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 137
BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Introduction
Bosch supplies the engine management system used on Discovery Series II and Range Rover 
beginning mid 1999 model year. It is referred to as the Bosch Motronic 5.2.1 system. The 
system supports  sequential fuel injection and waste spark ignition. The system is designed to 
optimize the performance and efficiency of the engine.
The key functions of the Bosch 5.2.1 engine...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
138System Components
1. Mass Airflow & Temperature 
Sensor8. Idle Air Control Valve
2. Fuel Injectors 9. Ignition Coils
3. Spark Plugs/High Tension Leads 10. Engine Coolant Temperature 
Sensor
4. Fuel Pump Relay 11. Crankshaft Speed and Position 
Sensor
5. A/C Compressor Clutch & Cool-
ing Fan Relay12. Knock Sensor
6. Throttle Position Sensor 13. Camshaft Position Sensor
7. Heated Oxygen Sensor 

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 139 System Inputs
The Bosch 5.2.1 system optimizes engine performance by interpreting signals from numerous 
vehicle sensors and other inputs. Some of these signals are produced by the actions of the 
driver, some are supplied by sensors located on and around the engine and some are supplied 
by other vehicle systems. 
The inputs are as follows:
•  Ignition switch (position II)
•  Throttle position sensor (TPS)
•  Crankshaft...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
140 The ECM is programmed during manufacture by writing the program and the engine ‘tune’ into 
the Flash EPROM (erasable programmable read only memory). This Flash EPROM can be 
reprogrammed in service, using TestBook. In certain circumstances, it is possible to alter the 
‘tune’ or functionality of the ECM using this process.
The engine management system (EMS) now used on Discovery Series II , is an  improvement 
over existing systems. The new EMS now improves the...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 141 Freeze frame data always records:
•  Engine speed 
•  Engine load 
•  ‘P’ code
•  Short term fuelling trim A / B
•  Long term fuelling trim A / B
•  Fuelling status A / B
•  Coolant temp
•  Road speed
The ECM will illuminate the malfunction indicator lamp (MIL) on detection of a fault, providing 
the fault has occurred on two consecutive driving cycles. This strategy ‘validates’ the fault, 
ensuring that the MIL does not...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
142 The throttle position sensor is a potentiometer. It receives a 5 volt supply from the ECM 
whenever the ignition switch is turned ‘on’. It then returns a proportion of the supplied voltage to 
the ECM to indicate its position and rate of movement. The actual position of the throttle valve, 
the direction in which it is moving (if it is moving) and, if so, the rate at which it is moving will 
determine the value of the voltage returned. The returned voltage will be...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 143 Crankshaft position sensor
The crankshaft position sensor is located in the engine 
block, just below number 7 cylinder (see figure 51). It 
protrudes through the cylinder block and is positioned 
adjacent to the face of the flywheel or flex plate. The 
sensor reacts to a ‘drilled reluctor’ incorporated into the 
flex plate to ascertain engine speed and position 
information. The sensor is located on a spacer and is 
secured in...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
144 The crankshaft sensor is an inductive type sensor which produces a sinusoidal output voltage 
signal. The following illustration shows a typical crankshaft signal over a 480° crankshaft 
revolution. This voltage is induced by the proximity of the moving toothed reluctor, which excites 
the magnetic flux around the tip of the sensor when each tooth passes. This output voltage will 
increase in magnitude and frequency as the engine rpm rises and the speed at which...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
Bosch 5.2.1 Engine Management System 145 Camshaft position sensor
The camshaft position sensor is located in the timing cover and the tip of the sensor is 
positioned in close proximity to the camshaft gear. The camshaft gear incorporates four teeth. 
The camshaft position sensor is a hall-effect sensor which switches a battery fed supply ‘on’ 
and ‘off’. The supply is switched when the teeth machined onto the camshaft gear pass by the 
tip of the sensor. The four...

BOSCH 5.2.1 ENGINE MANAGEMENT SYSTEM
146 In addition, the ECM will store a relevant fault code and capture the input signal supplied by the 
engine coolant temperature sensor, and the engine load calculation and the engine rpm at the 
time of failure. TestBook will display the live readings from the camshaft sensor.    
Engine coolant temperature sensor
The engine coolant temperature sensor is located near the 
top of the engine, adjacent to the coolant outlet pipe. The 
sensor features four electrical...