3176B INDUSTRIAL ENGINE Caterpillar

Section 1: Electronic System Overview

Usage:

System Operations

The 3176B Industrial Engine utilizes 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 3176B Industrial Engine 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 rpm" based on the throttle signal, PTO switches (only while in PTO mode) and certain diagnostic codes. The ECM then maintains the desired engine rpm by sensing actual engine rpm and deciding how much fuel to inject in order to achieve the desired rpm.

Engine Governor

The Electronic Control on the engine serve as the engine governor. The Electronic Control determines 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 rpm and compares this to the actual engine rpm determined through the Engine Speed/Timing Sensor. If desired engine rpm is greater than the actual engine rpm, the governor injects more fuel to increase engine rpm.

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 Manifold Temperature Sensor, Atmospheric Pressure Sensor, And Inlet Manifold (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 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 rpm limit the ECM uses as a maximum rpm for fuel delivery to the injectors. The ECM will not fuel the injectors above this rpm.

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

Engine Monitoring

Caterpillar provides a factory installed Engine Monitoring System. The Caterpillar Engine Monitoring System monitors engine oil pressure, coolant temperature, inlet air manifold temperature, coolant level and fuel temperature.

The Oil Pressure, Inlet Air Manifold Temperature, Fuel Temperature, Fuel Pressure And Coolant Temperature Sensors are standard on all engines.

Caterpillar Engine Monitoring can be programmed to different modes (OFF, WARNING and DERATE and SHUTDOWN). The Coolant Temperature Sensor, Oil Pressure Sensor and Coolant Level Sensor (if enabled) will operate in the Engine Monitoring Mode selected. For example, if DERATE mode was selected, the engine will derate engine power if the Coolant Temperature Sensor, (if enabled) detect conditions exceeding acceptable limits. The Oil Pressure Sensor can NOT be programmed to WARNING, while the Coolant Temperature Sensor operates in a different mode such as DERATE.

An excessive Inlet Air Manifold Temperature will not derate or shutdown the engine. if the Engine Monitoring Mode is programmed to SHUTDOWN, and a 105-11 (Very High Inlet Air Manifold Temperature) Diagnostic code is ACTIVE, the engine will WARN but will not DERATE or SHUTDOWN.

Caterpillar Engine Monitoring OFF Operation

If Caterpillar Engine Monitoring is programmed to OFF, the ECM will not flag any of the sensor values and disables those diagnostics associated with Engine Monitoring even though the level or conditions are exceeded which could cause the ECM to take Engine Monitoring action. The ECM still uses these sensors for normal engine operation, such as the Coolant Temperature Sensor for Cold Mode operation. The Warning Lamp should not operate and is unnecessary.

Caterpillar Engine Monitoring WARNING Operation

If the system is programmed to WARNING, the ECM commands the Warning Lamp to turn ON and log the event to indicate a problem has been detected by the Engine Monitoring System. No further ECM or engine action occurs if the ECM is programmed to WARNING.

NOTE: The Oil Pressure Sensor can not be programmed to WARNING, while the Coolant Temperature Sensor operates in a DERATE Mode.

Caterpillar Engine Monitoring DERATE Operation

If the system is programmed to DERATE, the ECM begins by flashing or activating the Warning Lamp ON. If the problem is due to a 100-01 Low Oil Pressure Warning and 111-01 Low Coolant Level Warning will cause the Warning Lamp to ON (solid, not flashing). Conditions causing Diagnostic Codes 110-00 High Coolant Temperature, 110-11 Very High Coolant Temperature, 100-11 Very Low Oil Pressure and 111-11 Low Coolant Level Warning will cause the Warning Lamp to FLASH. The Warning Lamp flashes whenever the engine is derated. During DERATE mode the Warning Lamp will begin to Pulse (the diagnostic check engine lamp will flash indicated the presence of an Active diagnostic code), and the available engine power and speed will be limited (if due to Very Low Oil Pressure, engine speed is also limited. This derating of engine performance is provided to the operators so action can be taken to avoid engine damage.

Caterpillar Engine Monitoring SHUTDOWN Operation

If the system is programmed to SHUTDOWN, the ECM will indicated diagnostic codes are active through the Check Engine lamp. Conditions causing diagnostic codes 100-01, Low Oil Pressure Warning and 111-01 Low Coolant Level Warning will cause the Warning lamp to illuminate. Conditions causing the diagnostic Codes 110-00 High Coolant Temperature, 110-11 Very High Coolant Temperature, 100-11 Very Low Oil Pressure and 111-11 Very Low Coolant Level will cause the Warning Lamp to begin to FLASH (indicating DERATE). If conditions causing Diagnostic Codes 110-11 Very High Coolant Temperature, 100-11 Very Low Oil Pressure and 11-11 Very Low Coolant level continue, the engine will eventually shut down.

Self-Diagnostics

The electronic system has some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and the Diagnostic/Check Engine lamp is turned ON. 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 the front of this manual and proceed to the appropriate Functional Test 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 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.

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 3176B Industrial). Once activated, cold Mode will continue until coolant temperature rises above 28°C (82°F), or until the engine has been running for 12 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 Cruise/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.

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. This means 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.

When the ECM detects a loss of the Unswitched +Battery connection it automatically increments the memory dependent upon the Unswitched +Battery connection to one-half of the value that could be lost. This reduces the margin of error from a maximum of 2 hours to 1 hour and 150 to 75 liters (40 to 20 US gallons).

This also means disconnecting the Unswitched +Battery line can actually increase these Totals. If the value in the Unswitched +Battery memory before disconnection was less than the automatic increment the total will be increased. If an ECM is replaced the Data Totals can be transferred to the new ECM using an Electronic Service Tool.

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 with an Electronic Service Tool. The data is stored in memory maintained through the Unswitched +Battery connection when the keyswitch is OFF. Disconnecting 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. A reset of the Histograms can be done with an Electronic Service Tool (may require Customer Passwords).

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 3176B Industrial 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 cruise control, 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.

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. The customer passwords are programmed by the customer.

See section Section 2: Programming Parameters for more details when passwords are needed and how to obtain them.

Indicator Lamps

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.

Check Engine/Diagnostic Lamp

The Check Engine Lamp is used to indicate the existence of a diagnostic code, to indicate "operator alert" status of the Idle Shutdown Timer, and may be used to read Flash Codes. While the engine is operating, it will illuminate for a minimum of five seconds at a time a fault condition exists. It will continue to flash ON for five seconds, and then blink OFF, flash ON for five seconds, etc, as long as the fault condition exists. On power up (keyswitch ON, engine OFF), the lamp will illuminate for five seconds. It will continue to Flash if there is an Active Diagnostic Code. Active Diagnostic Flash Codes may be flashed out at any time by turning the cruise ON/OFF switch to OFF, and holding the SET/RESUME switch in either the SET or RESUME position until the lamp begins to flash, then releasing it. The Flash Code is determined from the number of times the Check Engine Lamp blinks. The lamp will blink for the first digit of the flash code, pause five seconds, and then blink for the second digit. The Flash codes are two digit representation of diagnostic codes. Flash Codes should only be used for a general idea of a problem and not for explicit troubleshooting.

NOTE: If the Check Engine/Diagnostic Lamp continually flashes diagnostic flash codes (without operator prompting) the SET/RESUME circuits are most likely short circulated to ground.

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 will not illuminate with the keyswitch in the ON position, Engine 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.

Electronic Control System Overview

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, pin-1 (ATA Data Link -) and pin-7 (ATA Data Link). The machine OEM is responsible for providing twisted pair wiring form the ECM to the Data Link Connector.

NOTE: The ECM does not provide the power and ground 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.

Auxiliary Sensors

A customer installed Auxiliary Pressure, and Auxiliary Temperature sensor allows the ECM to monitor auxiliary pressure. This sensor provides a pulse with modulated signal at 500 Hz. Pressure (kPa Absolute) equals the percent duty cycle minus 9.708 multiplied by 44.727.

Cooling Fan Relay

The Cooling fan Relay signal is provided by the ECM to control the ECM Cooling Fan using inputs from the Engine Coolant Temperature Sensor, Retarder Solenoid and an optional OEM installed A/C High Pressure Switch. Operation of the fan can also be controlled independently of the ECM by OEM installed components such as an A/C High Pressure Switch (when not connected directly to the ECM). The circuit is set up to provided a 12 V signal to turn the fan OFF. Once the ECM has turned the fan ON, the fan will remain ON for a minimum of 30 seconds to avoid unnecessary fan clutch cycling (except at engine start up, it will run for only 2 seconds after the engine starts.

The ECM Cooling Fan Relay is intended to power a relay with normally open contacts so the ECM will close the circuit (energize the relay) to turn the fan OFF. This means the fan will be ON all the time if the electrical circuit to the cooling fan air solenoid valve is opened or the ECM Cooling Fan Relay circuit is opened.

The Cooling Fan Relay is not energized to turn the fan ON under the following conditions:

If the engine speed is < 2250 rpm or the Engine is not running AND ANY OF THE FOLLOWING CONDITIONS EXISTS.

* Coolant Temperature > 96°C (205°F) OR...

* Active Coolant Temperature Sensor Diagnostic Code OR...

* Retarder solenoids Active in High Mode > 10 seconds with Coolant Temper Sensor > 80°C (176°F) OR...

* A/C High Pressure Switch Fan ON time programmed to 30 to 600 seconds with an open circuit condition on the A/C High Pressure Switch OR...

* 228-03 A/C High Pressure Switch Open Circuit OR...

* The Inlet Air Manifold Temperature is > 87°C or the Inlet Air Manifold Temperature is > 72°C and Boost Pressure is > 70 kPa.

The Cooling Fan Relay is energized to turn the fan OFF under the following conditions.

* Engine Speed > 2300 rpm

OR ALL OF THE FOLLOWING CONDITIONS EXIST:

* Coolant Temperature Sensor < 92°c (198°F) And...

* Not Active Coolant Temper Sensor Diagnostic Code AND...

* Retarder Solenoids Active in High mode with Coolant Temp Sensor > 75°C (167°F) AND.

* A/C High Pressure Switch is CLOSED and the ECM is not counting. (or A/C is programmed to 0 sec). The engine has been running for at least 2 seconds. AND...

* Inlet Manifold Temperature is < 66°C (140°F).

The ECM Cooling Fan Relay is controlled by the Coolant Temperature Sensor, combined with the Retarder Solenoids, or (optional) OEM installed A/C High Pressure Switch.

Before troubleshooting the Cooling Fan Relay circuit determine the failure mode. if the problem is related to the fan always OFF, then the problem is most likely in the OEM air solenoid valve to air system, and not an electrical system. If the problem is with the fan always ON, it is most likely due to a wiring open circuit or a switch stuck in the open circuit position.

* OEM installed Components affecting the cooling Fan operation typical applications are:

* OEM installed, normally closed relay

* An A/C High Pressure Switch (either connected to the ECM or independent of the ECM)

* A timer (to keep fan ON for a minimum time.)

* Cooling Fan Solenoid Air Valve

The components should be connected in series with the contact side of the relay to machine battery and the Cooling Fan Solenoid air valve.

NOTE: the ECM does not read the OEM installed device (except for the optional A/C High Pressure Switch) to determine Cooling Fan Relay operation. the OEM installed Cooling Fan components determine the path of the signal, because they are switches and may interrupt power to the Cooling Fan Solenoids, Activating the Fan.

The Cooling Fan Relay Signal current should be less than 0.2 Amp DC to indicate the fan should be ON and 0.2 to 1.0 Amps DC to indicate the ECM would like to turn the fan OFF. The remainder of the engine cooling circuit is supplied by the OEM.

To determine if a machine is using the ECM Cooling Fan Circuit to control the Cooling Fan, use the Electronic Service Tool "Special Test" Cooling Fan Driver Test. Making the circuit Active and then Not Active should cause the air solenoid to click if the circuit is working properly. If it is not working you must physically inspect the machine for the wiring and relay connection to the ECM. Your cannot use the ET status screen or review any Customer Parameter to determine for certain if the machine is using the ECM Cooling Fan Circuit Test.

Inlet Manifold Heater Relay

The Caterpillar Inlet Manifold Heater, or Flammstart is an option available for cold and high altitude applications. A heater plug in the inlet manifold preheats the engine and during cranking diesel fuel is directed onto the heater plug which mixes with air and ignites. The air is now heated before entering the inlet manifold. The fuel is tuned off after a predetermined duration expires.

Flammstart

The flammstart is a separate system that may operate independent of the engine control. However, to optimize the cold start strategy may be desired to turn off fuel injection to heater plug before the flammstart system normally would. With the Flammstart relay connected, the ECM will disable the Flammstart after inlet air reaches 55°C. This reduces the chance of the flame becoming counterproductive as it consumes oxygen. For more information on Flammstart, refer to SEHS9551, Inlet Manifold Heater Operation Manual. The Inlet Manifold will turn off if the engine speed is < 500 rpm and the Inlet Air Temperature is < 55°C (131°F).

Fuel Temperature Sensor

The Fuel Temperature Sensor monitors the fuel temperature and is used by the ECM to adjust the ECM calculated fuel rate. The ECM compensates for temperature changes and adjusts the actual fuel rate for fuel temperature above 30°C (86°F). The sensor is also used to warn the operator of an excessive fuel temperature. The Fuel Temperature Sensor operates independently of Caterpillar Engine Monitoring. If Engine Monitoring is programmed to OFF, the Fuel Temperature Sensor is not ignored or affected. The sensor operates on +5 VDC supplied through pin-36 of the ECM connector J2/P2.

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 sensor operates on +5 VDC supplied through pin-36 of the ECM connector J2/P2.

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. The sensor operates on +5 VDC supplied through pin-36 of the ECM connector J2/P2.

Tachometer

The Tachometer consists of the Tachometer connected to the ECM by connector P1/J1 and associated wiring. The ECM engine speed signal is provided by the Engine Speed/Timing Sensor into engine speed scaled at customer programmed pulses per revolution (ppr) before sending out to the Tachometer. The selection of the ppr for the Tachometer is done through a Customer Programmable Parameter, Tachometer Calibration.

NOTE: The ECM tachometer signal is set to 113 pulses per revolution at the factory. All tachometers driven from the ECM must be between 12 and 500 ppr. The most likely source of a tachometer problem is the wiring, then the tachometer itself and least likely the ECM. Do not disturb the Engine Speed/Timing Sensor to troubleshoot a tachometer problem. If there is a problem associated with the Speed/Timing Sensor Refer To Section 5: P-514 Engine Speed/Timing Sensor. Any problem associated with the Engine Speed/Timing Sensor would be more apparent than a Tachometer problem to engine operation.

Inlet Air Manifold Temperature Sensor

The Inlet Air Manifold Temperature Sensor measures 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. The Inlet Air Manifold Temperature Sensor does not affect Cold Mode low idle engine rpm like the Coolant Temperature Sensor. The sensor operates on +5 VDC supplied through pin-36 of the ECM connector J2/P2.

Inlet Air Manifold Pressure

The ECM monitors Inlet Air Manifold 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 Inlet Air Manifold 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 Inlet Air Manifold Pressure Sensor can measure pressure from 20 kPa (3 psi) to 340 kPa (49 psi). The sensor operates on +5 VDC supplied through pin-36 of the ECM connector J2/P2.

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. The sensor operates on +5 VDC supplied through pin-36 of the ECM connector J2/P2.

3176B EUI Electronic Governor

Figure 1.2 - EUI Electronic System Diagram

3176B Industrial Engine Block Diagram

Figure 1.3 - 3176B Block Diagram

Computerized Monitoring System

The Computerized Monitoring System (CMS) is an electronic monitoring system used to display engine/transmission operating information. The System Diagnostic indicators (on the right side of the display panel) identify present conditions. If an indicator illuminates, refer to the procedure indicated below to troubleshoot the condition.

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 the data link to the computer RS-232 protocol.

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

The ECAP 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 to 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 7X1688 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.