Land Rover Bosch 5 2 1 Engine Management Systems Rover Manual

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 147 The ECM will also store details of the engine speed, engine load and air temperature in its 
memory. This information is stored to aid diagnosis of the fault
Coolant Sensor Operational Values  
Knock sensors
There are two knock sensors on the V-8 engine, both located 
directly on the cylinder block, one on each side. The knock 
sensors produce a voltage signal in proportion to the amount of 
mechanical vibration generated at each ignition point. Each 
sensor monitors the four cylinders in one bank.
The knock sensors incorporate a piezoceramic crystal. This 
crystal produces a voltage whenever an outside force tries to 
deflect it, (i.e. exerts a mechanical load onto it). When the 
engine is running, the compression waves in the material of the 
cylinder block, caused by the violent combustion of the fuel/air 
mixture within the cylinders, deflect the crystal. As described 
above, these forces acting on the crystals cause them to produce an output voltage signal. 
These signals are supplied to the ECM and compared with sample ‘mapped’ signals stored 
within its memory. From this, the ECM can identify when the ignition is too far advanced and 
causing pre-ignition problems.  
Care must be taken at all times to avoid damaging the knock sensors, but particularly during 
removal and installation procedures. The recommendations regarding to torque and surface 
preparation must be adhered to. The torque applied to the sensor and the quality of the surface 
preparation both have an influence over the transfer of mechanical noise from the cylinder block 
to the crystal.  
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
148 The ECM uses the signals supplied by the knock sensors in conjunction with the camshaft 
sensor signal, to determine the optimum ignition point for each cylinder. The ignition point is set 
according to pre-programmed ignition maps stored within the ECM. In this case, the ECM is 
programmed to use ignition maps for 95 RON premium specification fuel. It will also function on 
91 RON regular specification fuel but without adaptations. If the only fuel available is of poor 
quality, or the customer switches to a lower grade of fuel after using a high grade for a period of 
time, the engine may suffer slight pre-ignition for a short period. This amount of pre-ignition will 
not damage the engine. This situation will be evident while the ECM learns and then modifies its 
internal mapping to compensate for the variation in fuel quality. This feature is called 
‘adaptations’. The ECM has the capability of adapting its fuel and ignition control outputs in 
response to several sensor inputs.
Unlike previous Land Rover engine management systems, the Bosch 5.2.1 system is capable 
of advancing the ignition timing for improved power and economy, as well as retarding it.
The ECM will cancel ‘closed loop’ control of the ignition system if the signal received from either 
knock sensor becomes implausible, or the signal from the camshaft sensor is corrupted at any 
time. In these circumstances, the ECM will default to a safe ignition map. This measure ensures 
the engine will not become damaged if low quality fuel is used. The MIL lamp will not illuminate 
at this time (in any market), although the driver may notice that the engine ‘knocks’ in some 
driving conditions and displays a slight drop in performance and smoothness.  
When a knock sensor fault is stored, the ECM will also store details of the engine speed, engine 
load and the coolant temperature.
Mass Air Flow and Intake Air Temperature sensor
The mass air flow (MAF) sensor is located in the air intake 
ducting, between the air filter housing and the plenum 
chamber. The MAF sensor returns a signal to the ECM to 
indicate how much air is entering the engine. The amount of air 
entering the engine is calculated from two functions:
1  The sensor incorporates a hot film element. This film is 
heated by the circuitry in the MAF sensor. A proportion of 
the air flowing into the engine flows past the film and acts 
to cool it. The greater the air flow, the greater the cooling 
effect. The output voltage varies in accordance with the 
amount of electrical power being consumed by the mass 
air flow meter to keep the film at a predetermined temperature.
2  The MAF sensor also incorporates an intake air temperature (IAT) sensor. This sensor is an 
NTC type of sensor. It informs the ECM of the temperature of the air entering the engine. 
The temperature of the air entering the engine will affect its density. The density of the air 
entering the engine will affect its ability to support combustion. The signal supplied by the 
temperature sensor is used to calculate the cooling effect on the hot film from a given mass 
of air, along with several other fuelling calculations. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 149 The MAF sensor is sensitive to sudden shocks and changes in its orientation. It should, 
therefore, be handled carefully. It is also important that the intake ducting between the air filter 
housing and the engine plenum chamber is not altered in diameter or modified in any way. The 
air mass flow meter contains electronic circuitry, so never attempt to supply it directly from the 
battery. The terminals have a silver coating to provide a superior quality of connection over 
many years. If, at any time, a probe is used to measure the output directly from the sensor, then 
care must be taken to ensure this coating is not damaged.
If the MAF sensor signal fails then the ECM will adopt a default strategy. This strategy will cause 
the ECM to assume that a certain quantity of air is entering the engine. The exact quantity will 
be based upon the signals received relating to throttle position, engine speed and air 
temperature. The following engine symptoms will be noticeable:
•  The MIL lamp will be illuminated after the fault has been ‘validated’
•  The engine speed might ‘dip’ before the default strategy enables continued running
•  The engine may be difficult to start and prone to stalling
•  The overall performance of the engine will be adversely affected (throttle response in partic-
ular)
•  Exhaust emissions will be out of tolerance, because the air/fuel ratio value is now assumed, 
not calculated; no closed loop fuelling
•  Idle speed control disabled, leading to rough idle and possible engine stall
At the time of failure, the ECM will store details of the engine speed, coolant temperature and 
throttle angle.
If the signal from the air temperature sensor fails, the ECM will assume a default value of 112°F 
(45°C). This default value is then used within all the calculations involving intake air 
temperature. The effect on the vehicle of a failed air temperature signal will not be so noticeable 
to the driver, who may notice a reduction in engine performance when operating the vehicle at 
high altitudes or in hot ambient temperatures. The occurrence of this fault will also disable 
fuelling adaptations and the catalyst monitoring function of the ECM. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
150 The ECM will store details of the engine speed, engine load and battery voltage when this fault 
is first detected.
Oxygen sensors
There are four Oxygen sensors used on the V-8 Discovery Series II.  Two of the sensors are 
located in each downpipe. 
11- “Downstream” Sensor tip     12- “Upstream” Sensor tip
One sensor is used upstream of the catalyst, i.e. between the catalyst and the engine, and one 
is used immediately downstream of the catalyst. The two sensors used upstream of the catalyst 
are referred to as ’pre-catalyst’ sensors (12), while the two sensors used downstream  are 
referred to as ’post-catalyst’ sensors (11). It should be noted that the ‘pre-catalyst’ Oxygen 
sensors are not interchangeable with the ‘post’ catalyst Oxygen sensors.  The pre and post 
sensors can be identified by the shape of the vents on their protective metal tip shell., as shown 
below. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 151 The Oxygen sensors are very sensitive devices. They must be handled carefully at all times. 
Failure to handle correctly will result in a very short service life, or non-operation.
Oxygen sensors are pre-coated with an anti-seize compound prior to installation. Care should 
be taken to avoid getting this compound on the sensor tip. 
If the sensor needs to be removed and reinstalled, a small amount of anti-seize compound 
should be applied (see workshop manual for details). 
The Oxygen  sensors use ‘Zirconium technology’. The sensors feature a Galvanic cell (6), 
which is surrounded by a gas permeable ceramic material (9) enclosed by a protective metal 
shell (10). This allows exhaust gas to come into contact with one side of the sensor. The other 
side of the sensor is exposed to the atmosphere. Due to its construction, the sensor produces a 
voltage. The precise value of the voltage produced is dependent upon the ratio of Oxygen in the 
atmosphere compared to the Oxygen in the exhaust gas. The voltage produced for an exhaust 
gas with Lambda 1 (i.e. stoichiometric air, fuel ratio of 14.7:1) is 0.45 - 0.5 volts (450 – 500 mv). 
The voltage will fall in value to approximately 0.1 volts (900 mv), or Lambda 0.8, when the 
Oxygen in the exhaust gas rises (lean mixture - too much air in relation to fuel). The voltage will 
rise in value to approximately 0.9 volts when the Oxygen level in the exhaust gas falls to 
approximately Lambda 1.2 (rich mixture - too much fuel in relation to air).   
The voltage from the Oxygen sensor is communicated to the ECM via the Oxygen sensor signal 
wires (1, 5). The ECM monitors the effect of altering the injector pulse widths uses the 
information supplied by the Oxygen sensors. Injector pulse width is the length of time the 
injector is energized, which determines how much fuel is injected. The response time is such 
that under certain driving conditions, the ECM can assess individual cylinder contributions to 
the total exhaust emissions. This enables the ECM to adapt the fuelling strategy on a cylinder 
by cylinder basis, i.e. inject the precise amount of fuel required by each individual cylinder at 
any given time.
The ECM continuously checks the signals supplied by the Oxygen sensors for plausibility. If it 
detects an implausible signal, then it will store a relevant fault code. On the second concurrent 
‘journey’ that a fault is recognized, the ECM will illuminate the MIL lamp and store details of 
engine speed, engine load and the Oxygen sensor voltage. The ECM requires the Oxygen 
sensor signals to set most of its adaptations. Failure of an Oxygen sensor will result in most of 
these adaptations resetting to their default values. This, in turn, will result in the engine losing its 
‘finesse’. The engine may exhibit poor idle characteristics and emit a strong smell of rotten eggs 
from the exhaust (H2S).
The efficiency of the Oxygen sensors slowly deteriorates over many kilometers/miles (unless 
contamination such as excessive oil or lead has occurred causing sudden damage/ failure). The 
ECM is able to detect this steady deterioration using the feedback signals. When a signal from 
a sensor deteriorates beyond a predetermined threshold, the ECM will illuminate the MIL lamp 
and store a fault code. At the same time, the ECM will capture details of the engine speed, 
engine load and battery voltage. The sensor response time will normally deteriorate over its life, 
however the engine management system monitors performance, and will illuminate the MIL 
when a sensor requires replacement. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
152 The ECM also monitors the efficiency of the catalysts. The ECM uses the signal received from 
the two post-catalyst Oxygen sensors to do this. The state of each catalyst is assessed in line 
with its ability to ‘hold’ Oxygen. In a serviceable unit the ‘excess’ Oxygen in the exhaust gas is 
held on the surface of the precious metal coating of the ceramic blocks within the catalyst. This 
Oxygen is used to convert the harmful elements produced by incomplete combustion 
(particularly during acceleration and conditions where the engine requires a rich air/fuel ratio) 
into Carbon Dioxide, Nitrogen and water. By comparing the signals received from the pre-
catalyst sensors with those received from the post-catalyst sensors, the ECM can calculate how 
much Oxygen is retained by each catalyst and can, therefore, determine their condition. If the 
ECM determines that one or both catalysts require replacement, then it will illuminate the MIL 
(after validating the fault) and store the relevant fault code. At the same time, the ECM will 
record details of the engine speed, engine load and air temperature.
Zirconium Oxygen sensors need high operating temperatures to work effectively. To ensure a 
suitable operating temperature is reached as soon as possible, each sensor incorporates a 
heating element inside the ceramic tip. This element heats the Oxygen sensor to a temperature 
greater than 670°F (350°C). The heating rate (the speed at which the temperature rises) is 
carefully controlled by the ECM to prevent thermal shock to the ceramic material. By way of a 
PWM voltage supply to the heater elements, the ECM controls.
The rate at which the element temperature is increased. The sensors are heated during engine 
warm-up and again after a period of engine idle.
The ECM monitors the state of the heating elements by calculating the amount of current 
supplied to each sensor during operation. If the ECM identifies that the resistance of either 
heating element is too high or too low, it will store a fault code, the engine speed, coolant 
temperature and the battery voltage. When the fault is logged twice on consecutive ‘journeys’, 
the MIL lamp will illuminate.
Immobilisation signal
The BCU sends a coded signal to the ECM before it activates the starter motor. If the ECM 
accepts the immobilization signal (i.e. the code is correct), the engine will be permitted to start 
and will continue to run normally. If the immobilization signal is corrupted (i.e. not sent, or 
incorrect), then the ECM will allow the engine to start, but will then stop it immediately. 
If the BCU is replaced during the service life of the vehicle, the immobilization code will need to 
be relearned. If an attempt to start the engine is made with a new ECM installed on the vehicle 
(an ECM not yet programmed with any immobilization code), the ECM will not allow the engine 
to start and will store a fault code. This fault code must be cleared and the immobilization code 
learned before the ECM will allow the engine to run.
The immobilization code must also be relearned in cases where an ECM from one vehicle is 
used on another. 
If the ECM detects an incorrect immobilization code it will store a fault code. Simultaneously, the 
ECM will record the engine speed, battery voltage and the number of occurrences (the number 
of times the incorrect code has been detected).  
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 153 Fuel level signal
This signal is supplied to the ECM by the instrument pack. It is used to alter the fault code 
strategy adopted by the ECM when a misfire is detected (see misfire detection) or if the ECM 
detects that the Oxygen signal is unexpectedly recording a weak air/fuel ratio. It will not stop a 
fault being logged but will modify the fault code to indicate the likely cause of the misfire.
Vehicle speed sensor signal
The ECM uses this signal within its calculations for idle control. The ECM also forwards the 
vehicle speed signal to the automatic gearbox TCM via the CAN bus. The vehicle speed signal 
is produced by the SLABS ECU. The signal is calculated from the road speed signals of all four 
wheel speed sensors.
Rough road signal
This signal is also produced by the SLABS ECU. It is derived from the variations between each 
signal received from the four wheel speed sensors (see section on ABS for full description).
The ECM alters its misfire detection strategy whenever a rough road signal is received. The 
ECM will not store details of a misfire fault at this time (see misfire detection strategy).
Automatic temperature control system request
A signal is supplied to the ECM whenever the ATC system requires the compressor clutch and/
or condenser fans to function. The ECM integrates the control of these components with the 
engine management system. This ensures effective engine preparation for any sudden 
increase in the engine load.
The ECM will turn off the ATC compressor clutch if the engine coolant temperature exceeds 
255°F (124°C).  The ECM will turn on the condenser fans if the engine coolant temperature 
exceeds 212°F (100°C). See section on ATC for more details on the exact operation of the 
compressor clutch and condenser fans.
The ECM will store engine speed, battery voltage and engine load details whenever it detects a 
fault originating from the ATC circuit. It will store engine speed, intake air temperature and 
details of the battery voltage if the fault relates to the compressor clutch or condenser fan 
operation.
Automatic gearbox information
Information sent to and from the automatic gearbox TCM is transmitted on the CAN bus. Full 
details of this information are in the section on automatic gearbox.
The ECM requires information on gear position to calculate the likely engine load during 
acceleration and deceleration conditions. The ECM also disables the misfire detection function 
whenever low range is selected. Information regarding range selection is supplied by the TCU.
There are several possible fault codes associated with the CAN bus and the validity of 
information sent to and from the ECM from the TCU. In most cases, the ECM will store engine 
speed, engine coolant temperature and details of the battery voltage at the time when the fault 
is detected.  
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
154 The automatic transmission TCM is able to request the illumination of the MIL lamp if it detects 
a fault within its systems that might lead to the vehicle emitting excessive levels of pollutants. It 
is good practice to check both ECM and the automatic gearbox TCM for faults when the MIL 
lamp is illuminated, or a MIL event is logged in the ECM.
Fuel tank pressure sensor
The fuel tank pressure sender is located in the fuel tank. This unit supplies a signal to the ECM 
related to the amount of fuel vapor pressure within the fuel tank. It is used as a feedback device 
within the ECM’s evaporative emission control (EVAP) leak test. This test is detailed later in the 
section.
If a fault is present, the ECM will store a relevant fault code and the engine speed value, battery 
voltage and details of the engine coolant temperature. If the fault happen on the next ‘journey’, 
the ECM will illuminate the MIL lamp. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 155 System Outputs
The ECM receives and processes the input information previously described and modifies the 
fuelling and the ignition points for each cylinder accordingly. The ECM will also supply output 
information to other vehicle system ECUs.
The ECM drives the following components:
•  Fuel injectors
•  Ignition coils
•  Idle speed actuator
•  Main relay and fuel pump relay
•  Purge valve
The ECM provides other systems with information regarding the -
•  Engine speed
•  Driver demand
•  Grant signals ATC
•  Grant signals Automatic Transmission 
Ignition coils
The V-8 gasoline engine in Discovery Series II uses two twin-ignition coils (total of four coils). 
The two coils are located behind the plenum chamber at the rear of the engine (see figure 57). 
Each coil contains two primary windings and two secondary windings. There is a three-pin 
connector on each coil. Pin two connects both primary windings to an ignition supply. There is 
one suppression capacitor connected to each supply. This helps eliminate the effect of the 
magnetic radiation created by the sudden demands for power as each coil recharges.
The system employs waste spark technology to produce a powerful and precise spark. The 
cylinders are paired according to the table below.
The ECM provides a path to ground whenever a spark 
is required. To ensure a sustained magnetic field 
collapse, the ECM carefully controls the rate of 
discharge from each coil at this time. This control also 
limits the amount of heat created during this process 
and reduces the total power consumed by each coil. 
Any faults detected within the primary and HT circuits 
will result in the ECM storing an appropriate misfire 
fault, but not a fault directly related to the spark 
creation and delivery.
Coil Set Coil 1 Coil 2 Coil 3 Coil 4
Cylinders 1 & 6 7 & 4 5 & 8 3 & 2 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
156 Fuel injectors
There are eight injectors (one per cylinder) used on the V-8 
gasoline engine. The ECM controls the injectors directly, 
and individually. It opens an injector by providing a path to 
ground for a voltage supplied by a common fuse. The 
injectors are fed fuel under pressure from a common fuel 
rail. A fuel pressure relief valve, incorporated into the lift 
pump assembly located inside the fuel tank, controls the 
pressure in the fuel rail. In this case, the pressure is 
controlled to a fixed value of 51 psi (3.5 Bar). As indicated, 
the fuel pressure is fixed and the relief valve provides no 
compensation for increases or decreases in manifold 
vacuum. The ECM alters injector duration to accommodate 
such changes.
Connecting an appropriate gauge to the Schrader valve on the fuel rail provides a method of 
checking the fuel pressure. The valve is located to the rear of injector no. 7.  Considerable care 
must be taken whenever making this connection.
Each injector is sealed with two ‘O’ rings. These ‘O’ rings should be renewed whenever an 
injector is reinstalled on an engine. A small amount of engine oil can be applied to the ‘O’ rings 
to aid installation. No other form of lubrication should be used.
Measuring the electrical resistance of the injectors internal coil enables an assessment to be 
made of the serviceability of an injector. An injector in a serviceable condition should possess a 
resistance of 14.5 ohms at 68°F (20°C) with a tolerance of ± 0.7 ohms.
The ECM can detect electrical inconsistencies within each injector. It can also detect, via 
feedback from the Oxygen sensors, mechanical faults such as blockage or leakage. The ECM 
will store a relevant fault code in these circumstances. The ECM will also store the engine 
speed, engine load and details of one of the following: battery voltage, engine coolant 
temperature or intake air temperature. The precise details stored depend on the exact nature of 
the fault detected.
TestBook will also display data regarding injector operation via its live readings. Care must be 
taken when analyzing this data, as the precise timings will vary considerably. Individual timings 
will be affected by any current engine load.