Part 2
Electronic Engine Controls
DIFFERENTIAL PRESSURE FEEDBACK-ELECTRONIC/MANIFOLD ABSOLUTE PRESSURE SENSOR (DPFE/MAP (manifold absolute pressure))
This pressure transducer monitors the pressure differential on either side of an orifice in the EGR (exhaust gas recirculation) system flow path and transmits that information to the ECM (engine control module). The pressure drop measured across this orifice is used to estimate the flow rate of recirculated exhaust gas. An Electronic Vacuum Regulator (EVR) is used to control the vacuum signal to the EGR (exhaust gas recirculation) valve based on the electrical signal from the ECM (engine control module). The ECM (engine control module) monitors the
EGR (exhaust gas recirculation) level based on the feedback from the DPFE/MAP (manifold absolute pressure) transducer, which creates a closed loop system.
EXHAUST GAS RECIRCULATION VALVE (EGR)
The EGR (exhaust gas recirculation) Valve is a PWM (pulse width modulation) controlled valve that allows burned exhaust gas to be recirculated back into the engine. Since exhaust gas has much less oxygen than air, it is basically inert. It takes the place of air in the cylinder and reduces combustion temperature. As the combustion temperature is reduced, so are the oxides of nitrogen (NOx) emissions.
SPEED CONTROL
The V6 ECM (engine control module) incorporates a speed control function. The EMS uses a set of resistive ladders to interface with the driver speed control requirements. The speed control is operated from the steering wheel mounted switches. There are three illuminated rocker switches on a resistive ladder. For additional information, refer to Speed Control Description and Operation
The speed control does not have a master switch, it is enabled by pressing the set switch.
GENERATOR
The Generator has a multi function voltage regulator for use in a 14V charging system with 6÷12 zener diode bridge rectifiers.
The ECM (engine control module) monitors the load on the electrical system via PWM (pulse width modulation) signal and adjusts the generator output to match the required load. The ECM (engine control module) also monitors the battery temperature to determine the generator regulator set point. This characteristic is necessary to protect the battery; at low temperatures battery charge acceptance is very poor so the voltage needs to be high to maximize any recharge ability, but at high temperatures the charge voltage must be restricted to prevent excessive gassing of the battery with consequent water loss.For additional information, refer to Generator
The Generator has a smart charge capability that will reduce the electrical load on the Generator reducing torque requirements, this is implemented to utilize the engine torque for other purposes. This is achieved by monitoring three signals to the ECM (engine control module):
- Generator sense (A sense), measures the battery voltage at the CJB (central junction box).
- Generator communication (Alt Com) communicates desired Generator voltage set point from ECM (engine control module) to Generator.
- Generator monitor (Alt Mon) communicates the extent of Generator current draw to ECM (engine control module). This signal also transmits faults to the ECM (engine control module) which will then sends a message to the instrument pack on the CAN (controller area network) bus to illuminate the charge warning lamp.
FUEL INJECTORS
The ECM (engine control module) controls six fuel injectors located on the cylinder head. The injectors are fed from a common fuel rail as part of a 'returnless' fuel system.
Fuel rail pressure is constant at 4.5 bar (59 psi) and is regulated by a regulator that is integral to the fuel pump module. The ECM (engine control module) monitors the output power stages of the injector drivers for electrical faults. The injector has a default resistance of 14.5 Ohms at 20 Degrees Celsius.For additional information, refer to Fuel Charging and Controls
SPARK PLUGS
It is essential that only factory-approved spark plugs be used in service. DO NOT attempt to use 'equivalent' spark plugs. Use of unapproved spark plugs may cause the misfire detection system to malfunction, and the ECM (engine control module) to store misfire faults.
IGNITION COILS
The Land Rover V6 engine is fitted with ignition coils that are driven directly by the ECM (engine control module). The coils are mounted on top of the inlet manifold and are connected to the spark plugs by High Tension (HT) leads. The positive supply to the coil is fed from fuse 19 in the BJB (battery junction box). Each coil contains a power stage to trigger the primary current. The ECM (engine control module) sends a signal to each of the coils power stage to trigger the power stage switching. Each bank has a feedback signal that is connected to each power stage. If the coil power stage fails the feedback signal is not sent, causing the ECM (engine control module) to store a fault
code.
FUEL PUMP RELAY
The V6 engine has a return less fuel system. The system pressure is maintained at a constant 4.5 bar , with no reference to intake manifold pressure. The fuel is supplied to the injectors from a fuel pump located within the fuel tank. The electrical supply to this fuel pump is controlled by the ECM (engine control module) via the fuel pump relay, in the event of a vehicle impact the ECM (engine control module) will receive a crash signal from the restraints control module and will cut the power supply to the fuel pump relay. The fuel system is pressurized as soon as the ECM (engine control module) is powered up, the pump is then switched off until engine start has been achieved.
The fuel pump relay is located in the CJB (central junction box). The Fuel pump is contained within the fuel tank.For additional information, refer to Fuel Tank and Lines Fuel Tank and Lines
VISCOUS FAN CONTROL
The ECM (engine control module) controls an electronically controlled viscous coupled fan to provide engine cooling. The ECM (engine control module) supplies the fan with a PWM (pulse width modulation) signal that controls the amount of slippage of the fan, thus providing the correct amount of cooling fan speed and airflow. The EMS uses a Hall Effect sensor to determine the fan speed.
STARTER RELAY
The starter relay is supplied with power from fuseable link 19 in the Battery Junction Box.
The ECM (engine control module) controls the starter relay by supplying a 12 volt signal to the relay coil when the ignition is in crank position. This relies on the transmission gear position being either P or N.
CONDENSER FAN CONTROL
The ECM (engine control module) receives CAN (controller area network) messages from the ATC (automatic temperature control) control module for idle speed adjustment and for cooling fan.
AirConCoolingRequest
This signal defines the level of cooling (from engine cooling fan(s)) required by the ATC (automatic temperature control) system. Calibration within the EMS determines the fan speed required, and which fans will be used, at each requested level.
AirConIdleSpeedRequest
This signal defines whether or not an increase in the engine idle speed is required by the ATC (automatic temperature control) system. The amount of idle speed increase is defined in the EMS calibration.
IMT (intake manifold tuning) valve
The IMT (intake manifold tuning) valve moves a plate within the inlet manifold to allow or block sonic pulses between the split manifold halves. This, in effect, extends the inlet tracts for better low rpm torque. The IMT (intake manifold tuning) valve is a two position valve and is either fully open or fully closed.For additional information, refer to Intake Air Distribution and Filtering Intake Air Distribution and Filtering
ECM (engine control module) ADAPTATIONS
The ECM (engine control module) has the ability to adapt the values it uses to control certain outputs. This capability ensures the EMS can meet emissions legislation and improve the refinement of the engine throughout its operating range.
The components which have adaptations associated with them are:
- The APP (accelerator pedal position) sensor
- The HO2S
- The MAF (mass air flow)/IAT (intake air temperature) sensor
- The CKP (crankshaft position) sensor
- Electric throttle body.
UHEGO/HEGO and MAF (mass air flow)/IAT (intake air temperature) Sensor
There are several adaptive maps associated with the fueling strategy. Within the fueling strategy the ECM (engine control module) calculates short-term adaptations and long term adaptations. The ECM (engine control module) will monitor the deterioration of the HO2S over a period of time. It will also monitor the current correction associated with the sensors.
The ECM (engine control module) will store a fault code in circumstances where an adaption is forced to exceed its operating parameters. At the same time, the ECM (engine control module) will record the engine speed, engine load and intake air temperature.
CKP (crankshaft position) Sensor
The characteristics of the signal supplied by the CKP (crankshaft position) sensor are learned by the ECM (engine control module). This enables the ECM (engine control module) to set an adaption and support the engine misfire detection function. Due to the small variation between different flywheels and different CKP (crankshaft position) sensors, the adaption must be reset if either component is renewed, or removed and refitted. It is also necessary to reset the flywheel adaption if the ECM (engine control module) is renewed or replaced. The ECM (engine control module)
supports four flywheel adaptations for the CKP (crankshaft position) sensor. Each adaption relates to a specific engine speed range. The engine speed ranges are detailed in the table below:
Misfire Detection
Legislation requires that the ECM (engine control module) must be able to detect the presence of an engine misfire. It must be able to detect misfires at two separate levels. The first level is a misfire that could lead to the vehicle emissions exceeding 1.5 times the Federal Test Procedure (FTP) requirements for the engine. The second level is a misfire that may cause catalyst damage.
The ECM (engine control module) monitors the number of misfire occurrences within two engine speed ranges. If the ECM (engine control module) detects more than a predetermined number of misfire occurrences within either of these two ranges, over two consecutive journeys, the ECM (engine control module) will record a fault code and details of the engine speed, engine load and engine coolant temperature. In addition, the ECM (engine control module) monitors the number of misfire occurrences that happen in a 'window' of 200 engine revolutions. The misfire occurrences are assigned a weighting according to their likely impact on the catalysts. If the number of misfires exceeds a certain value, the
ECM (engine control module) stores catalyst-damaging fault codes, along with the engine speed, engine load and engine coolant temperature.
The signal from the crankshaft position sensor indicates how fast the poles on the flywheel are passing the sensor tip. A sine wave is generated each time a pole passes the sensor tip. The ECM (engine control module) can detect variations in flywheel speed by monitoring the sine wave signal supplied by the crankshaft position sensor.
By assessing this signal, the ECM (engine control module) can detect the presence of an engine misfire. At this time, the ECM (engine control module) will assess the amount of variation in the signal received from the crankshaft position sensor and assigns a roughness value to it. This roughness value can be viewed within the real time monitoring feature, using T4. The ECM (engine control module) will evaluate the signal against a number of factors and will decide whether to count the occurrence or ignore it. The ECM (engine control module) can assign a roughness and misfire signal for each cylinder, (i.e. identify which cylinder is misfiring).
T4
Diagnostics
The ECM (engine control module) stores faults as DTC (diagnostic trouble code), referred to as 'P' codes. The 'P' codes are defined by OBD (on-board diagnostic)legislation and, together with their associated environmental and freeze frame data, can be read using a third party scan tool or T4. T4 can also read real time data from each sensor, the adaptive values currently being employed and the current fueling, ignition and idle settings.
CENTRAL JUNCTION BOX
The Central Junction box is used to initiate the power up and power down routines within the ECM (engine control module). When the ignition is turned on, 12V is applied to the Ignition Sense input to pin 30 of connector C0635. The ECM (engine control module) then starts its power up routines and turns on the ECM (engine control module) main relay.
When the ignition is turned OFF the ECM (engine control module) will maintain its powered up state for several seconds (this may be up to 20 minutes in extreme cases when cooling fans are required) while it initiates its power down routine and on completion will turn off the ECM (engine control module) main relay.
POWER SUPPLIES
The ECM (engine control module) requires a permanent battery level voltage supply and a switched battery level voltage supply. The switched voltage supply is controlled by the ECM (engine control module) via a relay based on the condition of the Central Junction Box input (key position 2).
At key "OFF", the ECM (engine control module) will maintain the switched supply active until internal self checks have been completed. The Main Supply fuse is located in the engine compartment fuse box.
PURGE VALVE
Purge Valve and Hoses
To meet increasing legislation in fuel evaporative loss the Evaporative Emissions Loss Control System has been introduced to minimize the evaporative loss of fuel vapor from the fuel system to the atmosphere. This is achieved by venting the fuel system through a vapor trap (charcoal cannister). The charcoal acts like a sponge and stores the vapor until the canister is purged under the control of the ECM (engine control module).
The charcoal canister is connected with the inlet manifold, after the throttle body, via a purge valve. This valve is opened and closed according to a PWM (pulse width modulation) signal from the ECM (engine control module). The canister is purged by drawing clean air through the charcoal, which carries the hydrocarbons into the engine where they are burnt. To maintain driveability and emission control purging must be closely controlled as a 1% concentration of fuel vapor from the canister in the air intake may shift the air/fuel ratio by as much as 20%. Purging must be carried out at regular intervals, to regenerate the charcoal, as its storage capacity is limited, and is cycled with the Fueling Adaption, as both cannot be active at the same time.
The ECM (engine control module) alters the PWM (pulse width modulation) signal to the purge valve to control the rate of purging of the canister. The purging of the canister is done in a controlled manner in order to maintain the correct Stoichiometric air/fuel mixture for the engine. It also ensures the canister itself is purged frequently enough to prevent fuel saturation of the charcoal leading to an excessive build up of fuel vapor (and hence vapor pressure) in the system which could increase the likelihood of vapor leaks.For additional information, refer to Evaporative Emissions Description and Operation