Part 1

Electronic Engine Controls

[Denso] Electronic Engine Controls Component Location Sheet 1 Of 2:

[Denso] Electronic Engine Controls Component Location Sheet 2 of 2:

[Denso] EMS Control Diagram Sheet 1 of 2:

GENERAL
The V6 4.0 Liter engine is controlled by a Engine Control Module (ECM) manufactured by DENSO. The Engine Management System (EMS) controls the following:
^ Engine fuelling
^ Ignition timing
^ Closed loop fuelling
^ Knock control
^ Idle speed control
^ Emission control
^ On Board Diagnostic
^ Interface with the immobilization system
^ Cruise control

ENGINE CONTROL MODULE (ECM)

Engine Control Module:

The ECM is located in the E-Box in the plenum area on the passenger side of the engine compartment attached to the bulkhead.

Inputs
The ECM has the following inputs:
^ Central Junction Box
^ Engine Coolant Temperature
^ Brake Switch
^ Manifold Absolute Pressure
^ Accelerator Pedal Position 1
^ Accelerator Pedal Position 2
^ Throttle Position 1
^ Throttle Position 2
^ Engine cooling fan Speed
^ Engine speed and position sensor (crankshaft sensor)
^ Camshaft position sensor
^ Engine Oil Temperature
^ Inlet Air Temperature sensor (integrated into MAF)
^ Mass Air Flow sensor (MAF)
^ Knock sensors (2)
^ Cruise Control Switches (resistive ladders)
^ Oxygen sensors (4)
^ Vehicle Speed (via CAN)
^ EGR Differential Pressure
^ EGR MAP
^ Generator Monitor

Outputs
The ECM outputs to the following:
^ Throttle Actuator
^ Ignition coils (6)
^ Oxygen sensor heaters (4)
^ Fuel injectors (6)
^ EGR Valve
^ Inlet Manifold Tuning Valve (IMTV)
^ Purge Valve
^ Fuel pump relay
^ Starter Relay
^ Air conditioning condenser fan module (CAN)
^ EMS Main Relay
^ Viscous Fan Control
^ Generator Control

The ECM controls the engine fuelling by providing sequential fuel injection to all cylinders. Ignition is controlled by a direct ignition system, provided by six plug top coils. The ECM is able to detect and correct for ignition knock on each cylinder and adjust the ignition timing for each cylinder to achieve optimum performance.

The ECM uses a torque-based strategy to generate the torque required by the driver and other vehicle ECU's. The EMS uses various sensors to determine the torque required from the engine. These include:
^ Mass Air Flow meter
^ Accelerator Pedal Position sensor
^ Engine temperatures
^ Oxygen sensors

The EMS processes these signals and decides how much torque to generate. Torque is then generated by using various actuators to supply air, fuel and spark to the engine (electronic throttle, injectors, coils, etc.) The EMS also interfaces with other vehicle ECU's, via CAN, to obtain additional information, these include
^ ABS control module
^ TCM
^ Transfer box control module

Pin No. 1 - 7:

Pin No. 8 - 53:

Pin No. 54 - 96:

ECM Connector C0635 Pin Out Table

Pin No. 1 - 35:

ELECTRONIC THROTTLE

Electronic Throttle:

The V6 engine torque is regulated via an electronic throttle body which is located on the intake manifold in the engine compartment. An Accelerator Pedal Position sensor (APP) determines the driver demand to control throttle opening. This value is input into the EMS and the throttle is opened to the correct angle by means of an electric motor integrated into the throttle body. Sensors in the throttle body are used to determine the position of the throttle plate and the rate of change in its angle. A software strategy within the ECM enables the throttle position to be calibrated each ignition cycle. When the ignition is turned 'ON', the ECM opens and closes the throttle fully, thus performing a self-diagnostic and calibration. The throttle body is connected to the ECM via a pair of twisted wires to avoid electrical interference.

C0175 Electronic Throttle Pin Out Table

Pin No. 1 - 6:

ACCELERATOR PEDAL POSITION SENSOR (APP)

Accelerator Pedal Position Sensor:

The Accelerator Pedal Position Sensor (APP) is used in conjunction with the Electronic Throttle Body to provide a drive-by-wire system. The sensor is a resistive type. Sensors in the accelerator pedal are used to determine the driver's request for vehicle speed, acceleration and deceleration. This value is input into the EMS and the throttle is opened to the correct angle by means of an electric motor integrated into the throttle body.

The APP sensor signals are checked for range, and for plausibility. Two separate reference voltages are supplied to the pedal. If one sensor fails, the other can be used as a 'limp - home' input.

The wires that connect the ground and signal from both potentiometers to the EMS are twisted together into two pairs, avoiding having to use a screen wire.

If signal failure occurs, the ECM enters limp home mode. The APP Sensor is located at the accelerator pedal.

C0787 APP Sensor Connector Pin Out Table

Pin No. 1 - 8:

OXYGEN SENSORS

Oxygen Sensor-Upstream:

Oxygen Sensor-Downstream:

There are four oxygen sensors located in the exhaust system. Two upstream (UHEGO) before the catalytic converter and two down stream (HEGO) after the catalytic converter. The sensors monitor the level of oxygen in the exhaust gases and is used to control the fuel/air mixture. Positioning a sensor in the stream of exhaust gasses from each bank enables the ECM to control the fuelling on each bank independently of the other, allowing much closer control of the air / fuel ratio and catalyst conversion efficiency.

The Oxygen Sensor needs to operate at high temperatures in order to function correctly. To achieve the high temperatures required, the sensors are fitted with heater elements that are controlled by a PWM signal from the ECM. The heater elements are operated immediately following engine start and also during low load conditions when the temperature of the exhaust gases is insufficient to maintain the required sensor temperatures. A non-functioning heater delays the sensor s readiness for closed loop control and influences emissions. The PWM duty cycle is carefully controlled to prevent thermal shock to cold sensors.

UHEGO (Universal Heated Exhaust Gas Oxygen) sensors also known as Linear or 'Wide Band' sensors produces a constant voltage, with a variable current that is proportional to the oxygen content. This allows closed loop fuelling control to a target lambda, i.e. during engine warm up (after the sensor has reached operating temperature and is ready for operation). This improves emission control.

The HEGO sensor uses Zirconium technology that produces an output voltage dependant upon the ratio of exhaust gas oxygen to the ambient oxygen. The device contains a Galvanic cell surrounded by a gas permeable ceramic, the voltage of which depends upon the level of O2 defusing through. Nominal output voltage of the device for l =1 is 300 to 500m volts. As the fuel mixture becomes richer (l<1) the voltage tends towards 900m volts and as it becomes leaner (l>1) the voltage tends towards 0 volts. Maximum tip temperature is 1,000 Degree Celsius for a maximum of 100 hours.

Sensors age with mileage, increasing their response time to switch from rich to lean and lean to rich. This increase in response time influences the ECM closed loop control and leads to progressively increased emissions. Measuring the period of rich to lean and lean to rich switching monitors the response rate of the upstream sensors.

Diagnosis of electrical faults is continually monitored in both the upstream and downstream sensors. This is achieved by checking the signal against maximum and minimum threshold, for open and short circuit conditions.

Oxygen sensors must be treated with the utmost care before and during the fitting process. The sensors have ceramic material within them that can easily crack if dropped / banged or over-torqued. The sensors must be torqued to the required figure, (40-50 Nm), with a calibrated torque wrench. Care should be taken not to contaminate the sensor tip when anti-seize compound is used on the thread.

Failure Modes
Mechanical fitting & integrity of the sensor.
^ Sensor open circuit / disconnected.
^ Short circuit to vehicle supply or ground.
^ Lambda ratio outside operating band.
^ Crossed sensors Bank A & B.
^ Contamination from leaded fuel or other sources.
^ Change in sensor characteristic.
^ Harness damage.
^ Air leak into exhaust system.

Failure Symptoms
^ Default to Open Loop fuelling for the particular cylinder bank
^ High CO reading.
^ Strong smell of H2S (rotten eggs) till default condition.
^ Excess Emissions.

It is possible to fit front and rear sensors in their opposite location. However the harness connections are of different gender and color to ensure that the senors cannot be incorrectly connected. In addition to this the upstream sensors have two holes in the sensor tip, whereas the down stream sensors have four holes in the sensor tip for the gas to pass through.

KNOCK SENSORS

Knock Sensors:

The ECM uses active knock control, which serves to prevent engine damaging pre-ignition or detonation under all operating conditions enabling the engine to operate without additional safety margins. For the ECM to be able to determine the point at which a cylinder is pre-detonating, 2 piezo-ceramic sensors are mounted on the engine block. Each sensor monitors engine knock by converting the engine block noise into a suitable electrical signal, which is then transmitted back to the ECM via a twisted pair cable. The signal is then processed within the ECM to identify the data that characterizes knocking.

This information is compared to known signal profiles to determine whether knock is present. If so, the closed loop control system then retards the ignition on that cylinder, for a number of cycles, after which it gradually moves back towards its original setting.

Failure Symptoms
The following describes the failure symptoms of the knock sensors:
^ Knock control disabled and a default safe ignition map are used.
^ Possible rough running and reduced engine performance.

One sensor is located in the center of the engine valley and the other is located on the front RH side of the cylinder block.

CRANKSHAFT SPEED AND POSITION SENSOR

Crankshaft Speed And Position Sensor:

The Crankshaft Position Sensor (CKP) is located on the top of the transmission bell housing just to the left of the center line with the sensor tip adjacent to the flywheel rim. The sensor is a variable reluctance type with a resistance of 1100 Ohms ± 150 Ohms.

The sensor produces the signal which enables the ECM to determine the angle of the crankshaft, and the engine RPM. From this, the point of ignition, fuel injection, etc. is calculated. If the signal wires are reversed a 3 ° advance in timing will occur, as the ECM uses the falling edge of the signal waveform as its reference / timing point for each tooth.

The sensor picks up its signal from a reluctor ring machined into the diameter of the drive plate. The reluctor ring has 36 teeth at 10 ° intervals and 3 ° wide. One of the teeth is removed to provide a reference mark which is 60 ° BTDC No.1 cylinder.

The sensor operates by generating an output voltage caused by the change in magnetic field that occurs as the teeth pass in front of the sensor. The output voltage varies with the speed of the teeth passing the sensor. The higher the engine speed, the higher the output voltage.

The ECM transmits the engine speed over the CAN bus.

If the CKP sensor fails while the engine is running the engine will stall, misfire or run poorly and a relevant fault code will be stored. If the engine is not running when a fault occurs then the engine will not start.

CAMSHAFT POSITION SENSOR (CMP)

Camshaft Position Sensor:

The Camshaft Position Sensor (CMP) is a variable reluctance type sensor located at the front of the engine in the valve cover above number 4 cylinder.

The CMP sensor produces one pulse for every two engine revolutions. The sensor picks up on a reluctor on the LH camshaft.

ENGINE COOLANT TEMPERATURE SENSOR

Engine Coolant Temperature Sensor:

The Engine Coolant Temperature sensor (ECT) is a Negative Temperature Coefficient (NTC) type sensor. As coolant temperature rises the resistance of the sensor falls.

The sensor is located at the front of the engine behind and below the throttle body.

Should the sensor fail the ECM use the oil temperature sensor signal as a backup coolant temperature signal.

ENGINE OIL TEMPERATURE SENSOR

Engine Oil Temperature Sensor:

Oil temperature is monitored through a level sensor mounted in the engine sump.

The sensor operates in the range -40 TO 150 degree Celsius.

MASS AIR FLOW /INLET AIR TEMPERATURE SENSOR (MAF/IAT)

Mass Air Flow/Inlet Air Temperature Sensor:

The MAF and IAT sensor is located in the air duct between the air filter and throttle body.

The air mass flow is determined by the cooling effect of inlet air passing over a hot film element contained within the device. The higher the air flow the greater the cooling effect and the lower the electrical resistance of the element. The signal from the device is then calculated by the ECM to determine the Air Mass Flow into the engine.

The measured air mass flow is used in determining the fuel quantity to be injected in order to maintain the stoichiometric air/fuel mixture required for correct operation of the engine and exhaust catalysts. Should the device fail there is a software backup strategy that will be evoked once a fault has been diagnosed.

The Inlet Air Temperature (IAT) sensor is integrated into the Mass Air Flow meter. It is a temperature dependent resistor (thermistor), i.e. the resistance of the sensor varies with temperature. This thermistor is a negative temperature coefficient (NTC) type element meaning that the sensor resistance decreases as the sensor temperature increases. The sensor forms part of a voltage divider chain with an additional resistor in the ECM. The voltage from this network changes as the sensor resistance changes, thus relating the air temperature to the voltage measured by the ECM.

The fixed default value for air temperature is 35 degree C