Electronic Engine Controls (V8 5.0L Petrol): Other Jaguar XF I

CONTROL DIAGRAM

Note. A = Hardwired; D = High speed controller area network (CAN) bus.

Control Diagram Sheet 1 Of 2

Scheme 84

Control Diagram Sheet 2 Of 2

Scheme 85

ECM ADAPTIONS

The engine control module (ECM) has the ability to adapt the input values it uses to control certain outputs. This capability maintains engine refinement and ensures the engine emissions remain within the legislated limits. The components which have adaptions associated with them are

1. The accelerator pedal position (APP) sensor
2. The heated oxygen sensors
3. The mass air flow and temperature (MAFT) sensors
4. The crankshaft position (CKP) sensor
5. Electronic throttle.

OXYGEN AND MAFT SENSORS

There are several adaptive maps associated with the fueling strategy. Within the fueling strategy the engine control module (ECM) calculates short-term adaptions and long term adaptions. The engine control module (ECM) will monitor the deterioration of the heated oxygen sensors over a period of time. It will also monitor the current correction associated with the sensors.

The engine control module (ECM) will store a fault code in circumstances where an adaption is forced to exceed its operating parameters. At the same time, the engine control module (ECM) will record the engine speed, engine load and intake air temperature.

CRANKSHAFT POSITION SENSOR

The characteristics of the signal supplied by the crankshaft position (CKP) sensor are learned by the engine control module (ECM). This enables the engine control module (ECM) to set an adaption and support the engine misfire detection function. Due to the small variation between different drive plates and different crankshaft position (CKP) sensors, the adaption must be reset if either component is renewed, or removed and refitted. It is also necessary to reset the drive plate adaption if the engine control module (ECM) is renewed or replaced. The engine control module (ECM) supports four drive plate adaptions for the crankshaft position (CKP) 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 engine control module (ECM) 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 legislated emissions limit being exceeded by a given amount. The second level is a misfire that may cause catalytic converter damage.

The engine control module (ECM) monitors the number of misfire occurrences within two engine speed ranges. If the engine control module (ECM) detects more than a predetermined number of misfire occurrences within either of these two ranges, over two consecutive journeys, it will record a fault code and details of the engine speed, engine load and engine coolant temperature. In addition, the engine control module (ECM) 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 catalytic converters. If the number of misfires exceeds a given value, the engine control module (ECM) stores catalytic converter damage fault codes, along with the engine speed, engine load and engine coolant temperature.

The signal from the crankshaft position (CKP) sensor indicates how fast the poles on the drive plate are passing the sensor tip. A sine wave is generated each time a pole passes the sensor tip. The engine control module (ECM) can detect variations in drive plate speed by monitoring the sine wave signal supplied by the crankshaft position sensor. By assessing this signal, the engine control module (ECM) can detect the presence of an engine misfire. At this time, the engine control module (ECM) will assess the amount of variation in the signal received from the crankshaft position (CKP) sensor and assign a roughness value to it. This roughness value can be viewed within the real time monitoring feature using Jaguar approved diagnostic equipment. The engine control module (ECM) will evaluate the signal against a number of factors and will decide whether to record the occurrence or ignore it. The engine control module (ECM) can assign a roughness and misfire signal for each cylinder.

The crankshaft position (CKP) sensor is an inductive sensor that allows the engine control module (ECM) to determine the angular position of the crankshaft and the engine speed.

The crankshaft position (CKP) sensor is installed in the rear left side of the sump body, in line with the engine drive plate. The sensor is secured with a single screw and sealed with an O-ring. A two pin electrical connector provides the interface with the engine harness.

The head of the crankshaft position (CKP) sensor faces a reluctor ring pressed into the outer circumference of the engine drive plate. The reluctor ring has a 60 minus 2 tooth pattern. There are 58 teeth at 6° intervals, with two teeth removed to provide a reference point with a centerline that is 21° before top dead center (BTDC) on cylinder 1 of bank A.

If the crankshaft position (CKP) sensor fails, the engine control module (ECM)

1. Uses signals from the camshaft position (CMP) sensors to determine the angular position of the crankshaft and the engine speed
2. Adopts a limp home mode where engine speed is limited to a maximum of 3000 rev/min.

With a failed crankshaft position (CKP) sensor, engine starts will require a long crank time while the engine control module (ECM) determines the angular position of the crankshaft.

CAMSHAFT POSITION SENSORS

The camshaft position (CMP) sensors are MRE (magneto resistive element) sensors that allow the engine control module (ECM) to determine the angular position of the camshafts. MRE sensors produce a digital output which allows the engine control module (ECM) to detect speeds down to zero.

The four camshaft position (CMP) sensors are installed in the front upper timing covers, one for each camshaft.

Each camshaft position (CMP) sensor is secured with a single screw and sealed with an O-ring. On each camshaft position (CMP) sensor, a three pin electrical connector provides the interface with the engine harness.

The head of each camshaft position (CMP) sensor faces a sensor wheel attached to the front of the related variable camshaft timing (VCT) unit.

If a camshaft position (CMP) sensor fails, the engine control module (ECM)

1. Defaults to base mapping for the ignition timing, with no cylinder correction
2. Disables the variable camshaft timing (VCT) system.

ENGINE COOLANT TEMPERATURE SENSORS

The engine coolant temperature (ECT) sensors are negative temperature coefficient (NTC) thermistors that allow the engine control module (ECM) to monitor the engine coolant temperature.

There are two identical engine coolant temperature (ECT) sensors installed, which are identified as ECT 1 and ECT 2. Each sensor is secured with a twist-lock and latch mechanism, and is sealed with an O-ring. A two pin electrical connector provides the interface between the sensor and the engine harness.

ECT 1

ECT 1 is installed in the heater manifold, at the rear of the right-hand (RH) cylinder head. The input from this sensor is used in calibration tables and by other systems.

ECT 2

ECT 2 is installed in the lower hose connector which attaches to the bottom of the thermostat. The input from this sensor is used for on-board diagnostic (OBD) 2 diagnostics and, in conjunction with the input from ECT 1, to confirm that the thermostat is functional.

KNOCK SENSORS

The knock sensors are piezo-ceramic sensors that allow the engine control module (ECM) to employ active knock control and prevent engine damage from pre-ignition or detonation.

Two knock sensors are installed on the inboard side of each cylinder head, one mid-way between cylinders 1 and 2, and one mid-way between cylinders 3 and 4. Each knock sensor is secured with a single screw. On each knock sensor, a two pin electrical connector provides the interface with the engine harness.

The engine control module (ECM) compares the signals from the knock sensors with mapped values stored in memory to determine when detonation occurs on individual cylinders. When detonation is detected, the engine control module (ECM) retards the ignition timing on that cylinder for a number of engine cycles, then gradually returns it to the original setting.

The engine control module (ECM) cancels closed loop control of the ignition system if the signal received from a knock sensor becomes implausible. In these circumstances the engine control module (ECM) defaults to base mapping for the ignition timing. This ensures the engine will not become damaged if low quality fuel is used. The malfunction indicator lamp (MIL) will not illuminate, although the driver may notice that the engine 'pinks' in some driving conditions and displays a drop in performance and smoothness.

The ECM calculates the default value if one sensor fails on each bank of cylinders

MANIFOLD ABSOLUTE PRESSURE SENSOR

The manifold absolute pressure (MAP) sensor allows the engine control module (ECM) to calculate the load on the engine, which is used in the calculation of fuel injection time.

The manifold absolute pressure (MAP) sensor is installed in the air inlet of the intake manifold. The sensor is secured with a single screw and sealed with an O-ring. A three pin electrical connector provides the interface with the engine harness.

If the manifold absolute pressure (MAP) sensor fails, the engine control module (ECM) adopts a default value of 1 bar (14.5 lbf/in. 2 ).

With a failed manifold absolute pressure (MAP) sensor, the engine will suffer from poor starting, rough running and poor driveability.

MASS AIR FLOW AND TEMPERATURE SENSORS

The mass air flow and temperature (MAFT) sensors allow the engine control module (ECM) to measure the mass and the temperature of the air flow into the engine. The mass air flow is measured with a hot film element in the sensor. The temperature of the air flow is measured with a negative temperature coefficient (NTC) thermistor in the sensor. The mass air flow is used to determine the fuel quantity to be injected in order to maintain the stoichiometric air/fuel mixture required for correct operation of the engine and the catalytic converters.

There are two mass air flow and temperature (MAFT) sensors installed, one in each air cleaner outlet duct. Each mass air flow and temperature (MAFT) sensor is secured with two screws and sealed with an O-ring. On each mass air flow and temperature (MAFT) sensor, a five pin electrical connector provides the interface with the engine harness.

If the hot film element signal fails the engine control module (ECM) invokes a software backup strategy to calculate the mass air flow from other inputs. Closed loop fuel control, closed loop idle speed control and evaporative emissions control are discontinued. The engine will suffer from poor starting, poor throttle response and, if the failure occurs while driving, the engine speed may dip before recovering.

If the negative temperature coefficient (NTC) thermistor signal fails the engine control module (ECM) adopts a default value of 25 °C (77 °F) for the intake air temperature.

THROTTLE POSITION SENSORS

The throttle position (TP) sensors allow the engine control module (ECM) to determine the position and angular rate of change of the throttle blade.

There are two throttle position (TP) sensors located in the electronic throttle. See below for details of the electronic throttle.

If a throttle position (TP) sensor fails, the engine control module (ECM)

1. Adopts a limp home mode where engine speed is limited to a maximum of approximately 2000 rev/min
2. Discontinues evaporative emissions control
3. Discontinues closed loop control of engine idle speed.

With a failed throttle position (TP) sensor, the engine will suffer from poor running and throttle response.

HEATED OXYGEN SENSORS

The heated oxygen sensors allow the engine control module (ECM) to measure the oxygen content of the exhaust gases, for closed loop control of the fuel: air mixture and for catalytic converter monitoring.

An upstream heated oxygen sensor is installed in the outlet of each exhaust manifold, which enables independent control of the fuel: air mixture for each cylinder bank. A downstream heated oxygen sensor is installed in each catalytic converter, which enables the performance of the catalytic converters to be monitored.

Oxygen sensors need 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 pulse width modulation (PWM) signal from the engine control module (ECM). The heater elements are operated immediately after each engine start and during low load conditions when the temperature of the exhaust gases is insufficient to maintain the required sensor temperature. The pulse width modulation (PWM) duty cycle is carefully controlled to prevent thermal shock to cold sensors. A non-functioning heater delays the sensor's readiness for closed loop control and increases emissions.

The upstream heated oxygen sensors produce a constant voltage, with a variable current that is proportional to the lambda ratio. The downstream heated oxygen sensors produce an output voltage dependent on the ratio of the exhaust gas oxygen to the ambient oxygen.

The heated oxygen 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 engine control module (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.

If a heated oxygen sensor fails

1. The engine control module (ECM) defaults to open loop fueling for the related cylinder bank
2. The CO (carbon monoxide) and emissions content of the exhaust gases increases
3. The exhaust smells of rotten eggs (hydrogen sulphide).

With a failed heated oxygen sensor, the engine will suffer from unstable operation and reduced performance.

ACCELERATOR PEDAL POSITION SENSORS

The accelerator pedal position (APP) sensor allows the engine control module (ECM) to determine the driver requests for vehicle speed, acceleration and deceleration. The engine control module (ECM) uses this information to determine the setting of the electronic throttle.

The accelerator pedal position (APP) sensor is installed on the pedal box and secured with three screws. A six pin electrical connector provides the interface with the vehicle harness. The accelerator pedal is connected to a spindle on the right-hand (RH) side of the accelerator pedal position (APP) sensor.

The accelerator pedal position (APP) sensor is a twin track potentiometer. Each track receives an independent power supply from the engine control module (ECM) and returns an independent analog signal to the engine control module (ECM). Both signals contain the same positional information, but the signal from track 2 is half the voltage of the signal from track 1 at all positions.

If both signals have a fault, the engine control module (ECM) adopts a limp home mode, which limits the engine speed to 2000 rev/min maximum.

The engine control module (ECM) constantly checks the range and plausibility of the two signals and stores a fault code if it detects a fault.

Scheme 86

The AAT (ambient air temperature) sensor is a negative temperature coefficient (NTC) thermistor that allows the engine control module (ECM) to monitor the temperature of the air around the vehicle. The engine control module (ECM) uses the AAT input for a number of functions, including engine cooling fan control. The engine control module (ECM) also transmits the ambient temperature on the high speed controller area network (CAN) bus for use by other control modules.

The AAT sensor is installed in the left-hand (LH) exterior mirror, with the bulb of the sensor positioned over a hole in the bottom of the mirror casing.

The engine control module (ECM) supplies the sensor with a 5 V reference voltage and a ground, and translates the return signal voltage into a temperature.

If there is a fault with the AAT sensor, the engine control module (ECM) calculates the AAT from the temperature inputs of the mass air flow and temperature (MAFT) sensors. If the AAT sensor and the temperature inputs of the mass air flow and temperature (MAFT) sensors are all faulty, the engine control module (ECM) adopts a default ambient temperature of 20°C (68°F).

ELECTRONIC THROTTLE

The engine control module (ECM) uses the electronic throttle to regulate engine torque.

The electronic throttle is installed between the T piece duct, of the intake air distribution and filtering system, and the inlet of the supercharger (SC). For additional information, refer to 303-12E Intake Air Distribution and Filtering.

The throttle plate is operated by an electric DC (direct current) motor integrated into the throttle body. The engine control module (ECM) uses a pulse width modulation (PWM) signal to control the DC motor. The engine control module (ECM) compares the accelerator pedal position (APP) sensor inputs against an electronic map to determine the required position of the throttle plate. The engine control module (ECM) and electronic throttle are also required to

1. Monitor requests for cruise control operation
2. Automatically operate the electronic throttle for accurate cruise control
3. Perform all dynamic stability control engine interventions
4. Monitor and carry out maximum engine speed and road speed cut outs
5. Provide different engine maps for the ride and handling optimization system.

A software strategy within the engine control module (ECM) calibrates the position of the throttle plate at the beginning of each ignition cycle. When the ignition is turned on, the engine control module (ECM) performs a self test and calibration routine by fully closing the throttle plate and then opening it again. This tests the default position springs and allows the engine control module (ECM) to learn the position of the closed hard stop. Subsequently the engine control module (ECM) keeps the throttle plate a minimum of 0.5 degree from the closed hard stop.

MAIN RELAY

The main relay is used to initiate the power up and power down routines within the engine control module (ECM). The main relay is installed in the engine junction box (EJB).

When the ignition is turned on, battery voltage is applied to the ignition sense input. The engine control module (ECM) then starts its power up routines and energizes the main relay.

When the ignition is turned off, the engine control module (ECM) maintains its powered up state while it conducts the power down routines (up to 20 minutes in extreme cases, when cooling fans are required) and on completion will turn off the main relay.

HEATED OXYGEN SENSOR (HO2S) LH

Special Tool(s)

310-121 Wrench, H02S

Scheme 87

HEATED OXYGEN SENSOR (HO2S) RH

Special Tool(s)

310-121 Wrench, H02S