INTRODUCTION
This article covers basic description and operation of engine performance-related systems and components. Read this article before diagnosing vehicles or systems with which you are not completely familiar.
INTERCOOLER
Note. Intercooler may also be referred to as a charge air cooler.
Intercooler is a heat exchanger used to reduce intake air temperature from turbocharger. Cooling of intake air results in an increased air density for producing greater power and efficiency. Intercooler is located in front of radiator. (Scheme 1)
Scheme 1
TURBOCHARGER
Note. Turbocharger is not serviceable and must be replaced as a complete assembly.
Turbocharger is mounted on exhaust manifold. (Scheme 2) Exhaust gases rotate turbine wheel along with the shaft and compressor wheel. Rotating of compressor wheel forces an increased amount of airflow (boost pressure) through intercooler and then into intake manifold where the air is distributed into each cylinder. Supplying increased airflow provides improved engine performance and fuel economy, lower exhaust smoke density, altitude compensation and reduced engine noise.
Turbocharger is lubricated by pressurized engine oil from engine oiling system. Excess engine oil is returned through turbocharger oil return line into the cylinder block.
Turbocharger contains a turbocharger wastegate which is used for controlling boost pressure at high speeds. Wastegate actuator and control rod are used for controlling turbocharger wastegate. Control rod length is factory preset and no adjustment is required unless the wastegate assembly was damaged. Control rod length MUST NOT be altered to obtain higher boost pressures for operating of turbocharger wastegate. If higher boost pressures are required to open turbocharger wastegate after adjusting control rod, turbocharger will be damaged.
Scheme 2
POWERTRAIN CONTROL MODULE (PCM)
PCM is a preprogrammed, dual microprocessor digital computer which does not directly regulate or control diesel fuel system operation, but does operate or control the following systems.
* A/C System Operation
* Automatic Shutdown (ASD) Relay
* Certain Transmission Shift Features (A/T Only)
* Certain Warning Lights
* Charging System
* Cruise Control System
* Intake Manifold Air Heater
* Tachometer
* Torque Convertor Clutch Engagement (A/T Only)
* Transmission Overdrive Solenoid (A/T Only)
PCM uses input signals from various switches and sensors to control output devices in order to achieve optimum engine performance for all operating conditions. See INPUT DEVICES and OUTPUT DEVICES under COMPUTERIZED ENGINE CONTROLS. PCM is located at passenger's side rear corner of engine compartment, on the firewall. (Scheme 3) PCM contains a self-diagnostic system which stores a Diagnostic Trouble Code (DTC) if a system failure exists. DTC may be retrieved from PCM for system diagnosis.
Scheme 3
Note. Components are grouped into 2 categories. The first category covers INPUT DEVICES, which control or produce voltage signals monitored by the PCM. The second category covers OUTPUT SIGNALS, which are components controlled by the PCM.
A/C SWITCH
When A/C switch is in ON position, an input signal is delivered from A/C switch to PCM to indicate that A/C operation has been requested. Once A/C operation has been requested, an A/C request signal is delivered to PCM from A/C high-pressure cut-out and A/C low-pressure cut-out switches. The A/C request signal indicates that evaporator pressure is within proper range for A/C operation. PCM uses A/C request signal to cycle A/C compressor clutch by using an A/C clutch relay. If A/C high-pressure cut-out switch or A/C low-pressure cut-out switch opens, A/C request signal will not be delivered to the PCM. PCM will then open ground circuit for A/C clutch relay and A/C compressor clutch will be disengaged.
The A/C clutch relay is located in power distribution center at driver's side front corner of engine compartment, near the battery. The A/C high-pressure cut-out switch is located on discharge line, near A/C compressor. The A/C low-pressure cut-out switch is located on top of accumulator.
AUTOMATIC SHUTDOWN (ASD) RELAY
A 12-volt input signal is delivered from ASD relay to PCM when ASD relay is energized. If PCM does not receive a 12-volt input signal when ASD relay is energized, a Diagnostic Trouble Code (DTC) will be stored in PCM. ASD relay is located in power distribution center at driver's side front corner of engine compartment, near the battery. Automatic Shutdown (ASD) relay may also be referred to as Auto Shutdown (ASD) relay.
BATTERY VOLTAGE
Battery voltage input signal provides operating voltage to PCM. This input signal keeps the PCM memory alive and informs the PCM what generator output voltage is when engine is running. PCM memory is used to store Diagnostic Trouble Codes (DTCs), throttle position sensor voltages from previous key cycles and provides a speed control adaptive memory.
BATTERY TEMPERATURE SENSOR
Battery temperature sensor delivers input signal to PCM to indicate the battery temperature. PCM uses battery temperature for controlling the charging system. Battery temperature sensor is snapped into battery tray below driver's side battery.
BRAKE SWITCH
Brake switch delivers input signal to PCM to indicate when brakes are applied. PCM uses input signal for controlling cruise control system and transmission torque converter clutch on A/T models. Brake switch is located near top of brake pedal and may also be referred to as brakelight switch.
CRUISE CONTROL SYSTEM SWITCHES
Six different cruise control functions, using 3 momentary contact switches, are monitored through this multiplexed input signal to PCM. Resistance monitored at this input signal, in conjunction with the length of time the PCM measures the resistance, determines which switch feature has been selected.
The 3 momentary contact switches for the cruise control system is ON/OFF switch, SET/COAST switch and RESUME/ACCEL switch. Cruise control system operates between 35-85 MPH and is controlled by signals from brake switch, clutch switch (M/T models), park/neutral switch (A/T models), vehicle speed sensor, engine speed sensor and throttle position sensor (A/T models and M/T models with EGR).
DATA LINK CONNECTOR
Data Link Connector (DLC) provides an input signal to PCM when using scan tool to retrieve Diagnostic Trouble Codes (DTCs) from PCM. Input signal may also be used when performing various tests on the PCM and electronic control system.
ENGINE COOLANT TEMP. SENSOR (CALIF. WITH EGR)
Engine coolant temperature sensor delivers input signal to PCM to indicate engine coolant temperature. PCM uses input signal for controlling EGR operation. Engine coolant temperature sensor is located on driver's side of engine, behind fuel filter/water separator, just below intake manifold. (Scheme 2)
ENGINE SPEED SENSOR
Engine speed sensor may also be referred to as Crankshaft Position (CKP) sensor. Engine speed sensor delivers input signal to PCM to indicate engine speed. PCM uses engine speed input signal along with Vehicle Speed Sensor (VSS) input signal and throttle position sensor input signal for controlling transmission overdrive shifts and transmission torque converter clutch on A/T models. PCM also uses engine speed input signal for controlling operation of Auto Shutdown (ASD) for controlling generator field, cruise control operation and tachometer operation. Engine speed sensor is located on front of timing gear cover, just above vibration damper.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
Intake manifold air temperature sensor is a variable thermistor sensor located on top of intake manifold, behind intake manifold air heater. (Scheme 4) Intake manifold air temperature sensor delivers an input signal to PCM to intake manifold air temperature.
Intake manifold air temperature sensor resistance increases at colder temperatures and decreases at warmer temperatures. PCM uses input signal for determining when, and for how long to operate intake manifold air heater. (Scheme 5) Intake manifold air temperature sensor may also be referred to as intake air temperature sensor.
Scheme 4
Scheme 5
PARK/NEUTRAL SWITCH (A/T MODELS)
Park/neutral switch delivers input signal to PCM to indicate if transmission is in Park, Neutral or Drive. PCM uses input signal for controlling cruise control system, transmission torque converter clutch solenoid and transmission overdrive solenoid. When park/neutral switch is in Park or Neutral, switch also provides a ground circuit for the engine starting system. Park/neutral switch is located on driver's side of transmission, near shift linkage.
Throttle Position Sensor (A/T Models & M/T Models With EGR) -Throttle Position (TP) sensor is mounted on side of fuel injection pump near front of engine. (Scheme 2) TP sensor provides input signal to PCM to indicate throttle position. PCM uses input signals from TP sensor, engine speed sensor and Vehicle Speed Sensor (VSS) for controlling transmission torque converter clutch and transmission overdrive shifts on A/T models. TP sensor is used for controlling EGR system on Calif. applications.
TRANSMISSION GOVERNOR PRESSURE SENSOR (A/T MODELS)
Transmission governor pressure sensor delivers input signal to PCM to indicate transmission governor pressure. PCM uses input signal for controlling governor pressure by use of governor pressure solenoid on transmission valve body.
TRANSMISSION OVERDRIVE SWITCH (A/T MODELS)
Transmission overdrive switch may be referred to as overdrive/override switch, OD switch or overdrive off switch. When vehicle operator depresses transmission overdrive switch on instrument panel, an input signal is delivered to the PCM. The PCM uses input signal for controlling transmission overdrive shifts by use of transmission overdrive solenoid on transmission valve body. When ignition is first turned on, transmission overdrive switch is in ON position, allowing transmission overdrive operation. If transmission overdrive switch is depressed once, switch is in OFF position, allowing no transmission overdrive upshift. If transmission overdrive switch is depressed again, switch returns to the ON position, allowing transmission overdrive operation.
TRANSMISSION SPEED SENSOR (A/T MODELS)
Transmission speed sensor may also be referred to as transmission output shaft speed sensor. Transmission speed sensor is located on overdrive case at rear of transmission. Transmission speed sensor delivers input signal to PCM to indicate transmission output shaft speed.
TRANSMISSION TEMPERATURE SENSOR (A/T MODELS)
Transmission temperature sensor is located on transmission valve body, incorporated into governor pressure sensor. Transmission temperature sensor monitors transmission fluid temperature and delivers input signal to PCM. PCM uses input signal for controlling torque converter clutch operation, transmission overdrive shifts and governor pressure.
PCM prevents torque converter clutch engagement and transmission overdrive operation when transmission fluid temperature is less than 50°F (10°C). If transmission fluid temperature is more than 260°F (126°C), PCM forces a 4-3 downshift and engages torque converter clutch until transmission fluid cools down. Once transmission fluid cools to less than 230°F (110°C), PCM allows a 3-4 shift again.
VEHICLE SPEED SENSOR
Vehicle Speed Sensor (VSS) is mounted on transmission extension housing (2WD) or on transfer case extension housing (4WD). The VSS delivers input signal to PCM to indicate vehicle speed and distance traveled. PCM uses input signal for controlling control cruise control system. PCM also uses input signal for controlling transmission overdrive shifts and transmission torque converter operation on A/T models.
WATER-IN-FUEL (WIF) SENSOR
WIF sensor is located in bottom of fuel filter/water separator. (Scheme 2) WIF sensor delivers input signal to PCM when water exists in fuel filter/water separator. As water level increases, resistance across WIF sensor decreases. PCM compares decrease in resistance to a high water standard value. When resistance is 30,000-40,000 ohms, PCM will turn on WATER-IN-FUEL warning light in instrument panel. PCM monitors input signal when ignition switch is turned to ON position and continues to monitor until intake manifold air heater post-heat cycle is complete.
A/C CLUTCH RELAY
The PCM controls A/C compressor operation by controlling ground circuit for A/C clutch relay. PCM de-energizes A/C clutch relay if engine coolant temperature is more than 257°F (125°C). The A/C clutch relay is located in power distribution center at driver's side front corner of engine compartment, near the battery.
AUTO SHUTDOWN (ASD) RELAY
The PCM controls ASD operation by controlling ground circuit for ASD relay. ASD provides voltage to operate generator field control for charging system. ASD relay is located in power distribution center at driver's side front corner of engine compartment, near the battery.
CRUISE CONTROL SYSTEM
PCM regulates cruise control system operation by controlling vacuum at cruise control servo. Vacuum is controlled by use of vacuum and vent solenoids in cruise control servo.
PCM provides output information at Data Link Connector (DLC) when using scan tool to perform various tests on the PCM and electronic control system.
EGR VALVE VACUUM REGULATOR SOLENOID (CALIF. MODELS ONLY)
EGR valve regulator solenoid controls vacuum supply from vacuum pump to the EGR valve for EGR valve operation. PCM uses input signals from engine coolant temperature sensor, intake manifold air temperature sensor and throttle position sensor for controlling operation of EGR valve vacuum regulator solenoid. EGR valve vacuum regulator solenoid is located on driver's side of engine, just in front of EGR valve, near inside of fuel injection pump.
GENERATOR FIELD
PCM provides output signals to generator field for regulating charging system voltage at 12.9-15.0 volts.
GENERATOR LIGHT
If PCM senses a low charging system condition, generator light on instrument panel will be turned on. Generator light may also come on momentarily at low idle speed when all accessories are on.
INTAKE MANIFOLD AIR HEATER RELAYS
Intake manifold air heater relays provide voltage to intake manifold air heater for warming of intake air. Intake manifold air heater relays are energized by PCM based on input signals from intake manifold air temperature sensor, engine speed sensor and Vehicle Speed Sensor (VSS).
Intake manifold air heater relays are not energized when intake manifold air temperature is greater than 59°F (15°C) or during engine cranking. Intake manifold air heater relays are mounted on inner wheelwell, below driver's side battery. (Scheme 6)
Scheme 6
MALFUNCTION INDICATOR LIGHT (MIL)
The MIL is located on the instrument panel and may also be referred to as the CHECK ENGINE light. MIL comes on for a short period and then goes off as a bulb and wiring circuit test each time ignition is turned on.
If PCM receives an incorrect signal or receives no signal from certain sensors or components, PCM will turn on the MIL to warn the driver that a malfunction exists in the electronic system. MIL may also be used to display Diagnostic Trouble Codes (DTCs). For additional information on MIL usage, see TESTS W/CODES - 5.9L article.
TACHOMETER
PCM delivers output signal to operate tachometer on instrument panel to indicate engine RPM.
TRANSMISSION RELAY (A/T MODELS)
Transmission relay may be referred to as transmission control relay. Transmission relay ground circuit is controlled by the PCM. When ground circuit is completed, transmission relay supplies voltage to solenoid assembly on the transmission. Transmission relay is located in power distribution center at driver's side front corner of engine compartment, near the battery.
TRANSMISSION OVERDRIVE SOLENOID (A/T MODELS)
PCM delivers output signal to transmission overdrive solenoid for controlling transmission overdrive shifts. Transmission overdrive solenoid is located on transmission valve body.
TRANSMISSION OVERDRIVE INDICATOR LIGHT (A/T MODELS)
PCM delivers output signal to operate transmission overdrive indicator light in accordance with position of the transmission overdrive switch. If overdrive is turned off with transmission overdrive switch, transmission overdrive indicator light will be turned on. Transmission overdrive indicator light is located on transmission overdrive switch on instrument panel.
TRANSMISSION TEMPERATURE WARNING LIGHT (A/T MODELS WITH HEAVY-DUTY TRANSMISSION)
PCM delivers output signal to turn on transmission temperature warning light on the instrument panel if transmission fluid temperature is determined to be greater than 280°F (138°C) by the transmission temperature sensor.
Transmission Torque Converter Clutch Solenoid (A/T Models) -PCM delivers an output signal to operate transmission torque converter clutch solenoid for torque converter lock-up. PCM uses various input signals such as transmission temperature, output shaft speed, engine speed, throttle position and brake switch position to determine operation of transmission torque converter clutch solenoid. Transmission torque converter clutch solenoid is located on transmission valve body.
WAIT-TO-START WARNING LIGHT
WAIT-TO-START warning light on instrument panel will come on for a short period and then go off as a bulb and wiring circuit test each time ignition is turned on. If PCM determines intake manifold air temperature is less than 59°F (15°C) by input signal received from intake manifold air temperature sensor, PCM delivers output signal to operate WAIT-TO-START warning light on instrument panel and operate intake manifold air heater for a preheat cycle.
Warning light will remain on until preheat cycle is completed. Warning light will flash on and off if intake manifold air temperature sensor signal to PCM is not within a specified value and Diagnostic Trouble Code (DTC) will be stored in PCM memory.
WATER-IN-FUEL WARNING LIGHT
Warning light on instrument panel will come on for a short period and then go off as a bulb and wiring circuit test each time ignition is turned on. If PCM determines water exists in fuel/water separator by input signal from Water-In-Fuel (WIF) sensor, PCM will deliver output signal to turn on the warning light.
FUEL INJECTION PUMP
A camshaft-driven Bosch P7100 in-line fuel injection pump is used to supply high pressure fuel to each fuel injector in precise metered amounts at the correct time. (Scheme 2)and (Scheme 7). An RQV-K governor, mounted at rear of fuel injector pump, has a pump timing feature to allow the pump shaft to be properly positioned at TDC on compression stroke for cylinder No. 1. Fuel injection occurs near completion of compression stroke for each cylinder.
As engine speed increases, internal pump pressure increases. An Airflow Control (AFC) is mounted on top of governor. AFC regulates fuel delivery to match intake manifold pressure (turbocharger boost pressure) for more accurate emission control. Fuel injection pump contains an overflow valve which allows excess fuel to return to the fuel tank. Overflow valve is located on side of fuel injection pump and is used to attach the fuel return line to the fuel injection pump.
Scheme 7
FUEL SHUTDOWN SOLENOID
Fuel shutdown solenoid is located on side of fuel injection pump. (Scheme 2)and (Scheme 8). Fuel shutdown solenoid electrically controls starting and stopping of engine regardless of accelerator pedal position. With ignition off, spring-loaded fuel shutdown solenoid plunger is in shutdown position. When ignition switch is in ON or START positions, battery voltage is supplied to fuel shutdown solenoid through fuel shutdown solenoid relay.
When battery voltage is supplied to fuel shutdown solenoid, plunger in fuel shutdown solenoid pulls lever upward to the run position, allowing fuel to flow for engine operation. (Scheme 8) Fuel shutdown solenoid and fuel shutdown relay are not controlled by Powertrain Control Module (PCM). Fuel shutdown relay is located near master cylinder. (Scheme 9)
FUEL TRANSFER PUMP
Fuel transfer pump is located on driver's side of cylinder block, above starter. (Scheme 2) Fuel transfer pump is camshaft-driven pump which supplies low fuel pressure from fuel tank, through fuel heater/pre-filter, fuel filter/water separator and to fuel injection pump. Fuel transfer pump contains internal check valves to prevent fuel from bleeding back into fuel tank during engine shutdown. Fuel transfer pump contains a rubber primer button for priming and bleeding air from fuel system. A defective fuel transfer pump may cause loss of engine power, excessive White smoke and/or hard starting.
IN-TANK FUEL FILTER
A separate in-tank fuel filter is attached to bottom of fuel tank module. In-tank fuel filter does not require service under normal conditions.
Scheme 8
AIRFLOW CONTROL (AFC)
AFC is located on top of governor on fuel injection pump. (Scheme 2)and (Scheme 7). AFC regulates fuel delivery to match intake manifold pressure (turbocharger boost pressure) for more accurate emission control.
FUEL INJECTOR
Fuel injector delivers atomized fuel into the cylinder. During fuel injection, fuel pressure from fuel injection pump increases to fuel injector opening pressure or pop pressure of 3822 psi (26,252 kPa). This is the pressure required to lift fuel injector needle valve from its seat, allowing fuel to be injected into the cylinder. Once fuel pressure decreases to less then the opening pressure, a spring forces needle valve closed and stops fuel injection into the cylinders.
FUEL INJECTION TIMING
Fuel injection pump timing is controlled by RQV-K governor which has a pump timing feature to allows the pump shaft to be properly positioned at TDC on compression stroke for cylinder No. 1. Indexing governor fly weight assembly to shaft during assembly of establishes fuel injection pump timing. Timing advances as engine speed increases.
RQV-K GOVERNOR
An RQV-K governor is mounted at rear of fuel injection pump. (Scheme 2)and (Scheme 7). Balance between RQV-K governor and throttle lever position controls the amount of fuel to be injected. If seals are broken on external adjustment screw, fuel rate may be out of adjustment. Warranty of pump governor and engine may be void if seals are tampered with or removed.
THROTTLE LEVER
Amount of fuel injected and engine speed are controlled by throttle lever on side of fuel injection pump. (Scheme 2) Restricted travel of throttle lever may cause a power loss.
FUEL FILTER/WATER SEPARATOR
Fuel filter/water separator is located on driver's side of engine and contains a Water-In-Fuel (WIF) sensor and a drain valve. (Scheme 2) The WIF sensor delivers an input signal to Powertrain Control Module (PCM) when water exists in fuel filter/water separator. PCM will then turn on instrument panel WATER-IN-FUEL warning light. WATER-IN-FUEL warning light informs operator to drain water from fuel filter/water separator to prevent damage to fuel system components. Water may be drained from fuel filter/water separator by using drain valve on fuel filter/water separator.
FUEL HEATER
Fuel heater is used to prevent diesel fuel from waxing during cold temperatures. Fuel heater is located on driver's side of engine, just above the pre-filter. (Scheme 2) Fuel flows from fuel tank to fuel heater and then to fuel transfer pump. (Scheme 10) Voltage to operate fuel heater is provided from ignition switch, through fuel heater relay and to fuel heater. Fuel heater relay is located next to master cylinder. (Scheme 9) Fuel heater and fuel heater relay are not controlled by Powertrain Control Module (PCM).
Fuel heater contains a fuel heater temperature sensor that senses the fuel temperature. When temperature is less than 40°F (4.4°C), fuel heater temperature sensor allows current to flow to the fuel heater to warm the fuel. When temperature is more than 80°F (26.7°C), fuel heater temperature sensor turns off the current flow to the fuel heater.
Scheme 9
Scheme 10
CALIF. MODELS ONLY
EGR system is used to reduce exhaust emissions. EGR system consists of EGR valve, EGR tube, EGR valve vacuum regulator solenoid and one-way check valve.
EGR valve and EGR tube allow exhaust gases to be recirculated into the air intake. (Scheme 2) EGR valve operation is controlled by EGR valve vacuum regulator solenoid. EGR valve regulator solenoid controls vacuum supply from vacuum pump to the EGR valve for EGR valve operation. The Powertrain Control Module (PCM) uses input signals from engine coolant temperature sensor, intake manifold air temperature sensor and throttle position sensor for controlling operation of EGR valve vacuum regulator solenoid. EGR valve vacuum regulator solenoid is located on driver's side of engine, just in front of EGR valve, near inside of fuel injection pump. One-way check valve is used to quickly release vacuum to EGR valve if EGR system operation is shut off. One-way check valve is located in vacuum line, near EGR valve.
EGR system operates if vacuum pump is operating, PCM determines engine coolant temperature is more than 140°F (60°C) but less than 220°F (104°C), and intake air temperature is more than 20°F (6.6°C), but less than 170°F (76.7°C). EGR system will shut off if PCM determines a rapid acceleration is occurring, throttle is at wide open position, or throttle remains at the same position for 2 continuous minutes to indicate idle or normal cruising speed. If certain problems exist in the EGR system, a Diagnostic Trouble Code (DTC) will be stored in the PCM for system diagnosis.
INTAKE MANIFOLD AIR HEATER SYSTEM
Intake manifold air heater is used to warm intake air during cold starting conditions to eliminate the need for glow plugs. Intake manifold air consists of 2 grid heaters installed between air inlet housing and intake manifold. (Scheme 5)
PCM energizes intake manifold air heater relays to provide voltage to intake manifold air heater before and after starting depending on input signals from intake manifold air temperature sensor, engine speed sensor and Vehicle Speed Sensor (VSS). Intake manifold air heater relays are not energized when intake manifold air temperature is greater than 59°F (15°C) or during engine cranking. Intake manifold air heater relays are mounted on inner wheelwell, below driver's side battery. (Scheme 6)
Intake manifold air temperature sensor monitors intake manifold air temperature and delivers an input signal to Powertrain Control Module (PCM) for controlling intake manifold air heater. Intake manifold air temperature sensor is located in intake manifold cover. (Scheme 2)and (Scheme 4).
SELF-DIAGNOSTIC SYSTEM
Powertrain Control Module (PCM) is located at passenger's side rear corner of engine compartment, on the firewall. (Scheme 3) PCM contains a self-diagnostic system which stores a Diagnostic Trouble Code (DTC) if a system failure exists. DTC may be retrieved from PCM for system diagnosis. For additional information on self-diagnostic system, see appropriate TESTS W/CODES - 5.9L article.
Powertrain Control Module (PCM) operates transmission overdrive solenoid for controlling transmission overdrive shifts. Transmission overdrive solenoid is located on transmission valve body.
TRANSMISSION TORQUE CONVERTER CLUTCH SOLENOID
Powertrain Control Module (PCM) operates transmission torque converter clutch solenoid for torque converter lock-up. PCM uses various input signals such as transmission temperature, output shaft speed, engine speed, throttle position and brake switch position to determine when to operate transmission torque converter clutch solenoid. Torque converter clutch solenoid is located on transmission valve body.
See also:
• TESTS W/CODES - 5.9L