3-8
04/14/2009 NP10-V8JLR: AJ133 5.0-Liter DFI V8 Engine
Technical Training
Engine Control Module
Engine Management System
ENGINE CONTROL MODULE
The ECM is supplied with battery voltage from a 5A fuse and an ignition supply from the ECM relays through\
a 15A
fuse, both located in the CJB. A regulator located within the ECM supplies a 5V current to internal compone\
nts such
as the microprocessor unit. Other components or functions requiring full\
battery voltage are controlled by external
relays or internal switching modules.
The microprocessor within the ECM receives signals from different components and control modules and uses a pro-
gram within the ECM software to interpret the signal information and issue signals which relate t\
o how the engine
components and functions should be controlled. The ECM communicates with other control modules via bidirectional
Controller Area Network (CAN) communication interfaces.
The ECM uses the following inputs and outputs:
Inputs
• Camshaft position (CMP) sensor
• Crankshaft position (CKP) sensor
• Fuel rail high-pressure sensor
• Mass air flow (MAF) sensors (2)
• Knock sensors (4)
• Engine coolant temperature (ECT) sensor
• Manifold absolute pressure (MAP) sensor
• Electronic throttle position sensor
• Accelerator pedal position (APP) sensor
• Cooling fan speed
• Upstream Universal Heated Exhaust Gas Oxygen (UHEGO) sensors (2)
• Brake switch
• Speed control cancel/suspend switch
• Intake air temperature (IAT) sensor (integrated into the MAF) (2)
• Ambient air temperature (AAT) sensor
• Engine oil level and temperature sensor
• Temperature and manifold absolute pressure (TMAP) sensor (SC only)
Outputs
• Throttle Actuator
• Coil-on-plug (COP) ignition coils (8)
• Upstream Universal Heated Exhaust Gas Oxygen (UHEGO) sensors (2)
• Downstream Heated Oxygen Sensors (HO2S) (2)
• Direct injection fuel injectors (8)
• Variable camshaft timing (VCT) solenoids (4)
• Camshaft profile switching (CPS) solenoids (2)
• Intake manifold tuning solenoid
• Carbon canister purge valve
• Fuel pump relay
• Starter relay
• A/C condenser fan relay
• ECM main relay viscous fan control
• Generator control
• Air flap solenoid (SC only)
• Pump control diagnostics
• Diagnostic Monitoring of Tank Leakage (DMTL)
3-2804/14/2009NP10-V8JLR: AJ133 5.0-Liter DFI V8 EngineTechnical Training
Fuel Tank Canister Purge ValveEngine Management System
FUEL TANK CANISTER PURGE VALVE
To comply with legislation in fuel evaporative loss, the evaporative emissions loss control system is used on all vehicles.
Its purpose is to minimize the evaporative loss of fuel vapor from the fuel system to the atmosphere. This is achieved by
venting the fuel system through a vapor trap – a canister filled with vapor-absorbing charcoal. The charcoal acts like a
sponge and stores the vapor until the canister is purged under the control of the ECM into the engine for combustion. The
carry-over system uses the DMTL system to check for fuel tank integrity.
The canister is connected with the intake manifold, after the throttle body, via a purge valve. This valve is opened and
closed according to a PWM signal from the ECM. The system does not work properly in the case of leakage or clog-
ging within the system or if the purge valve cannot be controlled.
The canister is purged by drawing clean air through the
charcoal, which carries the hydrocarbons into the engine
where they are combusted. To maintain driveability and
emission control, purging must be closely controlled as a
1% concentration of fuel vapor from the canister in the
air intake may shift the air/fuel ratio by as much as 20%.
Purging must be carried out at regular intervals to regen-
erate the charcoal, since the storage capacity is limited.
The purge function is alternated with the fuel metering
adaptation, as both cannot be active at the same time.
The ECM alters the PWM signal to the purge valve to con-
trol the rate of purging of the canister. The purging of the
canister is done in a controlled manner in order to maintain
the correct stoichiometric air/fuel mixture for the engine.
The ECM also ensures that the canister itself is purged
frequently enough to prevent fuel saturation of the char-
coal, which could lead to an excessive buildup of fuel
vapor (and vapor pressure) in the system, increasing the
likelihood of vapor leaks. Failure Modes
• Valve drive open circuit
• Short circuit to battery voltage or ground
• Valve/pipe work blocked
• Valve stuck open
• Pipe work leaking/disconnected
• Noisy valve
Failure Symptoms
• Engine may possibly stall on return to idle (if valve
stuck open)
• Poor idling quality (if valve stuck open)
• Fuel metering adaptations forced excessively rich if canister is clear with valve stuck open
• Fuel metering adaptations forced excessively lean if canister is saturated with valve stuck open
• Saturation of canister (if valve stuck closed)
PURGE VALVE
AIR FLOWS ENS OR
THROTTLE
FUEL TANK CARBON FILTER
INTAKE
MANIFOLD
NP10V8111
