3406E Truck Engines Caterpillar

Illustration 1	g00451548
The left side of the components of the electronic control system is shown. (1) Engine speed/timing sensor (2) Engine speed/timing sensor P9/J9 connector (3) Fuel temperature sensor P23. (4) Atmospheric pressure sensor connector P22/J22 (5) Sensor for the inlet manifold air temperature (6) Injector connector J5/P5 (7) Boost pressure sensor (8) Ground point for the OEM (9) Sensor for the inlet manifold pressure J3/P3 (10) Engine control module P2 (11) ECM connector J2/P2 that is for the engine (12) ECM connector J1/P1 that is for the OEM (13) Inlet air temperature sensor (14) Vehicle speed/TC probe connector J24/P24

Illustration 2	g00451551
The right side of the components of the electronic control system is shown. (15) Oil pressure sensor connector P17/J17. (16) Coolant temperature sensor P10/J10.

Engine Monitoring

The electronic control system includes Engine Monitoring. The system monitors engine oil pressure, coolant temperature, inlet manifold air temperature and coolant level. All truck engines are shipped from the factory with the following sensors: oil pressure sensor, coolant temperature sensor and inlet manifold air temperature. The OEM is responsible for providing and installing the coolant level sensor. The coolant level sensor is the only sensor that can be individually selected for Engine Monitoring. The ECM Customer Programmable Parameter enables the coolant level sensor. The default factory setting is enabled. The ECM Customer Programmable Parameters have four modes that are for Engine Monitoring:

• Off Mode

• Warning Mode (Factory Default)

• Derate Mode

• Shutdown Mode

Off Mode

The ECM will ignore the oil pressure sensor and the coolant level sensor. Coolant Temperature is still used for Cold Mode. Inlet Manifold Air Temperature is used for operation in cold air regardless of the engine monitoring mode.

Warning Mode

Warning mode uses the following sensors: Oil Pressure, Coolant Temperature, Inlet Manifold Temperature and Coolant Level. Table 1 indicates the diagnostic codes that are available. The table also shows the effect on engine performance when the diagnostic code is active. When a diagnostic code is active, the Check Engine Lamp will flash and the Warning Lamp will come on.

Derate Mode and Shutdown Mode

Derate mode and Shutdown mode allows the ECM to alter engine performance. Derate mode and Shutdown mode helps the engine avoid damage. The engine should return to normal conditions. When the engine is derated, the Check Engine Lamp and the Warning Lamp will flash. Refer to Table 2. In the Derate column, MPH indicates that the vehicle speed is derated. The maximum derate is 45 mph. HP indicates that the engine horsepower is limited. The maximum derate is 160 hp. RPM indicates that the engine speed is limited. The maximum derate is 1350 rpm. For the operating conditions that cause these codes, refer to the appropriate section for the sensor.

Time to Shutdown

Table 3 indicates the active diagnostic codes that are capable of shutting down the engine when the ECM is programmed to Shutdown. The "Time To Shutdown" column indicates the length of time until engine shutdown will occur. The engine must have been running for at least thirty seconds. "Start/Restart Time" is the amount of operation time before shutdown after the engine monitoring has just caused a shutdown. "NO" in the column indicates that the code will not cause engine shutdown.

Electronic Control System Operation

The electronic control system is integrally designed into the fuel system and into the air inlet system. The fuel delivery and injection timing are electronically controlled. In comparison to engines that are controlled mechanically, the electronic control system provides increased control of timing and increased control to the fuel to air ratio. Injection timing is achieved by precise control of injector firing time, and engine power is controlled by adjusting the firing duration. The ECM energizes the solenoid for the fuel injection pump in order to start the injection of fuel. The ECM will de-energize the solenoid for the fuel injection pump in order to stop the injection of fuel. Refer to the Systems Operation, Testing and Adjusting, "Fuel System" for a complete explanation of the fuel injection process.

The engine uses the following types of electronic components: input, control and output.

An input component is one that sends an electrical signal to the ECM. The signal that is sent varies in either voltage or in frequency when there is a change in some specific system of the vehicle. An example would be the engine speed/timing sensor or the coolant temperature sensor. The electronic control module sees the input sensor signal as information about the condition, environment, or operation of the vehicle.

An electronic control system component receives the input signals. Electronic circuits that are inside the ECM evaluate the signals. The ECM then supplies electrical energy to the output components of the system, which are in response to predetermined combinations of input signal values.

An output component is one that is operated by the ECM. An output component receives electrical energy from the ECM. The electrical energy is used to perform one of the following functions:

• Perform work. An example would be moving a solenoid plunger. An output component takes an active part in regulating or operating the vehicle.

• Give information or a warning. An example would be a light or an alarm to the operator of the vehicle or other person.

The output components control the engine in order to improve the performance of the engine. , minimize the fuel consumption of the engine, and reduce the emissions levels of the engine. A brief description of the sensors that are used in the electronic control system follows.

Atmospheric Pressure Sensor

The atmospheric pressure sensor is an absolute pressure sensor that measures crankcase pressure. Both the boost pressure and the oil pressure are communicated to the service tools and over the data link. The two pressures are calculated by subtracting the reading for the atmospheric pressure sensor. The atmospheric pressure sensor measures pressure from 0 (0) to 116 kPa (17 psi). The atmospheric pressure sensor is supplied with 5 VDC by the ECM.

Boost Pressure Sensor

The boost pressure sensor is an absolute pressure sensor that measures inlet manifold pressure. The difference between the inlet manifold pressure measurement and the pressure that is measured by the atmospheric pressure sensor is called the boost pressure. The information is communicated to the service tools and over the data link. The boost pressure sensor measures pressure from 20 kPa (3 psi) to 340 kPa (49 psi). The boost pressure sensor is supplied with 5 VDC by the ECM.

Coolant Level Sensor

The coolant level sensor is purchased by the OEM and the coolant level sensor is installed by the OEM. The coolant level sensor is the only optional sensor. The coolant level sensor is selected through the ECM Customer Programmable Parameter. The ECM Customer Programmable Parameter is protected by Customer Passwords.

Coolant Temperature Sensor

The engine coolant temperature is measured by an electronic sensor that is mounted on the water outlet housing. The signal from the coolant temperature sensor is used to modify the fuel mixture and the timing. This results in improved cold starting and improved cleanup of white smoke. The ECM supplies the coolant temperature sensor with 5.0 ± 0.5 VDC. The output voltage of the sensor is from 0.5 VDC to 4.5 VDC. The output voltage of the sensor depends on the temperature of the engine coolant. The coolant temperature sensor is used to indicate cold mode operation. The coolant temperature sensor is also used for engine monitoring.

Coolant Temperature Engine Monitoring Operation

If Engine Monitoring is programmed to "Derate" or programmed to "Shutdown" the Check Engine Lamp will flash. The Warning Lamp will then flash when the associated diagnostic code is active. When the Warning Lamp flashes, the engine is in Derate Mode.

Fuel Temperature Sensor

The Fuel Temperature is monitored in order to adjust the calculations for the fuel rate. The fuel temperature is also monitored for a power correction when the fuel temperatures exceed 30°C (86°F) in order to provide constant power. The maximum power correction is achieved at 70°C (158°F). A fuel temperature that exceeds 90°C (194°F) for ten minutes will cause a diagnostic code to be logged.

Inlet Air Temperature Sensor

Intake manifold temperature is used for the cooling fan driver and Engine Monitoring. The inlet air temperature sensor is used in order to warn the driver of an excessive inlet manifold air temperature. The air inlet temperature sensor will not cause an engine derate or an engine shutdown.

The air inlet temperature must exceed the temperatures that are indicated for thirty seconds before a diagnostic code is logged, following engine start-up. A diagnostic code for the High Inlet Manifold Temperature is triggered at 80°C (176°F). A diagnostic code for the Very High Inlet Manifold Temperature is triggered at 110°C (230°F). The codes that are associated with the inlet air temperature sensor are still available when Engine Monitoring is programmed to "OFF". This is unlike the diagnostic codes that are associated with the engine monitoring. The Warning Lamp is also turned on if Engine Monitoring is programmed to "Warning", "Derate", or "Shutdown".

Oil Pressure Sensor

The oil pressure sensor is an absolute pressure sensor that measures oil pressure in the gallery. The oil pressure is communicated over the data link and the oil pressure is displayed by the service tools. The ECM uses the sensor input only if the parameter for Engine Monitoring is programmed to "Warning", "Derate", or "Shutdown". 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.

Retarder Enable for the Compression Brake

The operation of the compression brake is provided through the RETARDER enable output if the engine is equipped with a compression brake. The RETARDER enable status is determined by the following inputs:

• engine rpm

• dash switch for the compression brake

• throttle position

• clutch switch

• cruise switch

Operation of the compression brake will be restricted under improper engine operating conditions. The following conditions allow the compression brake to be enabled.

• The engine speed must be greater than 1000 rpm.

• The throttle pedal can not be depressed.

• The clutch pedal can not be depressed.

• The cruise switch is off.

• The brake switch is energized.

Engine Speed/Timing Sensor

The engine speed/timing sensor is used to determine both engine speed and fuel injection timing. The sensor detects this information from a wheel on the camshaft. Timing calibration is performed by connecting a magnetic sensor. The sensor is connected through the vehicle speed circuit, sensing motion of the crankshaft.

Throttle Position Sensor

The throttle position sensor is an electronic sensor that is connected to the accelerator pedal. The throttle position sensor sends a Pulse Width Modulated Signal to the ECM.

Vehicle Speed Sensor

The vehicle speed sensor is an electromagnetic pickup that measures vehicle speed. The sensor measures vehicle speed from the rotation of the gear teeth that are in the drive train of the vehicle.

Check Engine Lamp

The check engine lamp is located on the dashboard of the vehicle. The check engine lamp can be used in order to communicate status. The check engine lamp can be used as a diagnostic lamp in order to communicate any problems with the operation of the electronic control system.

The check engine lamp will blink at five second intervals when a diagnostic fault is detected by the ECM. The check engine lamp should be ON and the check engine lamp should be flashing Diagnostic Code 55 whenever the START switch is turned ON but the engine is not running. This condition will test whether the light is operating correctly.

If the check engine lamp comes on and the check engine lamp stays on after the initial start-up, then the system has detected a fault. The check engine lamp or service tools can be used to identify the diagnostic code.

The dash mounted Cruise Control Switches are used to interrogate the ECM for system status. With the Cruise Control Switch in the OFF position, move the SET/RESUME switch to the RESUME position. The check engine lamp will begin to flash in order to indicate a two digit diagnostic code while the SET/RESUME switch is held in the RESUME position. The sequence of flashes represents the system diagnostic message. The first sequence of flashes adds up to the first digit of the diagnostic code. After a one second pause, a second sequence of flashes will occur. The second sequence of flashes represent the second digit of the diagnostic code. If necessary, additional diagnostic codes will follow after a three second pause. Additional diagnostic codes will be displayed in the same manner.

The check engine lamp is also used to monitor the Idle Shutdown Timer. The check engine lamp will start to flash at a rapid rate 90 seconds before the programmed idle time is reached. If the clutch pedal indicates a change in position or the service brake pedal indicates a change in position during the final 90 seconds, the idle shutdown timer will be disabled. The idle shutdown timer will then need to be reset.

Engine Control Module and Personality Module

The engine uses an Engine Control Module (ECM) that is based on a microprocessor. The ECM is isolated. The ECM is mounted on the rear left side of the cylinder block. The temperature of the ECM is maintained by fuel. The fuel circulates through a manifold between two circuit boards that are in the ECM. The fuel enters the ECM at the fuel inlet. The fuel exits the ECM at the fuel outlet.

All inputs and outputs to the ECM are designed to tolerate short circuits to battery voltage or ground without damage to the control. Resistance to radio frequency and electromagnetic interference are designed into the system. The system has passed tests for interference that is caused by two-way radios. The system has passed tests for switching noise.

The ECM power supply provides electrical power to all engine mounted sensors and actuators. Reverse voltage polarity protection and resistance to vehicle power system voltage swings or surges have been designed into the ECM. In addition to acting as a power supply, the ECM also monitors all sensor inputs. The ECM also provides the correct outputs in order to ensure desired engine operation.

The ECM contains memory in order to store customer specified parameters. The ECM also identifies a selected factory engine rating. The memory also contains a personality module identification code in order to prevent unauthorized tampering. The memory also contains a personality module identification code in order to prevent switching of engine ratings in the personality modules and other pertinent manufacturing information.

The wiring harness provides communication or signal paths to the various sensors. A boost sensor, an engine speed/timing sensor, the Data Link Connector, and the engine/vehicle connectors are examples. The personality module is installed inside the ECM. The personality module provides the programming that is necessary for the ECM to perform many functions. The Personality Module contains all of the engine performance and all of the certification information.

• engine timing

• air/fuel ratio

• rated fuel position control maps

Note: NOTE: The following parameters are customer specified parameters.

• Engine Power Rating

• Vehicle Identification Number

• "PTO Vehicle Speed Limit" (PTO VSL)

• "PTO Engine RPM Limit" (PTO RPM)

• "Low Gears Limit"

• "Intermediate Gears Limit"

• "Engine RPM At Vehicle Speed Limit" (Eng RPM At VSL)

• "Gear down Protection, Top Engine Limit" (TEL)

• "Vehicle Speed Limit" (VSL)

• "High Gear Turn On Speed" (HiGr On)

• "Low Cruise Control Set Limit" (LCC)

• "High Cruise Control Speed Set Limit" (HCC)

• "Retarder Coast/Latch"

• "Idle Shutdown Timer"

The customer specified parameters may be secured by customer passwords. An ECM may be programmed for all of the parameters or any combination of the parameters. For a brief explanation of each of the customer specified parameters, refer to the Operation and Maintenance Manual.

The ECM is programmed to run diagnostic tests on all inputs and outputs in order to separate a fault to a specific circuit. A diagnostic code can be displayed on the check engine lamp. The check engine lamp will flash representing a diagnostic fault code. A multimeter can be used to troubleshoot most problems. The ECM will also log most diagnostic codes that are generated during engine operation. The logged codes or the intermittent codes can be read by an electronic service tool.

Cooling Fan Driver

The ECM provides a signal in order to disable the cooling fan. The output of the ECM is high for "fan off". The "cooling fan disable" signal is for "ON/OFF" control of the fan. The "ON/OFF" control is based on the following items: coolant temperature, operation of the engine brake, engine speed, intake manifold air temperature and an optional control that is based on an OEM installed high pressure switch for an air conditioner. All other control of the cooling fan is the responsibility of the OEM.

The ECM turns off the cooling fan driver while the engine is cranking. This prevents unnecessary cycling of the cooling fan. Because an electrical open circuit is the most likely failure mode, Caterpillar recommends a normally open relay for this circuit.