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 overhaul procedures should only be performed by an authorized facility.
Turbocharger is mounted on exhaust manifold. (Scheme 1) 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, lower exhaust smoke density, altitude compensation and reduced engine noise. Turbocharger contains a wastegate which is used for controlling boost pressure at high speeds. 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.
COMPUTERIZED ENGINE CONTROLS
Two different module systems are used for powertrain control of diesel engine. The Engine Control Module (ECM), located on left side of engine, is used to control the fuel system. (Scheme 2) The Fuel Pump Control Module (FPCM) located on pump, is a separate component of ECM.
The Powertrain Control Module (PCM), located at right rear of engine compartment, is used for charging system, transmission and speed control functions. (Scheme 3) CCD Bus circuits connect the various vehicle control modules. These circuits are connected between ECM and PCM to allow communication between modules. Inputs and outputs are at each module.
Scheme 2
Scheme 3
ENGINE CONTROL MODULE (ECM)
Engine Control Module (ECM) uses input signals from various switches and sensors to control output devices in order to achieve optimum engine performance for all operating conditions. Components are grouped into 2 categories. The first category covers INPUT DEVICES, which control or produce voltage signals monitored by the ECM. The second category covers OUTPUT SIGNALS, which are components controlled by the ECM. See ECM INPUT DEVICES and ECM OUTPUT SIGNALS .
POWERTRAIN CONTROL MODULE (PCM)
Powertrain Control Module (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)
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. See PCM INPUT SIGNALS and ECM/PCM OUTPUT SIGNALS .
Accelerator Pedal Position Sensor (APPS)
APPS sensor is mounted on top left of engine. (Scheme 2) Sensor provides DC voltage input signal to Engine Control Module (ECM) to indicate throttle position. On previous engines, there were linkages between accelerator pedal, throttle position sensor and injection pump. On this engine, no linkage exists between accelerator pedal and injection pump. ECM uses input signals from APPS sensor to determine proper fuel delivery. ECM also outputs this signal to PCM.
Battery Voltage
Battery voltage input signal provides operating voltage to Engine Control Module (ECM). This input signal keeps ECM memory alive and informs ECM what generator output voltage is when engine is running. ECM memory is used to store Diagnostic Trouble Codes (DTCs), store APPS sensor voltages from previous key cycles and provide a speed control adaptive memory.
Camshaft Position Sensor (CMP)
Camshaft Position (CMP) sensor is a hall effect sensor (0-5 volts switched), located below injection pump in rear face of timing gear cover. Sensor is not used for fuel control. Sensor is used only for diagnostic purposes.
CCD Bus Circuits
These circuits are connected between Engine Control Module (ECM) and Powertrain Control Module (PCM) to allow communication between modules.
Crankshaft Position Sensor (CKP)
Crankshaft Position (CKP) sensor delivers input signal (35 tooth wheel with gap) to Engine Control Module (ECM) to indicate engine speed and crankshaft position. ECM uses CKP signal along with other input signals for controlling injector firing sequence and timing. Sensor is located below fuel transfer pump, on side of engine block. (Scheme 2)
Data Link Connector (DLC)
Data Link Connector (DLC) provides an input signal to Engine Control Module (ECM) when using scan tool to retrieve Diagnostic Trouble Codes (DTCs) from ECM. Input signal may also be used when performing various tests on the ECM and electronic control system. Data link connector is a 16-pin connector located at lower edge of driver's side of instrument panel, just above accelerator pedal.
Engine Coolant Temperature (ECT) Sensor
Engine coolant temperature sensor delivers input signal to Engine Control Module (ECM) to indicate engine coolant temperature. ECM uses input signal for controlling fuel control and timing. Engine coolant temperature sensor is located on front of head, near thermostat housing. (Scheme 2)
Fuel Injection Pump Control Module (FPCM)
Fuel Pump Control Module (FPCM) controls fuel pump using inputs from Engine Control Module (ECM). FPCM is integral to top of fuel pump. ECM and FPCM are interconnected together for fuel injection control.
Fuel Temperature Sensors
There are 2 fuel temperature sensors. One sensor is located inside injection pump, and will set DTC under high temperature conditions. Engine Control Module (ECM) will lower engine power if DTC is set. Other sensor is an integral part of fuel heater. See FUEL HEATER .
Intake Manifold Air Temperature (IAT) 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 Engine Control Module (ECM) to indicate intake manifold air temperature. ECM uses input signal for controlling intake manifold air heater, fuel control and timing.
Scheme 4
Manifold Air Pressure (MAP) Sensor (Boost Pressure)
Manifold Air Pressure (MAP) sensor, located at rear of intake manifold, sends input signal to Engine Control Module (ECM). ECM uses input signal for controlling fuel control, timing and engine protection. ECM will lower engine power if boost is too high.
Oil Pressure Sensor
Oil pressure sensor signal is input to Engine Control Module (ECM). ECM converts signal to pressure value. Value is sent on CCD Bus to instrument panel gauge/light. Oil pressure sensor is located on side of engine block, below ECM. (Scheme 2)
Power Take Off (PTO)
This input is used on vehicles equipped with a Power Take Off (PTO) unit. When PTO is engaged, Engine Control Module (ECM) will disable some OBD-II functions.
Water-In-Fuel (WIF) Sensor
WIF sensor is located in bottom of fuel filter/water separator. (Scheme 2) WIF sensor delivers input signal to Engine Control Module (ECM) when water exists in the fuel filter/water separator. As water level increases, resistance across WIF sensor decreases. ECM compares decrease in resistance to a high water standard value. When resistance is 30,000-40,000 ohms, ECM will turn on WATER-IN-FUEL warning light. WATER-IN-FUEL warning light is located on instrument panel, just below tachometer. ECM monitors input signal when ignition switch is in the ON position and continues to monitor input signal until intake manifold air heater post-heat cycle is complete.
A/C Switch
When A/C switch is in ON position, an input signal is delivered from A/C switch to Engine Control Module (ECM) to indicate that A/C operation has been requested. Once A/C operation has been requested, an A/C request signal is delivered to ECM from A/C high-pressure switch and A/C low-pressure switch. The A/C request signal indicates evaporator pressure is within proper range for A/C operation. ECM uses A/C request signal to cycle A/C compressor clutch by using an A/C clutch relay. A/C clutch relay may also be referred to as A/C compressor clutch relay. If A/C high-pressure switch or A/C low-pressure switch opens, A/C request signal will not be delivered to the ECM. ECM 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 switch is located on discharge line, near A/C compressor. The A/C low-pressure switch is located on top of accumulator.
Accelerator Pedal Position Sensor (APPS) Output From ECM
Accelerator Pedal Position Sensor (APPS) is mounted on top left of engine. (Scheme 2) Sensor provides DC voltage input signal to Engine Control Module (ECM) to indicate throttle position. On previous engines, there were linkages between accelerator pedal, throttle position sensor and injection pump. On this engine, no linkage exists between accelerator pedal and injection pump. APPS signal is sent on CCD Bus circuit from ECM to PCM.
Automatic Shutdown (ASD) Relay
A 12-volt input signal is delivered from ASD relay to Engine Control Module (ECM) when ASD relay is energized. If ECM does not receive a 12-volt input signal when ASD relay is energized, a Diagnostic Trouble Code (DTC) will be stored in ECM. 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 Temperature Sensor
Battery temperature sensor delivers input signal to Powertrain Control Module (PCM) to indicate the battery temperature. PCM uses battery temperature input to modify rate of output from the charging system. Battery temperature sensor is snapped into battery tray below driver's side battery.
Battery voltage input signal provides operating voltage to Powertrain Control Module (PCM). This input signal keeps PCM memory alive and informs PCM what generator output voltage is when engine is running. PCM memory is used to store Diagnostic Trouble Codes (DTCs), store APPS sensor voltages from previous key cycles and provide a speed control adaptive memory.
Brake Switch
Brake switch delivers input signal to Powertrain Control Module (PCM) to indicate when brakes are applied. PCM uses input signal for controlling cruise control system and transmission torque converter clutch operation on A/T models. Brake switch is located near top of brake pedal and may also be referred to as brakelight switch.
CKP Sensor
Crankshaft Position (CKP) sensor delivers input signal (35 tooth wheel with gap) to Engine Control Module (ECM) to indicate engine speed and crankshaft position. ECM uses CKP signal along with other input signals for controlling injector firing sequence and timing. Sensor is located below fuel transfer pump, on side of engine block. (Scheme 2)
Cruise Control System Switches
Cruise control system functions, controlled by momentary contact switches, are monitored through multiplexed input signal to Powertrain Control Module (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.
Data Link Connector (DLC) provides an input signal to Powertrain Control Module (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. DLC is a 16-pin connector located at lower edge of driver's side of instrument panel, just above accelerator pedal.
Fuel Level Sensor
The Powertrain Control Module (PCM) sends a 5-volt signal to the fuel level sensor. The fuel level sensor will return a signal to PCM. This signal is used for fuel gauge operation and to prevent setting a false misfire or fuel system trouble codes. If fuel level is less than 15 percent, PCM will not set code.
Ignition Sense
Ignition switch position input to Powertrain Control Module (PCM). PCM uses input to determine proper output functions, including cruise control, generator output, sensor supply and transmission functions.
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 Powertrain Control Module (PCM) to indicate transmission output shaft speed.
Overdrive Switch (A/T Models)
Transmission overdrive switch may be referred to as overdrive/override switch, OD switch or overdrive off switch. Transmission overdrive switch is located on end of gearshift lever. When vehicle operator depresses transmission overdrive switch, an input signal is delivered to the Powertrain Control Module (PCM). The PCM uses input signal for controlling transmission overdrive shifts by use of transmission overdrive solenoid on transmission valve body. Transmission overdrive switch is normally in the 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.
Park/Neutral Switch (A/T Models)
Park/neutral switch delivers input signal to Powertrain Control Module (PCM) to indicate if transmission is in Park, Neutral or Drive. PCM uses input signal for controlling cruise control system, transmission torque converter clutch operation 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 the driver's side of transmission, near shift linkage.
Transmission Governor Pressure Sensor (A/T Models)
Transmission governor pressure sensor delivers input signal to Powertrain Control Module (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 Temperature Sensor (A/T Models)
Transmission temperature sensor monitors transmission fluid temperature and delivers input signal to Powertrain Control Module (PCM). PCM uses input signal for controlling transmission torque converter clutch operation, transmission overdrive shifts and governor pressure. Transmission temperature sensor is located on transmission valve body, incorporated into governor pressure sensor.
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 & Distance
Vehicle speed sensor is no longer used. The vehicle speed and distance traveled are determined by rear wheel speed sensor. Rear wheel speed sensor is mounted on top of rear axle housing, above the ring gear. Rear wheel speed sensor delivers an input signal to Controller Anti-Lock Brake (CAB) to indicate vehicle speed and distance traveled. The CAB then delivers input signal to Powertrain Control Module (PCM) to indicate vehicle speed and distance traveled. PCM uses input signal for controlling control cruise control system and fuel system. The CAB is mounted on top of the hydraulic control unit. Hydraulic control unit contains the pump assembly that brakelines are attached to and is mounted in the engine compartment.
APPS & CKP Output To PCM
See ACCELERATOR PEDAL POSITION SENSOR (APPS) OUTPUT FROM ECM under PCM INPUT SIGNALS.
CCD Bus
These circuits are connected between Engine Control Module (ECM) and Powertrain Control Module (PCM) to allow communication between modules.
DLC Output
Data Link Connector (DLC) is connected to Engine Control Module (ECM). Using a scan tool, data can be retrieved (output) from ECM.
5-Volt Sensor Supply Output
Engine Control Module (ECM) supplies a 5-volt reference signal to the following sensors
- Crankshaft Position (CKP) Sensor
- Camshaft Position (CMP) Sensor
- Intake Air Temperature (IAT) Sensor
- Engine Oil Pressure Sensor
- Manifold Absolute Pressure (MAP) Sensor
Engine Control Module (ECM) also supplies voltage to the following sensors
- Accelerator Pedal Position Sensor (APPS)
- Intake Air Temperature (IAT) Sensor
- Engine Oil Pressure Sensor
- Engine Coolant Temperature (ECT) Sensor
- Manifold Absolute Pressure (MAP) Sensor
- Water-In-Fuel (WIF) Sensor
Fuel Injection Pump Relay
The Engine Control Module (ECM) energizes the fuel injection pump and integral Fuel Pump Control Module (FPCM) through the relay. When ignition is turned on, ECM supplies 12 volts to fuel injection pump relay, located in Power Distribution Center.
Fuel Pump Control Module (FPCM)
Fuel Pump Control Module (FPCM) controls fuel pump using inputs from Engine Control Module (ECM). FPCM is integral to top of fuel pump. ECM and FPCM are interconnected together for fuel injection control.
Fuel Transfer Pump
Engine Control Module (ECM) supplies power to fuel transfer pump. Transfer fuel pump supplies fuel under low pressure (14 psi) while engine is running to fuel injection pump. Fuel transfer pump supplies an excess of fuel to cool fuel injection pump. Excess fuel is returned to fuel tank by fuel injection pump.
Intake Manifold Air Heater Relays
Intake manifold air heater relays provide voltage to intake manifold air heater for warming of intake. (Scheme 5) Warming of intake air aids in engine starting and improved driveability during cold ambient temperatures. Intake manifold air heater relays are mounted on inner wheelwell, below driver's side battery. (Scheme 6) Intake manifold air heater relays are energized by Engine Control Module (ECM) based on input signals from intake manifold air temperature sensor, engine speed sensor and vehicle speed.
Scheme 5
Scheme 6
Malfunction Indicator Light (MIL)
The MIL is located on the instrument panel, just below tachometer 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 switch is turned to the ON position. If Engine Control Module (ECM) receives an incorrect signal or receives no signal from certain sensors or components, ECM will turn on the MIL to warn the driver that a malfunction exists in the electronic system.
Oil Pressure Gauge/Warning Light
Oil pressure gauge/warning light output from Engine Control Module (ECM) to instrument cluster is routed on CCD Bus circuit.
WAIT-TO-START Warning Light
WAIT-TO-START warning light is located on instrument panel, just below the speedometer. WAIT-TO-START warning light will come on for a short period and then go off as a bulb and wiring circuit test each time ignition switch is turned to the ON position. If Engine Control Module (ECM) determines intake manifold air temperature is less than 59°F (15°C) by input signal received from intake manifold air temperature sensor, ECM delivers output signal to operate WAIT-TO-START warning light and intake manifold air heater for a preheat cycle.
WAIT-TO-START warning light will remain on until intake manifold air heater preheat cycle is complete. WAIT-TO-START warning light will flash on and off if intake manifold air temperature sensor signal to ECM is not within a specified value and Diagnostic Trouble Code (DTC) will be stored in ECM memory.
WATER-IN-FUEL Warning Light
WATER-IN-FUEL warning light is located on instrument panel, just below tachometer. WATER-IN-FUEL warning light will come on for a short period and then go off as a bulb and wiring circuit test each time ignition switch is turned to the ON position. If Engine Control Module (ECM) determines water exists in fuel/water separator by input signal from Water-In-Fuel (WIF) sensor, ECM will deliver output signal to turn on the WATER-IN-FUEL warning light.
A/C Clutch Relay
The Engine Control Module (ECM) controls A/C compressor operation by controlling ground circuit for A/C clutch relay. ECM 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.
The Engine Control Module (ECM) 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. Automatic Shutdown (ASD) relay may also be referred to as Auto Shutdown (ASD) relay.
These circuits are connected between Engine Control Module (ECM) and Powertrain Control Module (PCM) to allow communication between modules.
Cruise Control System
Engine Control Module (ECM) 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.
Data Link Connector
Engine Control Module (ECM) provides output information at Data Link Connector (DLC) when using scan tool to perform various tests on the ECM and electronic control system. Data link connector is a 16-pin connector located at lower edge of driver's side of instrument panel, just above the accelerator pedal.
Powertrain Control Module (PCM) supplies a 5-volt reference signal to the transmission solenoid assembly for transmission temperature sensor.
Generator Field
Engine Control Module (ECM) provides output signals to generator field for regulating charging system voltage at 12.9-15.0 volts. ECM contains an internal electronic voltage regulator for controlling the charging system voltage.
Generator Light
If Engine Control Module (ECM) senses a low charging system condition, generator light on instrument panel (if equipped) will be turned on. Generator light may also come on momentarily at low idle speed when all accessories are on.
The MIL is located on the instrument panel, just below tachometer 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 switch is turned to the ON position. If Engine Control Module (ECM) receives an incorrect signal or receives no signal from certain sensors or components, ECM will turn on the MIL to warn the driver that a malfunction exists in the electronic system.
Overdrive Indicator Light (A/T Models)
Engine Control Module (ECM) delivers output signal to operate transmission overdrive indicator (O/D OFF) 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 instrument panel, just below the speedometer.
Tachometer
Engine Control Module (ECM) delivers output signal to operate tachometer on instrument panel to indicate engine RPM.
Transmission Overdrive Solenoid (A/T Models)
Engine Control Module (ECM) delivers output signal to transmission overdrive solenoid for controlling transmission overdrive shifts. Transmission overdrive solenoid is located on transmission valve body.
Transmission Relay (A/T Models)
Transmission relay may be referred to as transmission control relay or transmission 12-volt supply relay. Transmission relay ground circuit is controlled by the Engine Control Module (ECM). 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 Temperature Warning Light (A/T Models With Heavy-Duty Transmission)
Engine Control Module (ECM) delivers output signal to turn on transmission temperature warning light if transmission fluid temperature is determined to be greater than 280°F (138°C) by the transmission temperature sensor. Transmission temperature warning light is located on instrument panel, just below the tachometer.
Transmission Torque Converter Clutch Solenoid (A/T Models)
Engine Control Module (ECM) delivers an output signal to operate transmission torque converter clutch solenoid for torque converter lock-up. ECM uses various input signals such as transmission temperature, output shaft speed, central module timer, engine speed, APPS and brake switch position to determine operation of transmission torque converter clutch solenoid. Transmission torque converter clutch solenoid is located on transmission valve body.
Fuel Injection Pump
A camshaft-driven Bosch VP44 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) Fuel injection pump is timed to camshaft gear. fuel injection pump output is controlled by integral Fuel Pump Control Module (FPCM). Because of electronic control, idle speeds and fuel injection pump timing are not adjustable. See ON-VEHICLE ADJUSTMENTS - TRUCKS - DIESEL article. FPCM can operate engine if crankshaft position sensor signal does not exist. Fuel injection occurs near completion of compression stroke for each cylinder.
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.
Fuel transfer pump is located on driver's side of cylinder block, above starter. (Scheme 2) A 12-volt, 12-amp electric vane-type pump supplies low fuel pressure from fuel tank, through fuel heater/fuel filter/water separator 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 will self prime with ignition on for 2 seconds. Fuel transfer pump has 2 modes, 100 percent duty cycle (10 psi) when engine is running and 25 percent duty cycle (7 psi) when engine is cranking.
Fuel Filter/Water Separator
Fuel filter/water separator, located on left side of engine, protects fuel injection pump by removing water and contaminants from fuel. (Scheme 2) Assembly also includes fuel heater and Water-In-Fuel (WIF) sensor.
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.
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 4500 psi (316 kg/cm 2 ). 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. Each fuel injector is connected to fuel injection pump by a high pressure (as much as 17,405 psi) line.
Fuel Injection Timing
Fuel injection pump output is controlled by integral Fuel Pump Control Module (FPCM). Because of electronic control, fuel injection pump timing is not adjustable. See ON-VEHICLE ADJUSTMENTS - TRUCKS - DIESEL article.
Fuel filter/water separator is located on left side of engine and contains fuel heater, Water-In-Fuel (WIF) sensor and drain valve. (Scheme 2) The WIF sensor delivers an input signal to Engine Control Module (ECM) when water exists in fuel filter/water separator. ECM will then turn on WATER-IN-FUEL warning light. WATER-IN-FUEL warning light is located on instrument panel, just below tachometer. The WATER-IN-FUEL warning light informs the 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 in fuel filter/water separator. (Scheme 2) Fuel flows from fuel tank to fuel transfer pump and then to fuel filter/water separator. Fuel heater contains a fuel heater temperature sensor that senses the fuel temperature. When temperature is less than 37-53°F (3-12°C), fuel heater temperature sensor allows current to flow to the fuel heater to warm the fuel. When temperature is more than 67-83°F (19-28°C), fuel heater temperature sensor turns off the current flow to the fuel heater. Voltage to operate fuel heater is provided from ignition switch, through fuel heater relay and to fuel heater. Fuel heater and fuel heater relay are not controlled by Engine Control Module (ECM).
INTAKE MANIFOLD AIR HEATER SYSTEM
Intake manifold air heater is used to warm intake air during cold starting conditions. Heater system consists of 2 relays and 2 grid heaters installed on top of intake manifold. (Scheme 5)
Engine Control Module (ECM) 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. 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 left inner wheelwell, below left side battery. (Scheme 6)
Intake manifold air temperature sensor monitors intake manifold air temperature and delivers an input signal to ECM for controlling intake manifold air heater. Intake manifold air temperature sensor is located in intake manifold. (Scheme 2)and (Scheme 4).
The Data Link Connector (DLC) is a 16-pin connector located at lower edge of driver's side of instrument panel, just above the accelerator pedal. The Engine Control Module (ECM) contains a self-diagnostic system which stores a Diagnostic Trouble Code (DTC) if an incorrect signal or no signal is received from certain sensors or components. DTC may be retrieved from ECM for system diagnosis by using DLC and a scan tool. The DLC also provides a means to communicate with various vehicle control modules, check system operating conditions and to operate various system components.
The MIL is located on the instrument panel, just below tachometer 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 switch is turned to the ON position. If Engine Control Module (ECM) receives an incorrect signal or receives no signal from certain sensors or components, ECM will turn on the MIL to warn the driver that a malfunction exists in the electronic system.
Engine Control Module (ECM) operates transmission overdrive solenoid for controlling transmission overdrive shifts. Transmission overdrive solenoid is located on transmission valve body.
Engine Control Module (ECM) operates transmission torque converter clutch solenoid for torque converter lock-up. ECM uses various input signals such as transmission temperature, output shaft speed, central module timer, engine speed, APPS and brake switch position to determine operation of transmission torque converter clutch solenoid. Torque converter clutch solenoid is located on transmission valve body.