Engine Controls - 6.6L (LB7) (Introduction): Overview Chevrolet Silverado 3500

Very Cold Weather Operation

If the vehicle is driven in very cold temperatures and can not get a winterized Number 2-D that has been adapted to cold weather or a Number 1-D, use one gallon of kerosene for every two gallons of diesel fuel. Once you add kerosene, run the engine for several minutes to mix the fuels. Only add kerosene when the temperature falls below -18° C (0° F), because the fuel economy and lubricating qualities of kerosene is not as good as that of diesel fuel.

In cold weather, the fuel filter may become clogged (waxed). To unclog the filter, move the vehicle to a warm garage area and warm the filter to a temperature between 0-10° C (32-50° F). Replacing the filter is not necessary.

If the vehicle is driven in very cold temperatures and can not get a winterized Number 2-D that has been adapted to cold weather or a Number 1-D, use one gallon of kerosene for every two gallons of diesel fuel. Once you add kerosene, run the engine for several minutes to mix the fuels. Only add kerosene when the temperature falls below -18° C (0° F), because the fuel economy and lubricating qualities of kerosene is not as good as that of diesel fuel.

In cold weather, the fuel filter may become clogged (waxed). To unclog the filter, move the vehicle to a warm garage area and warm the filter to a temperature between 0-10° C (32-50° F). Replacing the filter is not necessary.

Engine Controls Schematic Icons

Engine Controls Schematic Icons Icon Icon Definition NOTE: The OBD II symbol is used on the circuit diagrams in order to alert the technician that the circuit is essential for proper OBD II emission control circuit operation. Any circuit which fails and causes the malfunction indicator lamp (MIL) to turn ON, or causes emissions-related component damage, is identified as an OBD II circuit

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Engine Control Module (ECM) Description

The engine control module (ECM) processes the various input information. The ECM sends the necessary electrical responses to control fuel delivery.

The input information has an interrelation to more than one output. One failed input can affect more than one systems operation.

Malfunction Indicator Lamp (MIL) Operation

The malfunction indicator lamp (MIL) is located in the instrument panel cluster. The MIL will display as either SERVICE ENGINE SOON or one of the following symbols when commanded ON

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The MIL indicates that an emissions related fault has occurred and vehicle service is required.

The following is a list of the modes of operation for the MIL

1. The MIL illuminates when the ignition is turned ON, with the engine OFF. This is a bulb test to ensure the MIL is able to illuminate.
2. The MIL turns OFF after the engine is started if a diagnostic fault is not present.
3. The MIL remains illuminated after the engine is started if the control module detects a fault. A diagnostic trouble code (DTC) is stored any time the control module illuminates the MIL due to an emissions related fault. The MIL turns OFF after three consecutive ignition cycles in which a Test Passed has been reported for the diagnostic test that originally caused the MIL to illuminate.
4. The MIL flashes if the control module detects a misfire condition which could damage the catalytic converter.
5. When the MIL is illuminated and the engine stalls, the MIL will remain illuminated as long as the ignition is ON.
6. When the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition is cycled OFF and then ON.

Fuel System Overview

The fuel tank (5) stores the fuel supply. A mechanical fuel injection pump (10), located below the engine intake, draws fuel through the fuel injector control module (6) and the fuel filter (7). The fuel is used as a coolant for the fuel injector control module. The fuel pump output is controlled by the ECM, and provides fuel at the pressure needed by the fuel injectors (3). The fuel injectors supply fuel directly to the combustion chambers of the engine. A separate pipe returns unused fuel through a fuel cooler (4) and to the fuel tank.

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The fuel tanks store the fuel supply. The primary fuel tank (2) is located on the left side of the vehicle. On vehicles that are equipped with dual fuel tanks, the auxiliary fuel tank is located in the rear of the vehicle. The fuel tanks are each held in place by 2 metal straps that attach to the frame. The fuel tanks are molded from high density polyethylene.

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The fuel filler cap has a torque-limiting device that prevents the cap from being over tightened. To install, turn the cap clockwise until you hear audible clicks. This indicates that the cap is fully seated.

Glow Plug System Description

In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.

Control of the glow plugs is accomplished by moving the logic for controlling the heat of the plugs to the engine control module (ECM). The new logic can incorporate the higher accuracy of digital processing compared to the previous analog controller. Additionally, logic involving engine speed and estimates of engine combustion can be added to the traditional time and temperature data used in the previous controller. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability.

A normal functioning system operates as follows

1. Turn the ignition ON with the engine OFF, and at room temperature.
2. The glow plugs turn ON for between 1 and 16 seconds.
3. If the engine is cranked during or after the above sequence, the glow plugs may cycle ON and OFF after the engine control switch is returned from the crank position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.

The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.

The ECM provides glow plug operation after starting a cold engine. This post-start operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.

Exhaust Gas Recirculation (EGR) System Description

The exhaust gas recirculation (EGR) system is used to reduce the amount of nitrogen oxide (NOx) emission levels caused by combustion temperatures exceeding 816° C (1,500° F). It does this by introducing small amounts of exhaust gas back into the combustion chamber. The exhaust gas absorbs a portion of the thermal energy produced by the combustion process and thus decreases combustion temperature. The EGR system will only operate under specific temperature, barometric pressure and engine load conditions in order to prevent driveability concerns and to increase engine performance.

The EGR system consists of the following components

1. EGR Valve The EGR valve is vacuum operated. The EGR valve is used to transmit exhaust gases from the exhaust system to the intake manifold to be recirculated into the combustion process.
2. Vacuum Pump Vacuum for the EGR vacuum control system is created by a belt driven mechanical pump called a vacuum pump. When the engine is running, the vacuum pump is operating at all times.
3. EGR Valve Vacuum Control Solenoid The EGR valve vacuum control solenoid is located in the EGR vacuum control system between the vacuum pump and the EGR vacuum vent solenoid. The ECM pulse width modulates (PWM) the ground path of the EGR valve vacuum control solenoid allowing metered vacuum from the vacuum pump to open the EGR valve to the desired position. The EGR valve vacuum control solenoid is supplied ignition voltage through the ignition 1 voltage circuit from the Fuel HT fuse. The EGR valve vacuum control solenoid is normally closed.
4. EGR Vacuum Vent Solenoid The EGR vacuum vent solenoid is located between the EGR valve vacuum control solenoid and the EGR vacuum sensor. The ECM opens the EGR vacuum vent solenoid, allowing vacuum from the vacuum pump to build in the EGR vacuum control system. When the EGR vacuum vent solenoid is commanded closed, the EGR vacuum control system is vented to atmosphere which will cause the EGR valve to close very fast. The ECM controls the EGR vacuum vent solenoid by switching the ground path ON and OFF. Ignition voltage is supplied through the ignition 1 voltage circuit from the Fuel HT fuse. The EGR vacuum vent solenoid is normally closed.
5. EGR Throttle Valve Vacuum Control Solenoid The EGR throttle valve vacuum control solenoid is located in the EGR vacuum control system between the vacuum pump and the EGR throttle valve. The ECM opens the EGR throttle valve vacuum control solenoid, allowing vacuum from the vacuum pump to close the EGR throttle valve. Diesel engines do not create enough engine vacuum on their own to allow the EGR gases into the combustion process. The EGR throttle valve, when closed, creates a restriction of incoming fresh air to the engine in order to create engine vacuum. When the ECM commands the EGR valve to open, the EGR throttle valve will be commanded closed. The ECM controls the EGR throttle valve vacuum control solenoid by switching the ground path ON and OFF. Ignition voltage is supplied through the ignition 1 voltage circuit from the Fuel HT fuse. The EGR throttle valve vacuum control solenoid is normally closed.
6. EGR Vacuum Sensor The EGR vacuum sensor is located in the EGR vacuum control system between the EGR vacuum vent solenoid and the EGR valve. The ECM uses the EGR vacuum sensor to monitor the amount of vacuum that is available to the EGR valve. The ECM will make adjustments to the EGR vacuum control system in order to obtain the vacuum level necessary to achieve the proper EGR valve position. The EGR vacuum sensor is interfaced with the ECM by a 5-volt reference circuit, a low reference circuit and a signal circuit.
7. MAF Sensor The MAF sensor is located in the air intake system between the air filter and the EGR valve out-take port. The ECM monitors the Mass Air Flow (MAF) sensor signal to calculate the actual amount of EGR flow into the intake manifold. When the EGR valve is opened, the MAF rate will decrease. When the EGR valve vacuum control solenoid is operated at 50-70 percent duty cycle, the MAF rate should drop at least 4 g/s.
8. EGR Valve Cooler The EGR valve cooler is mounted on the right intake manifold, between the EGR valve and the exhaust pipe. Engine coolant flows through the EGR valve cooler in order to lower the exhaust gas temperatures before it enters the EGR valve and intake manifold.
9. ECM The PCM calculates the amount of EGR needed based on the following inputs: The accelerator pedal position (APP) sensor The barometric pressure (BARO) sensor The boost sensor The engine coolant temperature (ECT) sensor The exhaust gas recirculation (EGR) vacuum sensor The intake air temperature (IAT) sensor The mass airflow (MAF) sensor The vehicle speed sensor (VSS) The engine speed

Air Intake System Description

The air intake system is used to direct cool air from the exterior of the engine compartment to the intake manifold. An air cleaner is incorporated into the system to keep dirt from entering the engine. The system also has a turbocharger to increase power, improve driveability and reduce emissions.

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The air cleaner restriction indicator is located on the air cleaner housing.

If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter.