Part 2

Electronic Engine Controls

Engine Oil Level/Temperature Sensor





The engine oil level/temperature sensor is located on the underside of the engine and is secured in the engine oil pan with 3 screws and is sealed with an O-ring seal. The ECM supplies the sensor with a 5V reference voltage and two wires supply the temperature and oil level signals back to the ECM.
Two types of engine oil level/temperature sensor are used. On earlier models a capacitive oil level sensor is fitted and was replaced by an ultrasound level sensor on later models. The principle of the temperature sensor is the same in both sensor types. The sensors can be identified by differences in the sensor housings; the capacitive sensor has the electrical connector moulded square to the base of the sensor, the ultrasonic sensor has the connector moulded at a slight angle to the base of the sensor.
The ECM uses both the oil level and temperature signals to calculate the oil level. Temporary oil level changes caused by hill driving or cornering are taken into account by the ECM using additional information such as vehicle speed and engine load.

Engine Oil Level Sensor - Capacitance Type
The engine oil level sensor comprises two capacitive gauge elements. These measure the resistance to electrical current passing through the engine oil.
There are two capacitors, one measuring the permittivity of the oil and a second with two plates set vertically measuring the height. The second capacitor will have a proportion of oil and air between the plates and since the permittivity of air is different to that of oil, the permittivity reading will change as the level of oil decreases and the air between the plate gap increases. This permittivity reading is compared to that of the oil (taken by the first capacitor) and an oil level is derived.

Engine Oil Level Sensor - Ultrasound Type
The engine oil level sensor uses an ultrasonic pulse, which is reflected back from the surface of the oil. The time it takes for this signal to return to the sensor is turned into a PWM signal and is sent to the ECM. The ECM determines the time taken for the ultrasonic pulse signal to be received and calculates it into an oil level figure.

Engine Oil Temperature Sensor
The engine oil temperature sensor is a Positive Temperature Co-efficient (PTC) thermistor element. The element resistance increases as the sensor temperature decreases. The ECM supplies the sensor with a 5V reference voltage and a ground and measures the returned signal as a temperature. A low oil temperature will result in a low voltage being returned to the ECM and high oil temperature will return a high voltage reading.
The ECM monitors the engine oil level/temperature sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. If the sensor fails, the ECM uses the engine coolant temperature sensor signal value as a substitute.

Manifold Absolute Pressure (MAP) Sensor





The MAP sensor is located in the lower part of the intake manifold. The MAP sensor measures the absolute pressure in the intake manifold. The sensor is a semi-conductor type sensor which responds to pressure acting on a membrane within the sensor, altering the output voltage. The sensor receives a 5V reference voltage and a ground from the ECM and returns a signal of between 0.5 - 4.5V to the ECM. A low pressure returns a low voltage signal to the ECM and a high pressure returns a high voltage.
The MAP sensor detects quick pressure changes in the intake manifold after the electric throttle. The signal is used in conjunction with the MAF sensor signal to calculate the injection period.
The ECM monitors the engine MAP sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system. If the sensor fails, the ECM uses the MAF/IAT sensor signal value as a substitute.

Electric Throttle





The electric throttle is located at the entrance of the intake manifold and is secured to the manifold with four Torx head bolts. The throttle also provides for the connection of the air cleaner housing outlet pipe which is secured to the throttle body with a clip.
The electric throttle comprises the throttle body, a round throttle disc which is actuated by a damper motor and a throttle position sensor. The electric throttle is controlled by the ECM and receives positional signals from the TP sensor. If a failure of the motor occurs, the throttle disc is returned to its closed position by the springs, with limited engine speed available to the driver.

Spindle Damper Motor
The motor is a DC damper motor which drives a gear wheel and two springs; one for opening and one for closing. The motor rotates the spindle to which the throttle disc is attached. PWM signals from the ECM control the damper motor to adjust the position of the throttle disc, regulating the amount of air entering the inlet manifold for combustion.
Movement of the motor is achieved by changing the polarity of the power supply to the DC motor, allowing it to be operated in both directions. The throttle disc and the motor has two maximum positions; throttle disc closed which allows minimal air flow through the electric throttle into the intake manifold and throttle disc open which allows maximum air flow into the intake manifold.

Throttle Position (TP) Sensor
The TP sensor is housed in the electric throttle assembly and is used to check the position of the throttle disc. Two permanent magnets in the sensor connected to the throttle disc affect two Hall effect sensors. As the spindle is rotated the magnets rotate around the Hall effect sensors and produce offset analogue signals back to the ECM. The ECM compares these signals to stored values to ensure that they show an accurate throttle disc position. The offset signals are that one Hall effect sensor produces a higher voltage as the throttle angle increases and the other sensor produces a lower voltage as the throttle angle increases.
The ECM performs a self test and a calibration routine on the throttle disc position at each ignition cycle. This is achieved by the ECM powering the damper motor to fully close the throttle disc and then fully open the throttle disc.
The ECM monitors the DC damper motor and the TP sensor for faults and can store fault related codes. These can be retrieved using a Land Rover approved diagnostic system.

Accelerator Pedal Position (APP) Sensor





The APP sensor is located on the accelerator pedal. The sensor comprises a plastic housing which contains two potentiometers and an analogue/digital converter. The potentiometers are connected to a common shaft which is actuated by movement of the accelerator pedal.
The APP sensor provides the ECM and the CJB with information relating to the position of the accelerator pedal. The ECM uses this information to actuate the damper motor in the electric throttle assembly to move the throttle disc to the correct angle in relation to the pedal position.
The APP sensor receives a fused 12V supply from the CJB, which is controlled by the ignition relay in the BJB. The CJB also provides the sensor with a ground. The sensor provides two outputs; the analogue output is transmitted directly to the CJB, which in turn issues the signal to the ECM on the CAN bus, the second output is the Pulse Width Modulation (PWM) signal which is transmitted directly to the ECM. Both the analogue and PWM signals transmit the same positional information.
The ECM uses the PWM signal to calculate the required position of the electric throttle disc in the electric throttle. In the event of a failure of the PWM signal, the ECM uses the analogue signal received from the CJB as a replacement. If the analogue signal is also incorrect or missing, the ECM limits the maximum engine speed to 2000 rpm.
The PWM and the analogue signal are used for diagnosing faults with the APP sensor. If the ECM detects a difference between the analogue and PWM signals a fault code is stored. The ECM will use the signal with the lowest value for electric throttle control. The APP sensor position and any stored fault codes can be read using a Land Rover approved diagnostic system.

Heated Oxygen (HO2S) Sensors





Four HO2S are used by the ECM to measure the oxygen content of the exhaust gasses leaving the engine. Two upstream sensors measure the gasses before they pass through the catalytic converter and two additional downstream sensors measure the gasses after they have passed through the catalytic converter.
The HO2S receive a fused power supply from the main relay in the BJB. Each HO2S is also connected to the ECM on three wires which provide a PWM control of the sensor heating coil, a ground and a signal line.

HO2S Preheating
The HO2S (often referred to as a Lambda sensor) only operates efficiently at temperatures above 300°C (572°F). The normal operating temperature is between 300°C and 850 °C (572°F and 1562°F) and the HO2S is electrically preheated so it reaches the optimum working temperature quickly. Another reason for the preheating is to maintain a normal operating temperature to prevent condensation which could damage the sensor.
The sensor heating coil is a PTC resistor. The heating coil is supplied with battery voltage via the main relay and provided with a ground by the ECM. When the ECM provides the ground the current will pass through the coil. When the sensor is cold, the resistance through the PTC resistor is low and a high current will pass through the coil. The ECM provides a PWM ground initially. As the PTC resistor heats up the resistance increases reducing the current flow. This is sensed by the ECM which gradually reduces the PWM ground to a continuous ground.
The coil is heated immediately following an engine start for a period of approximately 20 seconds and also during low load conditions when the temperature of the exhaust gasses is insufficient to maintain the optimum sensor temperature. The ECM controls the application of the PWM signal to prevent sensor damage due to thermal shock caused by the sensor heating too quickly. The ECM can diagnose faults in the heater coil and record fault codes which can be retrieved using a Land Rover approved diagnostic system.

Upstream HO2S
Two upstream HO2S are used and are located in each exhaust manifold, between the engine and the catalytic converter. The HO2S comprises a solid electrolyte Zirconium dioxide cell surrounded by a gas permeable ceramic. The output voltage from the sensor is dependent on the level of O passing through the permeable ceramic coating. Nominal voltage for lambda=1 is 300 to 500mV. As the fuel/air mixture becomes richer (lambda<1) the voltage rises to up to 900mV. As the mixture becomes weaker (lambda>1) the voltage falls towards 0mV.
The upstream HO2S is used by the ECM to monitor the oxygen content of the exhaust gasses leaving the engine before they reach the catalytic converter. The ECM will check the output from the HO2S to determine the combustion mixture and ensure lambda=1 is obtained. Lambda=1 is the optimum air/fuel ratio which relates to a mixture of 14.7 kg air per 1 kg of fuel (14.7:1).
The HO2S uses current regulation and outputs a linear signal dependent on the ratio of exhaust gas oxygen to ambient oxygen. The oxygen content of the exhaust gasses is measured by comparing it with ambient air drawn into the HO2S.

Downstream HO2S
Two downstream HO2S are used and are located in the each exhaust system after the starter catalytic converter. The downstream HO2S are used by the ECM to monitor the oxygen content of the exhaust gasses leaving the catalytic converter. The ECM can use this information to check (when the conditions for catalyst diagnostics have been met) for correct operation of the catalytic converter.
The ECM uses the information from the downstream HO2S to enhance the signals from the upstream HO2S.
The downstream HO2S are similar in their construction to the upstream HO2S with the exception of the output signal to the ECM. The output signal is a binary signal where the amplitude of the signal curve changes considerably when the oxygen content in the exhaust gasses changes. The oxygen content of the exhaust gasses leaving the catalytic converter are measured by comparing it with ambient air drawn into the HO2S.

Stop Lamp Switch





The stop lamp switch is attached to the brake pedal bracket, adjacent to the speed control inhibit switch. When the brake pedal is pressed, a plate on the pedal moves away from the switch plunger allowing the plunger to extend and complete the switch contacts.
The switch receives a permanent, fused battery voltage via the BJB and the CJB. The switch is connected to the ECM which provides the ground path. The ground (battery voltage signal) is used by the ECM as a switch operation signal. The ground from the switch is routed via the CJB to the ECM which allows the CJB to also determine the switch operation.
The CJB uses the completed ground when the switch is operated to activate the stop lamps.
The ECM can diagnose the operation of the stop lamp switch and the status of the switch can be read using a Land Rover approved diagnostic system.

Ambient Air Temperature (AAT) Sensor





The AAT sensor is located in the underside of the Left Hand (LH) exterior door mirror. The sensor is a Negative Temperature Co-efficient (NTC) thermistor element. The element resistance decreases as the sensor temperature increases which produces a low signal voltage. The ECM supplies the sensor with a 5V reference voltage and a ground and measures the returned signal voltage as an outside temperature.
The AAT signal is used by the ECM for a number of functions including engine cooling fan control and A/C compressor displacement control. The ECM also transmits a message on the high speed CAN bus relating to the current outside temperature for use by other control modules.
The ECM can diagnose the operation of the AAT sensor and the sensor output values can be read using a Land Rover approved diagnostic system.

Fuel Pump Driver Module (FPDM)





The FPDM is located in the LH rear corner of the luggage compartment, behind the trim panel and is secured to the LH chassis longitudinal with 2 screws.
The FPDM receives a battery supply via the fuel pump relay in the CJB. The relay is energized by the CJB when a request is received from the ECM. Two wires connect the FPDM to the fuel pump motor and a ground is via a body ground point. The ECM is connected to the FPDM on a single wire and this is used to control the pump pressure output and consequently the pump output pressure. The ECM uses signals from the MAP sensor, the fuel rail pressure/temperature sensor and the MAF/IAT sensor to determine and control the pump output.
The ECM outputs a PWM signal to the FPDM. The frequency of the signal determines the duty cycle of the FPDM which subsequently controls the pump pressure output. The frequency of the PWM signal represents half of the 'on' time of the pump. If the ECM outputs a PWM signal of 50% on time, the FPDM will operate the pump at 100% (permanently on). If the ECM outputs a PWM signal of 5%, the FPDM will operate the pump at 10% on time. The FPDM will only operate the fuel pump if it receives a PWM signal from the ECM of between 4% and 50%. If the ECM requires the pump to be stopped, the ECM transmits a PWM signal at a cycle of 75%.
If the power supply to the FPDM from the CJB or the fuel pump relay is disrupted for any reason, the fuel pump will not operate. The FPDM is monitored by the ECM for faults. Faults with the FPDM are stored in the ECM as fault codes which can be retrieved using a Land Rover approved diagnostic system.

Variable Camshaft Timing (VCT) Solenoid





The VCT solenoid is located in the LH end of the cylinder head and is secured with a bolt. The VCT solenoid is a valve which controls the oil flow to the VCT unit.
The VCT solenoid receives a fused battery supply via the main relay. The ECM provides a pulsed ground for the solenoid.
The VCT solenoid comprises an electro-magnetic valve with a spring loaded piston. Slots in the piston allows oil to be channelled to the VCT unit. The VCT unit rotates the inlet camshaft to adjust the camshaft timing as required. The direction in which the camshaft is rotated is dependent on the chamber in the VCT unit which is supplied with oil pressure from the slot in the VCT solenoid piston. For additional information, refer to Engine - 3.2L
An oil filter is located in the intake channel for the VCT solenoid to prevent contaminants affecting the function of the valve.
Operation of the valve is controlled by the ECM. The ECM provides a PWM ground for the VCT solenoid. This allows oil to be directed to different chambers in the VCT unit at variable rates, allowing the camshaft angle position to be controlled smoothly and precisely.
The ECM can diagnose the operation of the VCT solenoid and store fault related codes. The codes can be read using a Land Rover approved diagnostic system.

Camshaft Profile Switching (CPS) Solenoid - Front/Rear





Two CPS solenoids are located at each end of the cylinder head, adjacent to the inlet camshaft and are each secured with a bolt. The CPS solenoids supply oil pressure to the hydraulic tappet locking pins allowing the camshaft profile to be changed. Each solenoid controls the oil pressure supply to the hydraulic tappet locking pins on 3 cylinders. For additional information, refer to Engine - 3.2L
The CPS solenoids receive a fused battery supply via the main relay. The ECM provides a ground for the solenoid, which actuates a valve within the solenoid allowing oil pressure to adjust the camshaft profile.
The ECM can diagnose the operation of the CPS solenoids and store fault related codes. The codes can be read using a Land Rover approved diagnostic system.

Ignition Coils





Six plug top coils are used on the i6 engine and are located in recesses in the top of the cylinder head. The coils are controlled by the ECM and receive a fused, battery voltage supply via the main relay. The ECM controls the spark timing and production by switching the primary circuit of each coil to ground allowing the charge which has built up in the coil to produce a spark at the spark plug.
Each coil contains a power stage which controls the primary current and the ECM sends a signal to each coil to operate the power stage switching at the appropriate time. Each coil has a feedback wire to the ECM which allows the ECM to diagnose each individual coil and store fault related codes. The codes can be read using a Land Rover approved diagnostic system.
A suppressor is mounted on the camshaft cover adjacent to ignition coil 3 to prevent interference from the coils and/or the injectors affecting audio operation.