General System Description
ENGINE CONTROL MODULE (ECM)The Engine Control Module (ECM) and Fuel Injection Pump Control Module (FPCM) are used to electrically control the fuel system. The Powertrain Control Module (PCM) does not control the fuel system.
Engine Control Module (ECM) Location:
Fuel Injection Pump Control Module (FPCM) Location:
The ECM is bolted to the left side of the engine behind the fuel filter. It is a separate component and can be serviced. The FPCM is internal to the fuel injection pump and cannot be serviced.
The main function of the ECM and the FPCM is to control the fuel injection system.
The ECM can adapt its programming to meet changing operating conditions. If the ECM has been replaced, flashed or re-calibrated, the ECM must learn the Accelerator Pedal Position Sensor (APPS) idle voltage. Failure to learn this voltage may result in unnecessary diagnostic trouble codes. Refer to ECM Removal/Installation for learning procedures.
The ECM receives input signals from various switches and sensors. Based on these inputs, the ECM regulates various engine and vehicle operations through different system components. These components are referred to as ECM Outputs. The sensors and switches that provide inputs to the ECM are considered ECM Inputs.
NOTE: ECM Inputs:
- Accelerator Pedal Position Sensor (APPS) Volts
- APPS Idle Validation Switches #1 and #2
- Battery voltage
- Camshaft Position Sensor (CMP)
- CCD bus (+) circuits
- CCD bus (-) circuits
- Crankshaft Position Sensor (CKP)
- Data link connection for DRB scan tool
- (FPCM) Fuel Injection Pump Control Module
- Engine Coolant Temperature (ECT) sensor
- Ground circuits
- Intake manifold Air Temperature (IAT) sensor
- Manifold Air Pressure Sensor (Boost Pressure Sensor)
- Oil pressure sensor
- PCM
- Power Take Off (PTO)
- Power ground
- Sensor return
- Signal ground
- Water-In-Fuel (WIF) sensor
NOTE: ECM Outputs:
After inputs are received by the ECM, certain sensors, switches and components are controlled or regulated by the ECM. These are considered ECM Outputs. These outputs are for:
- CCD bus (+) circuits
- CCD bus (-) circuits
- CKP and APPS outputs to the PCM
- Data link connection for DRB scan tool
- Five volt sensor supply
- Fuel injection pump
- Fuel injection pump relay
- (FPCM) Fuel Pump Control Module
- Fuel transfer (lift) pump
- Intake manifold air heater relays #1 and #2 control circuits
- Malfunction indicator lamp (Check engine lamp)
- Oil pressure gauge/warning lamp
- PCM
- Wait-to-start warning lamp
- Water-In-Fuel (WIF) warning lamp
ACCELERATOR PEDAL POSITION SENSOR (APPS)-ECM INPUT
The Accelerator Pedal Position Sensor (APPS) is a linear potentiometer. It provides the Engine Control Module (ECM) with a DC voltage signal proportional to the angle, or position of the accelerator pedal. In previous model years, this part was known as the Throttle Position Sensor (TPS).
Diesel engines used in previous model years used a mechanical cable between the accelerator pedal and the TPS lever. Linkage and bellcranks between the TPS cable lever and the fuel injection pump were also used. Although the cable has been retained with the APPS, the linkage and bellcranks between the cable lever and the fuel injection pump are no longer used.
APPS Assembly Location:
APPS Sensor Location (Rear View):
The APPS assembly is located at the top-left-front of the engine. A plastic cover is used to cover the assembly. The actual sensor is located behind its mounting bracket.
The APPS is serviced (replaced) as one assembly including the lever, brackets and sensor. The APPS is calibrated and permanently positioned to its mounting bracket.
CAUTION: Do not attempt to remove sensor from its mounting bracket as electronic calibration will be destroyed (sensor-to-bracket mounting screws are permanently attached). Two accelerator lever set screws are used to position lever. Do not attempt to alter positions of these set screws as electronic calibration will be destroyed.
BATTERY VOLTAGE-ECM INPUT
The battery voltage input provides power to the Engine Control Module (ECM). It also informs the ECM what voltage level is being supplied by the generator once the vehicle is running.
The battery input also provides the voltage that is needed to keep the ECM memory alive. The memory stores Diagnostic Trouble Code (DTC) messages.
CAMSHAFT POSITION SENSOR (CMP)-ECM INPUT
Camshaft Position Sensor (CMP):
The Camshaft Position Sensor (CMP) contains a hall effect device called a sync signal generator to generate a sync signal.
The sync signal generator detects a machined hole on the rear face of the camshaft drive gear. The signal is used to verify the position of the #1 cylinder during engine operation.
When the leading edge of the machined hole enters the tip of the CMP the interruption of magnetic field causes the voltage to switch high resulting in a signal of approximately 5 volts.
When the trailing edge of the machined hole leaves the tip of the CMP the change of the magnetic field causes the voltage to switch low to 0 volts.
Camshaft Position Sensor (CMP) Location:
The CMP is located below the fuel injection pump. It is attached to the back of the timing gear cover housing.
The CMP is not used for any control of fuel system. It is used only for diagnostic purposes.
CCD BUS (+/-) CIRCUITS-ECM/PCM INPUTS/OUTPUTS
The Engine Control Module (ECM) and the Powertrain Control Module (PCM) send certain signals through the CCD bus circuits. Some of these signals are parallel circuited between the two control modules (ECM and PCM). These signals are used to control certain instrument panel located items and to determine certain identification numbers.
Refer to Instrument Panel and Gauges for additional information.
CRANKSHAFT POSITION SENSOR (CKP)-ECM INPUT
Crankshaft Position Sensor (CKP) Location:
The Crankshaft Position Sensor (CKP) is located on the lower left-rear side of the engine behind the starter motor.
Engine speed and crankshaft position are provided through the CKP. The sensor generates pulses that are the input sent to the Engine Control Module (ECM). The ECM interprets the sensor input to determine the crankshaft position. The ECM then uses this position, along with other inputs, to deter- mine injector firing sequence and fuel timing. The sensor must be powered up by 5 volts to operate.
The sensor is a hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.
Crankshaft Tone Wheel:
The engine crankshaft is equipped with a bolt-on tone wheel. The tone wheel is equipped with 35 teeth and a gap where the 36th tooth should be placed. This missing tooth indicates to the ECM the relative position of cylinder #1 to the Top Dead Center (TDC) position. This does not mean that cylinder #1 is at TDC. When the CKP is aligned with the missing tooth, the missing tooth is 60 degrees away from cylinder #1 TDC position. The teeth cause pulses to be generated when they pass under the sensor. The pulses are the input to the ECM.
ENGINE COOLANT TEMPERATURE (ECT) SENSOR-ECM INPUT
Engine Coolant Temperature Sensor:
The engine coolant temperature sensor is installed into the front of the cylinder head near to the thermostat housing and protrudes into a water jacket. The sensor provides an input voltage to the Engine Control Module (ECM) to monitor coolant temperature. The ECM uses this input along with inputs from other sensors for engine protection, fuel timing and fuel control. As coolant temperature varies, the coolant temperature sensor resistance will change. This change in resistance results in a different input voltage to the ECM.
FUEL TEMPERATURE SENSOR
Two different fuel temperature sensors are used. One of the sensors is located inside of the Bosch VP44 fuel injection pump and is a non-serviceable part. It is used to check fuel temperature within the injection pump and to set a Diagnostic Trouble Code (DTC) if a specific high fuel temperature has been reached. If high temperature has been reached, engine power will be de-rated by the Engine Control Module (ECM).
The other fuel temperature sensor is located in the top of the fuel filter housing and is serviceable (serviceable if replacing the fuel heater). It is used to control the fuel heater element. Refer to Fuel Heater Description and Operation for additional information.
INTAKE MANIFOLD AIR TEMPERATURE (IAT) SENSOR-ECM INPUT
The IAT provides an input voltage to the Engine Control Module (ECM) indicating intake manifold air temperature. The input is used along with inputs from other sensors for engine protection, fuel timing and fuel control. As the temperature of the air-fuel stream in the manifold varies, the sensor resistance changes. This results in a different input voltage to the ECM.
Intake Manifold Air Temperature (IAT) Sensor Location:
The intake manifold air temperature sensor is installed into the rear of the intake manifold with the sensor element extending into the air stream.
MANIFOLD AIR PRESSURE (MAP) SENSOR-ECM INPUT
The MAP sensor reacts to air pressure changes in the intake manifold. It provides an input voltage to the Engine Control Module (ECM). As pressure changes, MAP sensor voltage will change. The change in MAP sensor voltage results in a different input voltage to the ECM. The ECM uses this input, along with inputs from other sensors to provide fuel timing, fuel control and engine protection. Engine protection is used to derate (drop power off) the engine if turbocharger pressure becomes to high.
The MAP sensor is installed into the rear of the intake manifold.
OIL PRESSURE SENSOR (ENGINE)-ECM INPUT
A signal is sent from the engine oil pressure sensor (sending unit) to the Engine Control Module (ECM) relating to engine oil pressure. The ECM monitors this signal and converts it to a pressure value. This value is used by the ECM for the engine protection system.
The pressure signal from the ECM is bussed to the instrument panel oil gauge/lamp via the CCD circuits.
Oil Pressure Sensor (Engine) Location:
The oil pressure sensor is installed into the oil pressure galley on the engine block. It is located below and to the rear of the ECM.
PTO SWITCH SENSE-ECM INPUT
This Engine Control Module (ECM) input is used only on models equipped with aftermarket Power Take Off (PTO) units.
The input is used to tell the ECM that the PTO has been engaged. When engaged, the ECM will disable certain OBD II functions until the PTO has been turned off.
WATER-IN-FUEL (WIF) SENSOR-ECM INPUT
The sensor sends an input to the Engine Control Module (ECM) when it senses water in the fuel filter water separator. As the water level in the filter/separator increases, the resistance across the WIF sensor decreases. This decrease in resistance is sent as a signal to the ECM and compared to a high water standard value. Once the value reaches 30 to 40 kilohms, the ECM will activate the water-in-fuel warning lamp through CCD bus circuits. This all takes place when the ignition key is initially put in the ON position. The ECM continues to monitor the input at the end of the intake manifold air heater post-heat cycle.
Water-In-Fuel Sensor Location:
The WIF sensor is located at the bottom of the fuel filter/water separator canister.
FUEL INJECTION PUMP RELAY-ECM OUTPUT
The Engine Control Module (ECM) energizes the electric fuel injection pump through the fuel injection pump relay. Battery voltage is applied to the fuel injection pump relay at all times. When the key is turned ON, the relay is energized when a 12-volt signal is provided by the ECM. When energized, 12-volts is supplied to the Fuel Pump Control Module. The Fuel Pump Control Module is located on the top of the fuel injection pump and is non-serviceable.
The fuel injection pump relay is located in the Power Distribution Center (PDC). Refer to label under PDC cover for relay location.
INTAKE MANIFOLD AIR HEATER ELEMENTS
The air heater elements are used to heat incoming air to the intake manifold. This is done to help engine starting and improve driveability with cool or cold outside temperatures.
Electrical supply for the 2 air heater elements is controlled by the Engine Control Module (ECM) through the 2 air heater relays. Refer to Intake Manifold Air Heater Relays for more information.
Two heavy-duty cables connect the 2 air heater elements to the 2 air heater relays. Each of these cables will supply approximately 95 amps at 12 volts to an individual heating element within the heater block assembly.
Air Heater Elements Location:
The intake manifold air heater element assembly is located in the top of the intake manifold.
Refer to the Powertrain Diagnostic Procedures for an electrical operation and complete description of the intake heaters, including pre-heat and post-heat cycles.
INTAKE MANIFOLD AIR HEATER RELAYS-ECM OUTPUT
The Engine Control Module (ECM) operates the 2 heating elements through the 2 intake manifold air heater relays.
Intake Manifold Air Heater Relays Location:
The 2 relays are located in the engine compartment, attached to the left inner fender below the left battery.
Refer to the Powertrain Diagnostic Procedures for an electrical operation and complete description of the intake heaters, including pre-heat and post-heat cycles.
WAIT-TO-START WARNING LAMP-ECM OUTPUT
The wait-to-start warning lamp is turned on and off by the Engine Control Module (ECM) based on the intake manifold air temperature sensor input. The lamp is located on the instrument panel.
The lamp is turned on when the key is first activated. If the ECM reads intake manifold air temperature below 19°C (66°F), it will turn the wait-to-start warning lamp on for the air heater pre-heat cycle. The lamp stays on until the pre-heat cycle is over.
Refer to the Powertrain Diagnostic Procedures for electrical operation and complete description of the intake heaters, including pre-heat and post-heat cycles.
WATER-IN-FUEL WARNING LAMP-ECM INPUT
The Engine Control Module (ECM) turns on the water-in-fuel warning lamp if water is detected in the diesel fuel. The water-in-fuel warning lamp is located in the instrument panel. The lamp will illuminate for about two seconds each time the key is initially turned to the ON position as a bulb check.
If the lamp continues to be illuminated, it signals an immediate need for service. Refer to Fuel Filter Water Separator Removal/installation for water draining procedures.
Also refer to Water-In-Fuel Sensor-ECM Input for additional information.