3126E On-highway Engine Caterpillar

System Operation

The engines use a Hydraulic Electronic Unit Injector fuel system. The injection pump, the fuel lines and the nozzles that are used in mechanical engines have been replaced with an hydraulic electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel that is delivered by the injector. A axial piston pump increases the engine oil pressure in order to activate the injector. An Engine Control Module (ECM) sends a signal to the injection actuation pressure control valve in order to control injection pressure. Another electrical signal is sent to each injector solenoid in order to inject fuel.

Electronic Controls

The engine's electronic system consists of the Engine Control Module (ECM), the engine sensors, the injection actuation pressure control valve, and the vehicle interface. The ECM is the computer. The personality module is the software for the computer. The personality module contains the operating maps. The operating maps define the following characteristics of the engine:

• Horsepower

• Torque curves

• Engine speed (rpm)

Engine Governor

The electronic controls on the engine serve as the engine governor.

The electronic controls determine the timing, the injection pressure and the amount of fuel that is delivered to the cylinders. These decisions are based on the actual conditions and the desired conditions at any given time during starting and operation.

The governor uses the accelerator pedal position sensor to determine the desired engine speed. The governor compares the desired engine speed to the actual engine speed. The actual engine speed is determined through the camshaft position sensors. If the desired engine speed is greater than the actual engine speed, the governor injects more fuel in order to increase engine speed.

Illustration 1	g00738860
Typical example

The desired engine speed is typically determined by one of the following conditions:

• The position of the accelerator pedal

• The desired vehicle speed in cruise control

• The desired engine rpm in PTO control

Timing Considerations

Once the governor has determined the amount of fuel that is required, the governor must determine the timing of the fuel injection. Fuel injection timing is determined by the ECM after considering input from the following components:

• Coolant temperature sensor

• Intake manifold air temperature sensor

• Atmospheric pressure sensor

• Boost pressure sensor

The ECM knows the cylinder position for timing because of the signal from the engine speed/timing sensors. The ECM adjusts timing for best engine performance, for fuel economy, and for the control of white smoke. Actual timing and desired timing cannot be viewed on the Caterpillar Electronic Technician (Cat ET). The ECM determines the location of top center of the number one cylinder from the signal that is provided by the engine speed/timing sensors. The ECM decides when injection should occur relative to top center. The ECM then provides the signal to the injector at the desired time.

Illustration 2	g00693339

Fuel Injection

The ECM controls the amount of fuel that is injected by varying the signals to the injectors and by controlling actuation pressure. The injectors will pump fuel only if the injector solenoid is energized. The ECM sends a high voltage signal in order to energize the solenoid. The injector solenoid moves a seated pin that allows the actuation pressure to hold the nozzle check closed. The movement of the seated pin also causes the spool valve to open. This allows the actuation pressure to act on the piston and on the plunger. This produces injection pressure. The hydraulic force that holds the nozzle check closed quickly dissipates and the injection pressure opens the nozzle check. By controlling the timing and the duration of the high voltage signal, the ECM can control the following aspects of injection:

• Injection timing

• Fuel delivery

• Injection rate shape

The ECM controls injection pressure by controlling the injection actuation pressure control valve (IAPCV). The IAPCV controls the pump outlet pressure by moving components within the pump.

The personality module inside the ECM sets certain limits on the amount of fuel that can be injected. The "FRC Fuel Limit" is a limit that is based on the boost pressure. The "FRC Fuel Limit" is used to control the air/fuel ratio for control of emissions. When the ECM senses a higher boost pressure, the ECM increases the "FRC Fuel Limit". A higher boost pressure indicates that there is more air in the cylinder. When the ECM increases the "FRC Fuel Limit", the ECM allows more fuel into the cylinder.

The "Rated Fuel Limit" is a limit that is based on the power rating of the engine and engine rpm. The "Rated Fuel Limit" is similar to the rack stops and the torque spring on a mechanically governed engine. The "Rated Fuel Limit" provides the power curves and the torque curves for a specific engine family and a specific engine rating. All of these limits are determined at the factory. These limits are in the personality module and these limits cannot be changed.

Injection Actuation Pressure Control System

The ECM controls the fuel injection delivery and injection pressure by controlling oil pressure to the fuel injectors. The pressure of the oil in the high pressure oil manifold is controlled by the ECM through control of the injection actuation pressure control valve. The injection actuation pressure control valve regulates the pump outlet pressure.

The ECM monitors the pressure in the high pressure manifold through the injection actuation pressure sensor. The injection actuation pressure sensor is located in the top of the manifold on the left side of the engine. The injection actuation pressure sensor's signal is compared by the ECM to the desired injection actuation pressure. The injection actuation pressure sensor's signal is based on sensor inputs. The sensor inputs are used to adjust the control current to the injection actuation pressure control valve in order to adjust the oil pressure in the high pressure manifold.

High pressure oil is routed from the pump to the high pressure manifold through a steel tube. From the manifold, the oil is routed to each injector through the high pressure oil manifold. All injectors have a constant supply of oil while the engine is running. Disabling the electrical signal to the injector solenoid does not interrupt the oil flow that is available to the fuel injector.

Cold Mode

Cold Mode is activated when the coolant temperature is below 18 °C (64 °F). When Cold Mode begins, the idle rpm speed ramps up to 1000 rpm unless another value has been programmed into the "Warm Up Mode Idle Speed" parameter. Cold Mode stays active until any of the following conditions are met:

• The coolant temperature reaches 18 °C (64 °F).

• 12 minutes have expired.

• The service brake is depressed.

• The clutch pedal is depressed.

• The automatic transmission is placed in gear.

Customer Parameters and Engine Speed Governing

A unique feature with electronic engines is Customer Specified Parameters. These parameters allow the vehicle owner to fine tune the ECM for engine operation. Fine tuning the ECM for engine operation allows the vehicle owner to accommodate the typical usage of the vehicle and the power train of the vehicle.

Many of the customer parameters provide additional restrictions on the actions that will be performed by the ECM in response to the driver's input. For example, the "PTO Top Engine Limit" is an engine rpm limit. The "PTO Top Engine Limit" is an engine rpm limit that is used by the ECM as a cutoff for the fuel. The ECM will not fuel the injectors above this rpm.

Some parameters are intended to notify the driver of potential engine damage (Engine Monitoring Parameters). Some parameters enhance fuel economy (Vehicle Speed, Cruise Control, Engine/Gear Speed Limit Parameter and Idle Shutdown). Other parameters are used to enhance the engine installation into the vehicle. Other parameters are also used to provide engine operating information to the truck engine owner.

Engine Monitoring

Caterpillar provides a factory installed Engine Monitoring System. The Caterpillar Engine Monitoring System monitors engine oil pressure, coolant temperature, intake manifold air temperature, and coolant level (optional device). Optional devices are OEM installed.

The oil pressure, intake manifold air temperature, and coolant temperature sensors are standard on all engines. The vehicle OEM installs the coolant level sensor and the associated harness. The coolant level sensor is the only optional component of Caterpillar Engine Monitoring. Coolant level is selected through a Customer Programmable Parameter.

Caterpillar Engine Monitoring can be programmed to three different modes. These three modes of programming are the following modes: "WARNING", "DERATE" and "SHUTDOWN". The coolant temperature sensor, the oil pressure sensor and the coolant level sensor (optional device) will operate in the Engine Monitoring Mode that is selected.

For example, if Derate Mode was selected, the engine will derate engine power and vehicle speed. The engine will derate engine power and vehicle speed if the coolant temperature sensor, the oil pressure sensor or the coolant level sensor detects conditions that exceed acceptable limits.

An excessive intake manifold air temperature will not derate the engine. Also, an excessive intake manifold air temperature will not shut down the engine.

Caterpillar Engine Monitoring

"WARNING" Operation

If Caterpillar Engine Monitoring is programmed to "WARNING", the ECM will illuminate the warning lamp and the ECM will flash the check engine lamp because of the active diagnostic code. The flashing lamp indicates that a problem has been detected by the engine monitoring system. The diagnostic code is logged. No further action by the ECM or action by the engine occurs if the ECM is programmed to "WARNING".

"DERATE" Operation

If the system is programmed to "DERATE", the ECM begins by flashing the check engine lamp and the Warning lamp. The flashing lamps indicate that a problem has been detected by the engine monitoring system. The diagnostic code is logged. High coolant temperature will signal the ECM to limit the maximum vehicle speed and the ECM will reduce the engine power rating. Refer to Illustration 3 and Illustration 4.

Illustration 3	g00694414
Coolant temperature bargraph Derate mode is limited. (10% per second)

Illustration 4	g00694655
Coolant temperature bargraph for emergency vehicles Derate mode is limited. (10% per second)

Low coolant level will signal the ECM to limit the maximum vehicle speed and the ECM will reduce the engine power rating. Refer to Illustration 5.

Illustration 5	g00821752
Graph for the coolant level Derate mode is limited. (10% per second)

Very low oil pressure will signal the ECM to limit the maximum vehicle speed and the ECM will reduce the engine power rating. Refer to Illustration 6.

Illustration 6	g00821786
Graph for very low oil pressure

This derating of engine performance is provided in order to get the driver's attention so the driver can take action in order to avoid engine damage.

"SHUTDOWN" Operation

If the system is programmed to "SHUTDOWN", the ECM takes all the action that is indicated for the "DERATE" mode and the ECM will eventually shut down the engine under some conditions.

The "SHUTDOWN" mode begins when any of the following conditions exist:

• "Very low oil pressure"

• "Very low coolant level"

• "Very high coolant temperature"

"SHUTDOWN" mode begins by flashing the warning lamp. This response is similar to the response when the system is in "DERATE". "SHUTDOWN" mode will eventually shut down the engine if the conditions continue for a long enough time and the conditions are severe enough. The engine can be restarted as many times as needed after an engine shutdown. This allows the vehicle to be pulled off of the road.

Other ECM Functions Of Performance

The ECM also provides enhanced control of the engine for vehicle functions such as retarding the engine and controlling the cooling fan. Refer to Troubleshooting, "Customer Specified Parameters" for supplemental information about the systems that can be monitored by the ECM in order to provide enhanced vehicle performance, fuel economy and convenience for the driver.

Self-Diagnostics

The electronic system has the ability to diagnose problems. When a problem is detected, a diagnostic code is generated and the check engine/diagnostic lamp may be turned on. In most cases, the code is also stored in permanent memory or logged in the Engine Control Module (ECM).

When diagnostic codes occur, the diagnostic codes are called active diagnostic codes. Active diagnostic codes indicate that a problem of some kind currently exists. Active diagnostic codes should always be serviced before any other work is performed. If a truck is brought in with an active code, find the code in this manual and proceed to diagnose the cause.

Diagnostic codes that are stored in memory are called logged diagnostic codes. Logged diagnostic codes do not necessarily indicate that something needs to be repaired. The problem may have been temporary, or the problem may have been repaired since the problem was logged. Logged diagnostic codes are instead meant to be an indication of probable causes for intermittent problems.

Diagnostic codes that identify operating conditions outside the normal operating range are called events. Event codes are not typically an indication of an electronic system problem.

Some of the diagnostic codes require passwords to be cleared from memory. Diagnostic codes that do not require passwords to be cleared from memory are automatically deleted after 100 hours of engine operation.

Engine Snapshot Data

Whenever most diagnostic codes occur, the ECM records the time in engine hours of the occurrence. Also, the ECM records the operating parameters of the engine for 9 seconds before the diagnostic code and 3 seconds after the diagnostic code. The operating parameters of the engine that are recorded are similar to the operating parameters of the engine that are displayed in the status screens of the Electronic Technician. Not all of the status screens of the Electronic Technician or parameters are recorded. The Engine Snapshot can also be triggered from the Cruise Control Set/Resume switch. In order to trigger the Engine Snapshot from the Cruise Control Set/Resume switch, quickly toggle the switch to the Set position. Then, quickly toggle the switch to the Resume position. You can also toggle the Cruise Control Set/Resume switch from the Resume position to the Set position. The Engine Snapshot can also be triggered from the Electronic Technician.

Effect Of Diagnostic Codes On Engine Performance

The discussion on Engine Monitoring mentions that the check engine lamp flashes when a specific condition exists. When the ECM detects the engine problem, the ECM generates an active diagnostic code. Also, the ECM Logs the diagnostic code in order to indicate the time of the problem's occurrence. The ECM also Logs the number of occurrences of the problem.

Diagnostic Codes

Diagnostic codes are provided in order to indicate that an electrical problem or an electronic problem has been detected by the ECM. In some cases, the engine performance can be affected when the condition that is causing the code exists. More frequently, the driver cannot detect any difference in the engine performance.

If the check engine lamp is flashing and the driver indicates that a performance problem occurs, the diagnostic code may indicate the cause of the problem. The problem should be corrected.

If the driver does not indicate a problem with the engine performance and a diagnostic code is logged by the ECM, the situation indicates that the ECM detected an abnormal condition, but the abnormal condition did not affect engine performance.

In this situation, the system has no faults except when either of the following conditions exist:

• There are several occurrences of the diagnostic code in a very short period of time.

• The ECM is indicating an active code at the present time.

Diagnostic Event Codes

Diagnostic event codes are used to indicate that some operational problem has been detected in the engine or in the truck by the ECM. Usually, this does not indicate an electronic malfunction.

The ECM also provides an ECM date/time clock that is used to time stamp the following diagnostic event codes:

• 84-00 Vehicle Overspeed Warning (41)

• 100-11 Very Low Oil Pressure (46)

• 105-11 Very High Intake Manifold Air Temperature (64)

• 110-11 Very High Coolant Temperature (61)

• 111-11 Very Low Coolant Level (62)

• 190-00 Engine Overspeed Warning (35)

ECM Lifetime Totals

The ECM maintains total data of the engine for the following parameters:

• "Total Time" (Engine Hours)

• "Total Distance"

• "PTO Time" and "PTO Fuel"

• "Idle Time" and "Idle Fuel"

• "Average Load Factor "(Engine)

• "Total Fuel"

• "Total Max Fuel"

The "Total Time" is the engine's operating hours. The operating hours do not include the operating time when the ECM is powered but the engine is not running.

"Total Distance" data requires a vehicle speed sensor or an electronic vehicle speed source to be connected to the ECM. The same sensor is used for vehicle speed. Distance can be displayed in miles or kilometers.

"PTO Time" and "PTO Fuel" are logged when engine rpm is set by using the Cruise switches and the engine is operating under some load. Also, "PTO Time" and "PTO Fuel" are logged when the PTO On/Off Switch is in the ON position and vehicle speed is within the range of the "PTO Vehicle Speed Limit" parameter.

"Idle Time" and "Idle Fuel" can include operating time when all of the following conditions are met:

• When engine speed is set by using the cruise switches and the vehicle speed is within the range of the "Idle Vehicle Speed Limit" parameter.

• The engine is not operating under a load.

Fuel Information can be displayed in US gallons or liters.

"Total Fuel" is the total amount of fuel that is consumed by the engine during operation.

"Total Max Fuel" is the maximum amount of fuel that could have been consumed by the engine during operation.

"Average Load Factor" provides relative engine operating information. "Average Load Factor" compares actual operating information of the engine to the maximum engine operation that is available. "Average Load Factor" is determined by using "Total Max Fuel", "Idle Fuel", and "Total Fuel". All of these parameters are available by using Cat ET. These parameters are available within the menu for "Current Totals".

Trip Data That Is Stored In The ECM

The Trip Data allows the tracking of engine operation by the vehicle owner over intervals that are defined by the vehicle owner. All of the Trip Data is stored in memory and the Trip Data is maintained through the unswitched battery lines when the ignition switch is OFF. An internal battery will maintain this information while the unswitched battery lines are disconnected.

Fleet Trip Data

Fleet Trip Data includes Histograms and Custom Data. The Fleet Trip Data includes data for the following parameters:

• "Total Time"

• "Driving Time"

• "Distance"

• "Fuel"

• "Idle Time"

• "Idle Fuel"

• "PTO Time"

• "PTO Fuel"

• "Percent PTO Time"

• "Average Load Factor"

• "Average Vehicle Speed"

• "Average Driving Speed"

• "Maximum Vehicle Speed"

• "Maximum Engine Speed"

• "Start Time"

• "End Time"

• "Start Odometer"

• "End Odometer"

Three histograms are available. One histogram records engine hours versus the engine speed. The second histogram records engine hours versus vehicle speed. The third histogram records engine hours versus engine speed and vehicle speed.

Cat ET calculates the percentage of time that is spent in each of the engine rpm or vehicle speed ranges. Custom Data is available. Custom Data allows the recording of engine parameters that are specified by the vehicle owner. The ECM records the Custom Data.

A reset of the Fleet Trip Data which includes the Fleet Trip Segment, the Histograms, and the Custom Data can be done in several ways. The following tools can be used to reset the Fleet Trip Data:

• Cat ET which may require Customer Passwords

• Caterpillar Fleet Information Software (FIS)

• CAT ID which requires programming of the Customer Parameters to provide access

When the data is reset, the ECM records the Current Totals at the time of the reset. These Totals are used as the starting point for the Fleet Trip. The following tools access the recorded starting point:

• Cat ET

• Caterpillar Fleet Information Software (FIS)

• CAT ID

The tool then subtracts the recorded starting point from the Current Totals in the ECM in order to calculate the Fleet Trip Data. Resetting the Fleet Trip Data requires Customer passwords if the passwords are programmed.

Maintenance Indicator Data

The ECM records the Current Totals when a reset occurs for the following three levels of maintenance:

• PM1

• PM2

• Cooling system clean/flush

The ECM uses the previous point of maintenance in order to calculate the timing of the next scheduled maintenance work.

The "Maintenance Indicator Mode" is programmable to "Hours" or "Distance". The "PM1 Maintenance" is programmable to the "Off", "Automatic Distance", "Automatic Hours", "Manual Distance", or "Manual Hours" setting.

If the PM1 is programmed to the automatic mode, the ECM calculates the next point of maintenance by considering the history of the vehicle's operation from the previous maintenance interval. If the vehicle has a history of poor fuel economy the maintenance indicator parameter will occur sooner than a vehicle with better fuel economy.

The ECM also uses the engine oil capacity. A larger engine oil capacity provides a longer maintenance interval. The engine oil capacity is programmed into the ECM in liters or quarts. If the PM1 is programmed to the manual mode, the owner can program the ECM in the owner's specific maintenance interval. The maintenance interval can be programmed to the owner's specific interval that is based on mileage or time. The interval for the PM2 and the interval for the cooling system clean/flush are established by the factory.

CAT ID

The Caterpillar Driver Information Display (CAT ID) is available to provide engine operating information to the driver. The "Fleet Trip Data", and the "Maintenance Indicator" data can be viewed. However, the fleet trip histograms and the custom data cannot be viewed from the display.

The CAT ID provides the ability to enter an ID code for a driver in order to divide the "Fleet Trip Data" for two drivers. If the driver enters the information regarding the state of travel, the "Fleet Trip Data" can be tagged by the state of travel.

The CAT ID can be used in order to tag portions of the "Fleet Trip Data" into two ID codes. The CAT ID can also be used in order to tag portions of the "Fleet Trip Data" into the state of travel. The ID code and the information regarding the state of travel cannot be viewed from the display. Only the Caterpillar Fleet Information Software (FIS) can view this information. The ability to reset any of these parameters is dependent on customer parameters in the ECM.

The CAT ID will also display operating information such as engine rpm, coolant temperature, boost pressure, etc.

The CAT ID will also display engine diagnostic codes with the PID-FMI Diagnostic Codes. The CAT ID will also display a brief text description of the diagnostic codes.

An available feature of the CAT ID is the Theft Deterrent. The Theft Deterrent allows the driver to input a password prior to shutdown. The Theft Deterrent will prevent the engine from restarting until the password is successfully entered. The CAT ID must have the version of software that is capable of supporting this feature.

The parameter "Theft Deterrent System Control" can be programmed to "Auto-Enable". If this option is selected, the theft deterrent will automatically be activated when the engine is shut down. The driver must input the correct password in order to start the engine. This requires a CAT ID with a 2.1 or newer "EPROM".

Fleet Information Software (FIS)

The Caterpillar Fleet Information Software (FIS) is another method that can be used to review the trip information. The entire "Fleet Trip Segment", which includes the following elements of data can be accessed with the Caterpillar FIS:

• Histograms

• Custom data

• Information that is tagged by the ID code

• Information that is tagged by the state of travel

Maintenance Indicator information can also be accessed by using the Caterpillar FIS.

When the Caterpillar FIS downloads the information, the Caterpillar FIS also resets the ECM in order to prepare the ECM for the next trip. The information can be downloaded to a computer with the Caterpillar FIS program, or the information can be downloaded to an Argo Mobile Data Tool (MDT). The Argo Mobile Data Tool (MDT) is then connected to a computer in order to download the information.

Programmable Parameters

Certain parameters that affect engine operation may be changed with Cat ET. The parameters are stored in the ECM, and the parameters 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. System Configuration Parameters affect emissions or power ratings within an engine family. Factory Passwords must be obtained and factory Passwords must be used to change the System Configuration Parameters.

Customer Parameters are variable. Customer Parameters can be used to affect the following characteristics of the engine within the limits that are set by the factory, Caterpillar Engine Monitoring, and PTO operation:

• Cruise control

• Vehicle speed limits

• Progressive shifting

• Rpm ratings

• Power ratings

Customer Passwords may be required to change Customer Specified Parameters.

Some of the parameters may affect engine operation in an unusual way. A driver might not expect this type of effect. Without adequate training, these parameters may lead to power complaints or performance complaints even though the engine's performance is to the specification.

Refer to Troubleshooting, "Customer Specified Parameters".

Passwords

System Configuration Parameters are protected by Factory Passwords. Factory passwords are calculated on a computer system that is available only to Caterpillar dealers. Since factory passwords contain alphabetic characters, only Cat ET may change System Configuration Parameters. System Configuration Parameters affect the power rating family or emissions.

Customer Parameters can be protected by Customer Passwords. The Customer Passwords are programmed by the customer. Factory Passwords can be used to change Customer Passwords if Customer Passwords are lost.

Refer to Troubleshooting, "Customer Passwords" and Troubleshooting, "Factory Passwords".