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 157 Idle speed actuator
The idle speed control actuator is located behind the throttle body on the intake manifold. It is 
connected to the intake manifold by two hoses. One hose connects upstream and the other 
connects downstream of the throttle valve. Therefore, the idle speed actuator effect provides an 
air bypass for the throttle valve.
The ECM controls the engine idle speed via the idle speed actuator. It does this by allowing a 
measured quantity of air into the engine when the throttle valve is closed. The idle speed 
actuator comprises a rotary valve and two electrical coil windings. The ECM alters the position 
of the idle speed actuator and, therefore, the amount of air bypassing the closed throttle valve 
by providing a PWM voltage to the two opposing coils inside the actuator. These coils control 
the position of the rotary valve by producing opposing magnetic fields. When the ECM identifies 
a need for a higher idle speed it enables a greater quantity of air to bypass the throttle valve. It 
does this by altering the PWM voltage supplied to both coils. This provides an imbalance in 
magnetic fields inside the actuator and, in turn, alters the amount of air bypassing the throttle 
valve. 
The ECM controls the position of the rotary valve within the idle speed actuator to maintain a 
stable idle speed in all conditions. It will alter the position to obtain a pre-set target speed. The 
precise pre-set idle speed will vary according to the operating conditions of the engine  and the 
transmission gear that is selected. These pre-set speeds are detailed in the table below.
Condition Air conditioning
statusTarget idle speed (rpm)
high rangeTarget idle speed (rpm)
low range
First 20 seconds after a cold start N/A 1200 1200
Low battery voltage detected N/A 850 850
Drive selected On 740 580
Park/ neutral selected On 740 580
Drive selected Off 660 580
Park/ neutral selected Off 660 580 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
158 For 20 seconds immediately following cold start, the idle speed will be raised to 1200 rpm. At 
the same time the ECM will retard the ignition timing. These actions ensure the engine and the 
catalysts reach their operating temperatures as quickly as possible.
The ECM can identify faults with the circuitry used to control the position of the idle speed 
actuator. In circumstances where it detects a fault with one coil it will de-energise the other coil. 
This action prevents the idle speed control valve being driven to a fully open or fully closed 
position. The idle speed control actuator contains two permanent magnets inside the body. 
These magnets will determine the position of the valve at this time. In this position the engine 
will idle at approximately 1200 rpm. This state should not be confused with the target idle speed 
initiated by the ECM for the first 20 seconds immediately following cold engine start.
The ECM will store fault codes relating to the electrical properties of the idle speed actuator and 
to associated failures, such as poor engine response to movement of the rotary valve. The 
associated data stored will depend upon which fault is detected, such as battery voltage, engine 
coolant temperature and throttle angle for faults related to the circuitry; or engine speed, engine 
coolant temperature and intake air temperature for ‘poor response’ fault codes.
If ECM control of the idle speed actuator is suspended, (i.e. fault stored), then the driver may 
notice the following symptoms relating to engine performance:
•  The engine will exhibit poor idle stability
•  The engine will exhibit a high idle speed
•  The engine will be prone to stalling
•  The engine will be difficult to start    
Main relay and fuel pump relay
The ECM controls the main relay and the fuel pump relay. They are both located in the under-
hood fuse box.
The ECM energizes the fuel pump relay when the ignition is first turned to position II. It also 
energises it during engine cranking and when the engine is running. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 159 The ECM controls its own power supply, via the main relay. When the ignition is turned to 
position II, the ECM provides a ground to the relay coil winding. This, in turn, connects the main 
power feed to the ECM. The ECM controls the main relay and therefore its own power, so that 
when the ignition is turned off it can follow the previously described power-down sequence, 
during which it records values from various sensors and writes adaptations into its memory, etc. 
The last action the ECM carries out before completing its power-down sequence is to turn off 
the main relay. This will occur approximately 15 seconds after the ignition has been switched 
off, as long as the coolant temperature is not rising.
The ECM monitors the state of the wiring to the coil winding within the fuel pump relay. The 
ECM will store relevant fault codes if the ECM detects a problem. The ECM is not able to 
assess the state of the fuel pump circuit because it is isolated by the function of the relay. 
However, if the fuel pump circuit fails, or the pump fails to deliver sufficient fuel (while the fuel 
level is above its minimum), the ECM will store adaptive faults as it tries to increase the air/fuel 
ratio by increasing the duration (pulse width) of the injectors.
Failure of the main relay will result in engine non-start. The engine will cease to operate if the 
main relay fails while the engine is running.
Failure of the fuel pump relay will result in engine non-start. If the fuel pump fails while the 
engine is running, the symptoms will be engine hesitation and engine misfire. These symptoms 
will worsen progressively until the engine stops. The ECM will store several fault codes under 
this condition.
Purge valve
The purge valve is located on the right hand side of the engine (when viewed from the front of 
the vehicle) forms part of the evaporative emission control system (EVAP) and is situated in the 
line between the charcoal canister and the manifold. The purge valve controls the amount of air/
fuel vapor drawn from the canister into the engine. The other components incorporated into the 
EVAP system are:
•  The charcoal canister, which is located on the right hand inner chassis rail by the hand  
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
160brake drum
•  The fuel tank pressure sensor, located in the fuel sender unit
•  The intake manifold
The ECM controls the amount of vapor drawn from the charcoal canister by controlling the 
length of time the purge valve is open. It controls the length of time it is open by supplying the 
purge valve with a PWM voltage. Control is used to maintain the required level of emissions, as 
a hydrocarbon vapor level of 1% can affect the air/fuel ratio by as much as 20%.
The ECM can diagnose faults with the purge valve and the rest of the EVAP system. The ECM 
will store the relative fault codes, along with details of the engine speed, battery voltage and air 
temperature. The driver may notice the following effects in circumstances where the EVAP 
system has failed:
•  The engine may stall periodically when returning to idle
•  The engine may suffer from poor idle quality
OTHER ECM OUTPUTS
Engine speed
The engine speed signal is supplied from the ECM to the automatic gearbox TCM via the CAN 
bus. All other systems requiring the engine speed input receive a frequency dependent square 
wave supplied by the ECM.
Driver demand
The ECM receives and processes the signal supplied by the throttle position sensor. It then 
digitises this information, which enables it to supply a driver demand signal, via the CAN bus, to 
the automatic gearbox TCM or, by a PWM signal, to any other system requiring this information.
ATC grant signal
The ECM supplies a signal to the ATC Compressor relay to activate the compressor.
Torque reduction grant signal
The ECM also informs the automatic gearbox TCM if its torque reduction request has been 
granted. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 161 ECM Adaptations
The ECM, as previously mentioned, 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 idle speed control (ISC) valve 
•  The throttle position sensor (TPS)
•  The Heated Oxygen sensors (HO2S)
•  The airflow sensor (MAF)
•  The crankshaft sensor (CKP)
Idle speed control valve 
Over a period of time, the ECM adapts the position it sets the idle speed control valve. The 
adaptations are made relative to engine coolant temperature and engine load. When a new idle 
speed control valve or a replacement ECM is used, this adaptation should be reset. 
Subsequently, the ECM will make further adaptations to suit the particular characteristics of the 
new or replacement components. Failure to reset the original adaptation may result in a 
prolonged period of poor idling. During this time the ECM slowly adapts the original, ‘incorrect’ 
value stored in its memory.
TestBook will display the adaptation currently being applied against the model programmed into 
its memory. This can be used to indicate the possible cause of problems relating to the amount 
of air entering the engine, such as air blockages or air leaks within the induction system.
Throttle position sensor
The ECM ‘learns’ the closed position of the throttle position sensor. The closed voltage value 
supplied by the sensor is stored by the ECM and can be read using TestBook (see TPS sensor 
for information regarding the likely readings and signal tolerance band).  If the sensor is 
replaced, the new closed throttle position will be learned by the ECM during the IMF cycle for 
the TPS.
The signal from the TPS sensor is used in conjunction with the air mass flow meter to calculate 
the altitude adaptations. This adaptation affects the amount of fuel entering the engine and the 
ignition timing. Details of the value of this adaptation are supplied to the automatic gearbox 
TCM. Using this information, it will adapt its gear change control maps. The altitude adaptation 
is continuously changing and indicates current driving conditions. Details of the altitude 
adaptation are stored within the ECM’s memory when the ignition is switched off. This enables 
the ECM to provide correct fuelling on the next engine start.
Oxygen sensors & air flow meter
There are several adaptive maps associated with the fuelling strategy. Within the fuelling 
strategy the ECM calculates short-term adaptations and long term adaptations. The ECM will 
monitor the deterioration of the Oxygen sensors over a period of time. It will also monitor the 
current correction associated with the sensors.  
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
162 The ECM will store a fault code in circumstances where an adaptation is forced to exceed its 
operating parameters. At the same time, the 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 sensor are learned by the 
ECM. This enables the ECM to set an adaptation and support the engine misfire detection 
function. Due to the small variation between different flywheels and different crankshaft 
sensors, the adaptation must be reset if either component is renewed, or removed and 
replaced. It is also necessary to reset the flywheel adaptation if the ECM is renewed or 
replaced.
The ECM supports four flywheel adaptations for the crankshaft position sensor. Each adaptation 
relates to a specific engine speed range. The engine speed ranges are detailed in the table 
below. 
To set the flywheel adaptations, follow the procedure detailed below. This procedure should be 
carried out in an appropriate area off the public highway. TestBook must be connected 
throughout this procedure. The adaptive speed settings must be read from TestBook while the 
vehicle is moving at speed.
1  Use TestBook to clear any adaptations currently set.
2  With the engine warm >187°F (86°C) select 2nd gear high range
3  Accelerate the vehicle until the engine speed reaches the rpm limiter
4  Release the throttle and allow the vehicle to decelerate until the engine idle speed is 
reached
5  Check that one of the speed range adaptations has been set (read this from TestBook)
6  Repeat the above procedure until all four adaptations are set
When all four adaptations have been set, check that the ECM has not recorded any misfire 
detection faults. If it has, then clear the memory of the fault codes.
It may not be possible to reset adaptation number 4 if the ECM has already been programmed 
with a value. Due to the nature of the procedure and the self learn capacity of the ECM, if 
adaptation number 4 does not reset, it is permissible to leave this adaptation and let the ECM 
learn it.  
Engine speed range Adaptation
1800 – 3000 1.00
3001 – 3800 2.00
3801 – 4600 3.00
4601 - 5400 4.00 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 163 Misfire detection
Legislation requires that the 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 vehicle emissions exceeding 1.5 times the allowable levels for this engine. The second 
level is a misfire that may cause catalyst damage.
The ECM monitors the number of misfire occurrences within two engine speed ranges. If the 
ECM detects more than a predetermined number of misfire occurrences within either of these 
two ranges, over two consecutive ‘journeys’, the ECM will illuminate the MIL. The ECM will also 
record details of the engine speed, engine load and engine coolant temperature. In addition, the 
ECM monitors the number of misfire occurrences that happen in a ‘window’ of 200 engine 
revolutions. The misfire occurrences are assigned a ‘weighting’ of the likely impact to the 
catalysts. If the number of misfires exceeds a certain value, the ECM stores catalyst-damaging 
fault codes, along with the engine rpm, engine load and engine coolant temperature. It will also 
flash the MIL lamp  until the misfires no longer exceed the predetermined number. After the 
flashing stops, the ECM will continue to illuminate the MIL lamp until the fault is rectified. 
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 can detect variations in flywheel speed by monitoring the sine wave signal supplied by the 
crankshaft position sensor.
By assessing this signal, the ECM can detect the presence of an engine misfire. At this time, the 
ECM 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 TestBook. The ECM will evaluate the signal against a 
number of factors and will decide whether to count the occurrence or ignore it. The ECM can 
assign a roughness and misfire signal for each cylinder, (i.e. identify which cylinder is misfiring). 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
164 TestBook Diagnostics
The ECM will, as explained earlier, store fault codes and environmental data. The ECM also 
records additional data in connection with each fault. The additional data recorded is as follows:
1  The number of occurrences
2  If the fault is currently present
3  If the fault is historic, the number of ‘journeys’ that have elapsed since the fault last 
occurred.
4  The ‘current time’ stored when the fault occurred. (The time is incremented in hours, hour 0 
being the first time the ECM is powered-up, hour 1 being 60 minutes of ignition ‘on’ time, 
etc.)
This information is displayed for each fault, along with an explanation of the fault code and the 
stored environmental data. All the above information is stored and displayed to assist with 
effective fault diagnosis and repair.
TestBook can also read real time data from each sensor, the adaptive values currently being 
employed and the current engine fuelling, ignition and idle settings. The live readings are 
displayed first as a page of readings. To gain more detail press and highlight the reading for 
which you require more information. 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 165 Connector Pinouts
Bosch 5.2.1
Connector 1
C0634 (9-way, Black)
PIN Wire
ColorDescription Voltage Reading
1 W Ignition sense (position II) 12 V
2-
3-
4 B Chassis Earth 0V
5 B Fuel Injectors Earth 0V
6 B Power stage Earth 0V
7 PY Permanent Battery supply 12 V
8 NO Switched Relay positive 0-12V
9- 
						

							BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
166 Connector 2
C0635 (24-way, Black)
PIN Wire
ColorDescription Signal
RangePIN Wire
ColorDescription Signal
Range
1 WU HO2S Heater Bank B -
downstream12-0V 13 WO HO2S Heater Bank B -up-
stream12-0V  
2 - 14 G HO2S signal Bank B-down-
stream0-1V  
3 - 15 O HO2S signal Bank A -up-
stream0-1V  
4 - 16 U HO2S signal Bank B -up-
stream0-1V  
5 Thermostat Monitoring
Thermistor Ground 0V 17 Y HO2S signal Bank A -
downstream0-1V  
6 - 18 UP Fuel pump relay [PWM] 12-0V
7 WU HO2S Heater Bank A-
downstream12-0V 19 WO HO2S Heater Bank A -up-
stream12-0V
8 RB HO2S Earth Bank B-
downstream0V 20 -
9 RB HO2S Earth Bank A -up-
stream0V 21 Thermostat Monitoring
Thermistor Signal 0-5V
10 RB HO2S Earth Bank B -up-
stream0V 22 -
11 RB HO2S Earth Bank A-
downstream0V 23 UR Main Relay Output [Earth] 0V
12 -  24 DMTL Pump Motor 12-0V