has some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and the Diagnostic lamp will begin to FLASH the Diagnostic code. In most cases, the code is also stored in permanent memory (Logged) in the ECM.

Diagnostic Fault Codes

When diagnostic codes occur, they are called Active. They indicate a problem of some kind currently exists. They should always be serviced first. If the engine has an Active Code, find the code in Troubleshooting With A Diagnostic Code section and proceed to the appropriate Functional Tests section to diagnose the cause. Diagnostic codes stored in memory are Logged. Since the problem may have been temporary or may have been repaired since the time it was logged, logged codes do not necessarily mean something needs to be repaired. They are instead meant to be an indicator of probable causes for intermittent problems. Some of the codes require passwords to clear. Codes not requiring passwords to clear are automatically deleted from memory after 100 engine operating hours.

Operating Information Stored in the ECM

The ECM uses a second battery connection to maintain a portion of memory used for Engine Operating Data when the keyswitch is OFF (ECM is not powered). Disconnecting this line does not affect the ECM stored Factory/Customer Parameters, or logged diagnostic codes. Interrupting this connection causes the ECM to lose some portion of the engine operating information, or trip information as explained in the following paragraphs.

NOTE: The ECM accumulates the Total Data in memory dependent on the Unswitched +Battery connection.

When the data reaches 2 hours (time parameters) or 150 liters (40 US gallons) for fuel used parameters, the ECM transfers this quantity to permanent memory. For example, if you disconnect ECM Connector J1/P1 (disconnecting the Unswitched +Battery connection), the ECM Totals may vary by as much as one-half of these values [1 hour or 75 liters (20 US gallons)], but no more.

Cold Mode

Cold Mode is activated whenever coolant temperature is below 17°C (63°F). In Cold Mode engine power is limited, timing is advanced, and low idle is adjusted (800 rpm for the 6 Cylinder Engines). Once activated, cold Mode will continue until the engine has been running for 5 minutes. The ECM then causes the engine to leave Cold Mode, low idle is returned to the rpm set by the Customer Specified parameters and normal engine operation is restored.

Lifetime Totals Stored In The ECM

The ECM maintains engine total data for the following parameters.

Engine Hours is engine running hours (it does not include time when the ECM is powered ON without the engine running).

Idle Hours and Idle Fuel can include time when the engine speed is set using the PTO switches and the speed is within range or the PTO speed limit parameter, but the engine is not operating under load. Fuel Information can be displayed in US gallons or liters.

Engine Load Factor provides relative engine operation information (how hard the engine has been operated compared to the maximum), and is determined using maximum Fuel (maximum fuel the engine can use during operation), Idle Fuel, and Fuel Used. All of these parameters are available using an Electronic Service Tool within the trip Data menu.

Trip Data Stored In The ECM

Trip data allows the owner of the unit to track engine operation over owner defined intervals. Trip Data includes Engine Hours, Fuel Consumption, Idle Hours, Idle Fuel and Average Load Factor.

Two types of data are stored in the ECM, Engine Data and Operation Histogram Data. Data can be reset at any time by requesting with an Electronic Service Tool. The data is stored in memory maintained through the Unswitched +Battery connection when the keyswitch is OFF. Disconnection of the Unswitched +Battery line will reset or clear this data.

Histograms

The Engine Speed (RPM) Histogram records engine operation time spent in engine rpm ranges from below 600 rpm to above 2100 rpm (in 100 rpm increments). The Electronic Service Tool calculates the percentage of time spent in each of the engine rpm ranges. The Load Factor Histogram records operation from 0 to 100 percent in 20 percent increments using the same parameters as Engine Speed Histograms.

Fuel Correction Factor

A Customer Password protected Fuel Correction Factor is available for fine tuning fuel used calculations. This can be used to enhance the accuracy of the fuel used calculation. Altering the Fuel Correction Factor does not affect data already stored in the ECM, only data stored after it is entered. NOTE: The Fuel Correction Factor should be adjusted based on a long interval, using actual tank data and the ECM record data.

Maintenance Indicator Data

The ECM records the previous maintenance point for three levels of maintenance. PM Level 1, PM Level 2 and Coolant Flush/Fill. The previous maintenance point is used by the ECM to calculate when the next maintenance is due. The Maintenance Indicator feature is programmable to hours. The PM Level 1 maintenance is programmable to OFF, Automatic Hours, or Manual Hours. If PM Level 1 is programmed to Automatic, the ECM calculates the next maintenance due by considering the operation history from the previous maintenance interval. If the engine has a history of poor fuel economy, the maintenance interval is less than an engine with better fuel economy. The ECM uses the engine oil capacity also, with a larger capacity providing a longer maintenance interval. If the PM Level 1 Maintenance Indicator is programmed to Manual, the owner can program in their own specific maintenance intervals. PM Level 2 and Coolant Flush/Fill intervals are determined by the factory.

Programmable Parameters

Certain parameters that affect 6 Cylinder Engine operation may be changed with the Electronic Service Tools. The parameters are stored in the ECM and are protected from unauthorized changes by passwords. These parameters are either "System Configuration Parameters" or "Customer Parameters".

System Configuration Parameters are set at the factory and effect emissions or power ratings within a family of engines. Factory Passwords must be obtained and used to change System Configuration Parameters.

Customer Parameters are variable and can be used to affect speed limits, rpm/power ratings within the limits set by the factory. Caterpillar Engine Monitoring and PTO operation can also be affected. Customer Passwords are necessary to change Customer Specified Parameters.

Customer Parameter Lockout allows restricted access to changing some available parameters. Locking out a parameter required customer passwords (if customer passwords have been programmed). Once a parameter is locked out, factor passwords are required to change the parameter or unlock the parameter.

* Lockout Options

* Engine Rating

* Engine Monitoring Mode

* Power Trim

* Top Engine Limit

* High Idle

Some parameters may affect engine operation in ways a operator does not expect. Without adequate training, these parameters may lead to power or performance complaints, even when the engine is performing to specification. Read Section 2: Programming Parameters for more details.

Passwords

"System Configuration Parameters" are protected by Factory Passwords. Factory passwords are calculated on a computer system available only to Caterpillar dealers. Since factory passwords contain alphabetic characters, only an ECAP or Caterpillar Electronic Technician may change System Configuration Parameters. System Configuration Parameters affect power family or emissions. "Customer Parameters" are protected by Customer Passwords. See section Section 2: Programming Parameters for more details when passwords are needed and how to obtain them.

Diagnostic Lamp

The Diagnostic Lamp is required to indicate a control system malfunction (diagnostic condition) to the operator for diagnosing control system component failures. Count the flashes (this is the first digit), a brief pause will occur, the second digit of the flash code will follow. All active or logged codes (occurring since ECM received power) will follow in the same manner with a five second pause between codes.

NOTE: It is suggested the Diagnostic Flash Codes be used only to indicate the nature of a diagnostic code occurrence, not to perform detailed troubleshooting.

Warning Lamp

The Warning Lamp is used to indicate the existence of a Caterpillar Engine Monitoring detected problem. The lamp is for Caterpillar Engine monitoring, and used only when the Customer Parameter for Engine Monitoring is set to any mode other than OFF. The Warning Lamp should illuminate for a minimum of two seconds following engine start. If the oil pressure is insufficient the Warning Lamp will stay illuminated until the oil pressure reaches an acceptable pressure. The Coolant Temperature, Inlet Air Manifold Temperature, and Coolant Level Sensors will not affect the Warning Lamp for the first 30 seconds following engine start up. If the Customer Parameters for Engine Monitoring is set to "OFF", the Warning Lamp should not operate and is unnecessary. If the Customer Parameter for Engine Monitoring is set to "Warning", "Derate" or "Shutdown" the Warning Lamp will illuminate continuously when a warning condition exists. If the Customer Parameter for Engine Monitoring is set to "Derate" or "Shutdown", the lamp flashes whenever engine monitoring is "Derating" engine speed, vehicle speed, and power. If the Customer Parameter for Engine Monitoring is set to "Shutdown" the Warning Lamp will continue to Flash following the "Derate" mode until the engine is shutdown.

Maintenance Lamp

The lamp will be ON when the programmed interval is met. The ECM records data related to vessel maintenance. When Hours is selected (Manual-Hours or Automatic-Hours), then all maintenance indicators (PM1, PM2, Coolant Flush/Fill) on the Electronic Service Tool will be in hours. The ECM provides PM1 maintenance interval and last maintenance information.

Engine Shutdown Switch

The Engine Shutdown Switch is wired in series between Customer Connector P3/J3 pin-27 and -Battery. A normally open (N/O) switch should be used so that when the switch closes pin-27 is connected to -Battery and the ECM disables current to the fuel injectors. Application details of this feature will vary depending on the desired effect. Grounding of the Shutdown Switch does not disable power to the ECM. The ECM will remain powered even after the Shutdown Switch has been closed.

Emergency Stop Control

The Emergency Stop Control driver signal is provided by the ECM to control the Air Shutoff Valve (if equipped) based on input from the Engine Speed Sensor or Overspeed Verify Switch. The circuit provides a 3.5 Amp Pulse Width Modulated (PWM) signal to drive the valve if installed. The Emergency Stop logic will turn On the driver when:

* Engine Speed is greater than 2500 rpm OR... Overspeed verify Switch is grounded AND engine speed is greater than 1875 rpm.

The Primary and/or Secondary (Backup) engine Speed Sensor(s) are the only Caterpillar sensors that affect the Emergency Stop Driver logic. If the engine runs the Engine Speed/Timing Sensor(s) are functioning properly and should not be suspect when troubleshooting and Emergency Stop problem. The optional Overspeed Verify Switch provides for a means to check the system function at 75 percent of the overspeed set point.

Ether Injection System

The engine ECM controls the ether system to improve the cold starting capability. The ECM uses the Coolant Temperature Sensor to control ether injection. The ECM uses actual engine rpm to determine if ether should be injected. The ether control logic assumes a "continuous" ether system is being utilized and the duration of injection is a linear function of coolant temperature. The automatic ether injection circuit turns ON the relay driver when the following conditions are met. The engine speed must be between 30 rpm and 1500 rpm and the coolant temperature is between -40°C and 10°C (-40°F and 50°F). The ether injection time is selected from a linear relationship between -40 and 10°C (-40 and 50°F). The end points of this function are -40°C (-40°F) for 130 seconds, 10°C (50°F) for 15 seconds. Manual ether injection can occur between 30 and 1500 rpm if the coolant temperature is below 66°C (150°F) for a maximum time duration of 2 minutes. This will be enabled by a digital input (Ether Override Switch) connected to the customer connector on the engine harness.

Data Link

ATA Data Link

The ATA Data Link is used to communicate ECM information to the Electronic Service Tools. The ECM provides two ATA Data Link connection pins from ECM Connector J1.

NOTE: The ECM does not provide the power and -Battery connection to the Data Link Connector. This is important because it is possible for the Data Link Connector to have battery power when the ECM is not powered up, resulting in an "Unable to communicate with ECM" message.

CAN Data Link (J1939)

The J1939 Data Link is used to communicate engine information to a J1939 Receiving Device. SAE J1939 is only supported on 6 Cylinder Engines with an ECM part number 118-7631 or 145-7805 AND the ECM must have a Personality Module with a Release Date of FEB98 or later. The J1939 Data Link can be used to monitor the following parameters: then list the CAN broadcast parameters.

The J1939 Data Link is used to communicate engine information to a J1939 Receiving Device. SAE J1939 is only supported on 6 Cylinder Engines with an ECM part number 118-7631 or 145-7805 AND the ECM must have a Personality Module with a Release Date of FEB98 or later.

NOTE: The Auxiliary Temperature and Pressure Sensor's use the PGN and not the J1939 Data Link.

CAT Data Link

CAT data link is a proprietary communication medium available on all Marine Engines. The connection is for communication with other microprocessor based devices such as the Electronic Control Module, GPS, EMS, or the Engine Vision Display.

SAE J1587 Data Link Broadcast Parameters

Engine Speed Controls

PTO Mode 1

PTO Enable Switch

The PTO Enable Switch is used to determine whether a Ramp Up and Ramp Down input signal should be acknowledged and responded to by the ECM.

PTO Ramp/UP Ramp/Down Switch

If the PTO Enable Switch is in the ON position, the Throttle Position Sensor is disabled and the desired engine speed is controlled using the Ramp Up/Ramp/Down Switch inputs.

NOTE: The ECM will use the higher selected speed when choosing from throttle input or PTO input. When the switch is toggled, the engine will respond according to the programmed PTO rpm Ramp Rate. When the switch is opened (released to center position), the engine will maintain the current desired engine rpm.

PTO Interrupt Switch

The PTO Interrupt is not enabled in Mode 1.

Intermediate Engine Speed Switch

The Intermediate Idle Switch is a (N/O) switch when connected to -Battery will ramp engine speed down to the customer programmable intermediate idle speed at the PTO speed rate. This will happen regardless of PTO set speed or throttle position sensor desired speed. When the Intermediate Idle switch is opened the engine speed will be ramped back up to throttle or PTO desired engine speed according to the PTO speed ramp rate. If the intermediate idle speed is programmed above current throttle/PTO desired engine speed, this switch will have no effect on engine speed.

PTO Mode 2

PTO Mode 2 default applies to the 3176C Engine and can be changed to PTO Mode 1 on the Electronic Service Tool if desired.

PTO Enable Switch

The PTO Enable Switch is used to determine whether a Ramp Up and Ramp Down input signal should be acknowledged and responded to by the ECM.

PTO Ramp/UP Ramp/Down Switch

If the PTO Enable Switch is in the ON position, the Throttle Position Sensor is disabled and the desired engine speed is controlled using the Ramp Up/Ramp/Down Switch inputs.

PTO Interrupt Switch

The PTO Interrupt switch is a normally open (N/O) switch. When connected to -Battery the PTO Interrupt switch will deactivate PTO mode and return the engine speed to the Desired Engine Speed based on throttle position. When the switch is open PTO operation is resumed.

Intermediate Engine Speed Switch

Engine Sensors

Oil Pressure Sensor

The ECM monitors oil pressure with a sensor located in the oil gallery. The ECM monitors oil pressure following engine start and can measure oil pressure from 0 kPa (0 psi) to 690 kPa (100 psi). The Oil Pressure Sensor is an absolute pressure sensor measuring oil pressure in the oil gallery. The difference between the pressure measured by this sensor (oil pressure) and atmospheric pressure is oil pressure as displayed on an Electronic Service Tool and communicated over the data link. The ECM uses this sensor input only if the parameter for Engine Monitoring is programmed to Alarm, Derate, or Shutdown.

The lack of oil pressure does not prevent the ECM from starting the engine. The ECM monitors oil pressure following engine start up and may display a Low Oil Pressure Alarm diagnostic code. The diagnostic code will not be logged for the first 15 seconds following engine start-up. The Oil Pressure Sensor measures pressure from 0 kPa (0 psi) to 690 kPa (100 psi). The sensor is supplied by the ECM with 5 VDC.

Oil Pressure Engine Monitoring

When Engine Monitoring is programmed to Alarm or Derate the following graph determines engine operation.

Figure 1.2 3176C Engine Oil Pressure Graph

Turbocharger Outlet Pressure

The ECM monitors Turbocharger Outlet Pressure (boost) through a sensor located inside the right side of the engine in the inlet manifold. Boost pressure is determined from the difference in pressure between Turbocharger Outlet Pressure and the Atmospheric Pressure. Boost pressure is used to reduce smoke emissions during acceleration. The ECM limits the amount of fuel injected until certain pressures are reached. The Turbocharger Outlet Pressure can measure pressure from 20 kPa (3 psi) to 340 kPa (49 psi).

Atmospheric Pressure Sensor

The Atmospheric Pressure Sensor monitors atmospheric pressure. Atmospheric Pressure sensing is used to reduce smoke emissions at high altitudes. The ECM optimizes timing bases on engine operating conditions.

Coolant Level Sensor (Optional)

Caterpillar Engine Monitoring (with the coolant level Sensor enabled) requires an OEM provided/installed Coolant Level Sensor to operate as a low Coolant Level Sensor. The sensor output will change status with the presence or absence of fluid at the sensing tip.

Primary and Backup Engine Speed/Timing Sensors

The Primary Engine Speed/Timing Sensor is used to determine both engine rpm and fuel injection timing. The sensor detects this information from a wheel on the camshaft. Timing calibration is performed by connecting a special magnetic sensor. The special timing calibration sensor senses motion of the crankshaft and is connected through an engine harness connector to the ECM.

Fuel Pressure Sensor

The ECM monitors fuel pressure following engine start and can measure fuel pressure from 0 kPa (0 psi) to 690 kPa (100 psi).

Inlet Air Manifold Temperature Sensor

The Inlet Air Manifold Temperature Sensor measure the temperature of the inlet air manifold. The ECM monitors the Inlet Air Manifold Temperature Sensor to adjust injection timing and to warn the operator of an excessive inlet air manifold temperature for engine monitoring.

Turbocharger Compressor Outlet Pressure Sensor

The ECM monitors boost through a sensor located inside the right side of the engine in the inlet manifold. Boost pressure is determined from the difference in pressure between turbocharger compressor outlet pressure and the atmospheric pressure. Boost pressure is used to reduce smoke emissions during acceleration. The sensor can measure pressure from 20 kPa (3 psi) to 340 kPa (49 psi).

Coolant Temperature Sensor

The Coolant Temperature Sensor measures the temperature of the engine coolant. The ECM uses this information to determine the mode of operation and if Caterpillar Engine Monitoring is not programmed to the OFF mode, to notify the operator of excessive engine temperature. Coolant Temperature is used to determine Cold Mode operation for the 6 cylinder engiens and is used for Engine Monitoring. In Cold Mode, timing is advanced and the fuel delivery is limited to improve cold engine operation. Cold Mode is not disabled if Engine Monitoring is programmed to OFF. Cold Mode Operation is activated whenever the coolant temperature is below 17°C (63°F) and the engine is not cranking. Cold Mode remains active until the coolant temperature rises above 17°C (63°F) or until the engine has been running for five minutes.

Coolant Temperature Engine Monitoring Operation

If Engine Monitoring is programmed to Derate, the ECM will cause the Check Engine Lamp to flash, and will also cause the Alarm Lamp to flash when the associated diagnostic code is active.

The flashing Alarm Lamp indicates the engine is in Derate mode. The following graphs indicate engine operation with Engine Monitoring Programmed to Derate. For 6 cylinder engines, High Coolant Temperature Alarm (110-00) and Very High Coolant Temperature (110-11) are triggered at 103°C (217°F) and 106°C (222°F) respectively.

If Engine Monitoring is programmed to Warning, the ECM will log the appropriate code and turn the Alarm Lamp ON. The ECM will not derate the engine if programmed to Warning.

Figure 1.3 Coolant Temperature Derate

If programmed to Derate, the ECM derates available power in four steps as temperature increases. Each step represents a reduction in available power of approximately 25 percent. The actual rate of change of power is limited to 10 percent per second maximum. If programmed to Shutdown, the engine will shut down when Very High Coolant Temperature diagnostic is triggered.

Throttle Position Sensor

The Throttle Position Sensor (TPS) eliminates the mechanical throttle and governor linkages (along with their inherent adjustments). The TPS utilizes operator lever movement and sends an electrical signal to the engine Electronic Control Module (ECM). The TPS signal, along with the speed/timing signal is processed by the ECM to control precise engine speed.

Throttle Position vs. PWM Input

Figure 1.4 - Speed Control with PWM Input

PWM Input Requirements

* Open collector sinking Pulse Width Modulated (PWM) output with pull up resistor.

* Low sensor stop 7.5 ± 2.5% and High sensor stop 92.5 ± 2.5%.

* Output frequency of 300 Hz minimum, 500 Hz nominal, 700 Hz maximum.

* Output voltage high minimum 4.0 VDC, nominal 5.0 VDC.

* Output voltage LOW nominal 0.23 VDC, maximum 0.25 VDC and 1.0mA sink current and nominal .65 VDC, maximum 0.7 VDC and 10.0 mA sink current.

* Output linearity ±2.5% (+ duty vs. throttle lever position.

Figure 1.5 - PWM Input Requirements

Load Factor Calculation

Engine Speed Limits

Figure 1.6 - Speed Limit Graph

* Programmable Low and High Speed Limits

* Isochronous Engine Governing at Part Load

High Idle Limit

Figure 1.7 - High Idle Limit Graph

* TEL programmable from 1600-2310 rpm

* Droop Programmable Using High Idle (TEL to 2310 rpm)

* Droop Active at TEL Only

* Isochronous Governing at Part Speed

Fuel Temperature Power Compensation

Figure 1.8 - Fuel Temperature Power Graph

* Provides Power at all fuel temperatures

Fuel Temperature Sensor

Fuel temperature is monitored to adjust fuel rate calculations, and for fuel temperature power correction when fuel temperatures exceed 30 °C (86 °F) to provide consistent power. Maximum power correction is achieved at 70 °C (158 °F). Fuel Temperatures exceeding 80 °C (176 °F) for 30 seconds cause a diagnostic code to be logged.

Auxiliary Pressure Sensor

The Engine Monitoring System provides an additional pressure sensor input for protection of engine driven equipment. EMS will monitor this parameter and turn on the auxiliary pressure fault light if the monitored pressure exceeds the customer programmable setting.

The Auxiliary Pressure Sensor is an analog sensor with an operating range of 0 to 2900 kPa (0 to 420 psi). Programming the set point to 0 will disable all diagnostics associated with the Auxiliary Pressure Sensor.

Schematic

Auxiliary Temperature Sensor

The Engine Monitoring System provides an additional temperature sensor input for protection of engine driven equipment. EMS will monitor this parameter and turn on the auxiliary temperature fault light if the monitored temperature exceeds the customer programmable setting.

The Auxiliary Pressure Sensor is 455 Hz digital sensor with an operating range of 0 to 120 °C (32 to 248 °F). Programming the set point to 0 will disable all diagnostics associated with the Auxiliary Temperature Sensor.

Schematic

Block Diagram

Figure 1.9 - Block Diagram

Service Tools

The Caterpillar Electronic Service Tools for the electronic control system are designed to help the service technician analyze and locate faults or problems within the system. It is required to perform some sensor calibrations electronically, and to read or change engine parameters.

The Electronic Control Analyzer Programmer (ECAP) tool has small plug-in modules, called Service Program Modules (SPM), to adapt the basic tool to the specific Caterpillar electronic control application.

Caterpillar Electronic Technician (ET) requires a personal computer with the ET software installed and a Caterpillar Communication Adapter to translate from the data link to the computer RS-232 port.

The ECAP or ET communicates with the Electronic Control Module to read diagnostic codes, to read the various sensor output signals such as engine speed, or boost pressure, and controls electronic calibration of the sensors through the ECM.

The ECAP (requires PWM adapter to measure at the sensor) can measure Pulse Width Modulated (PWM) signals, such as the signal produced by the Throttle Position Sensor.

There are several adapter cables, Breakout T cables, probes, etc, that are used with the Electronic Service Tools in order to access measurements of signals.

The Breakout T harness is inserted in series between a harness jack and plug to permit voltage measurement on an operating system. The Bypass T harness is used to bypass the harness signal lines for engine sensors

A heavy duty multimeter is suitable for making the necessary measurements. Other Special Tools include those needed to measure pressure or temperature.

Connecting ECAP Electronic Service Tool and Communication Adapter Tool

The Electronic Control Analyzer & Programmer (ECAP) and the Communications Adapter are DC powered from the engine or unit battery source.

Use the following procedures to connect the ECAP to the Service Tool data link Connector.

1. Turn the keyswitch to the OFF position.

2. Connect the Electronic Service Tool to the electronic system through the data link connector, J60 (or J42, if equipped). Connect the 139-4166 harness connector cable.

3. Connect the opposite end of the adapter cable to the Electronic Service Tool. Turn the keyswitch to the ON position to begin testing. The Electronic Service Tool will operate with the engine running (keyswitch ON) or with the engine off (keyswitch ON). If the Electronic Service Tool does not communicate with the ECM, Refer to Section 3 P-307: Electronic Service Tool Will Not Communicate With ECM.

NOTE: The Electronic Service Tool may restart during engine cranking due to a voltage dip on the battery line.

Connecting ET Electronic Service Tool and Communication Adapter Tool

ET consists of an IBM compatible computer (laptop) and software. The software allows the laptop user to program ECM parameters, read and display sensor values and switches, perform diagnostic tests and calibrate sensors. The following table outlines the tools required to use ET.

The Communication Adapter Tool uses DC power from the battery. Use the following procedure to connect ET and the Communication Adapter service tools to the engine.

1. Turn the keyswitch to the OFF position.

NOTE: If the keyswitch is not placed in the OFF position, the engine may start and run.

2. Connect the 139-4166 cable between the Engine Service Tool Connector (9-Pin, gray plastic, Deutsch) and the Communication Adapter CONTROL Connector.

3. Connect the 7X-1688 cable between the laptop RS232 serial port and the Communication Adapter SERVICE Connector.

4. Turn the keyswitch (or ECS) to the ON position, engine OFF to begin testing. This will provide Battery voltage to the ECM. ET and the Communication Adapter Tool will operate with or without the engine running. If ET and Communication Adapter Tool do not communicate with the ECM, Refer to Section 3: P-307: Electronic Service Tool Will Not Communicate With ECM.