Updated Engine Management Description
Engine Management
The new Engine Management Systems (EMS) for the 4.0 Litre AJ16 engine has variations to meet the exhaust emissions and on-board diagnostic requirements for markets in Europe, North America, and the Rest of the World (ROW) (see On-board Diagnostics under Powertrain Management). The variants for North America comply with the comprehensive emissions monitoring demanded by the California Air Resources Board (CARB) On-board Diagnostic II regulations.
Features
Some components are carried over from the previous model year and a substantial number of new components are introduced. The new AJ16 EMS system provides a number of features that offer significant improvements in engine performance and reduced exhaust emissions:
Sequential Fuel Injection - optimizes injection time on and provides cylinder-to-cylinder air flow corrections, idle stability and reduced emissions.
Knock Sensing - Prevents audible knock, improves power, provides greater tolerance to variations in engine build and reduces the potential for engine damage due to poor fuel quality.
Adaptive Fuelling - Optimizes fuelling over the life of the engine.
Improved Purge Control - Required to meet the more stringent legislative requirements.
Hardware Changes
Some hardware is carried over from the previous model year. The bulk is new or modified.
Carried Over Components
Intake Air Temperature Sensor - The intake air temperature sensor is installed in the intake manifold elbow.
Coolant Thermistor - The Coolant Thermistor remains in its current vehicle position in the thermostat housing.
Modified Components
Fuel Injectors - The 6 fuel injectors are similar to those used in the previous model year. The flow rates are changed. Each consists of a solenoid, core, disc valve and housing. When the "ON" control signal from the Engine Control Module is applied to the solenoid coil, the disc valve lifts up and fuel is injected into the intake port. The quantity of injected fuel is determined by the time that the "ON" signal is applied to the coil.
Crankshaft Sensor - The length of the crankshaft sensor electrical flying lead is reduced and is fitted with a new connector and connector clipping bracket.
Exhaust Gas Recirculation Check Sensor - The length of the electrical flying lead of the Exhaust Gas Recirculation (EGR) check sensor (North America only) is increased.
New Components
Engine Control Module (ECM) 12/24Mhz 1.5 Mbit - This replaces the previous 15 CU 8Kbit module. The increased capacity is provided to meet the demands made by the CARB OBD II regulations.
On-Plug Ignition Coils - The HT leads, distributor and ignition coil are replaced by individual ignition coils that clip directly onto the spark plugs.
Mass Air Flow Sensor - A new sensor of improved design with a calibration range that encompasses normally aspirated and supercharged engines.
Purge Valve - A new Purge Valve with improved flow control is specified.
Electric Air Pump - This replaces the mechanical pump, belt assembly and solenoid vacuum valve. It is a much simpler arrangement with fewer parts, and reduces parasitic power losses on the engine.
Electric Exhaust Gas Recirculation Valve (EGR) - This replaces the mechanical vacuum EGR valve and solenoid vacuum valve. The new arrangement provides accurate position feedback and consequently greater control of valve movement over its operating range.
The EGR is cycled through its operating range when the ignition is switched off in order to prevent carbon build-up.
Heated Oxygen (HO2S) Sensors - North American vehicles - 4 sensors are fitted, 2 upstream and 2 downstream of the first two catalysts: one per bank of three cylinders. Rest of the World have 2 downstream as on previous model year vehicles.
Knock Sensor - Two sensors are added to the system to optimize ignition timing, improve idle stability and prevent engine damage due to poor fuel quality.
Engine Position Sensor - This is added to the system in order to synchronize operation of the fuel injectors and ignition. It serves the same function as a camshaft sensor; i.e. runs at half engine speed.
Throttle Body Assembly - This replaces the throttle body assembly and separate idle speed control valve previously installed. The new assembly incorporates a new idle speed control valve and a new single track, non-adjustable, throttle potentiometer.
Component Locations
ECM Pin-Out
System Overview
The Electronic Control Module (ECM) receives and processes signals from a number of sensors, then modifies the fuel and ignition settings to maintain the correct stoichiometric fuel and air mixture under all conditions.
Note: All sensors input signals to the ECM.
Component Descriptions
Mass Air Flow Sensor (MAFS) - Measures the quantity of air drawn into the engine.
Intake Air Temperature Sensor (IAT) - Measures the temperature of the air in the induction tract.
Idle Speed Control Valve (ISC) - Directed by the ECM to govern engine idle speed in conjunction with ignition timing control.
Engine Coolant Temperature Sensor (ECT) - Monitors engine coolant temperature.
Fuel Pump - Situated in the fuel tank, supplies fuel to the injectors via the fuel rail and pressure regulator.
Spark Plugs and Ignition Coils - Each spark plug is fitted with its own ignition coil. Ignition timing is varied according to the engine speed and load.
Heated Oxygen (HO2S) Sensors - Continually monitor exhaust gases entering and leaving the first catalysts. From the output of the downstream sensors, the ECM adjusts the fuel settings to reduce emissions from the exhaust. The sensors integral heaters accelerate the warm-up period on start-up, and allow the tip temperature to be controlled accurately. In order to meet CARB OBD II requirements, North American vehicles have 4 sensors: 2 upstream and 2 downstream. By comparing the output of the sensors upstream and downstream, the ECM can determine the efficiency of the first catalysts.
Throttle Potentiometer (TP) - Measures the position of the throttle.
Exhaust Gas Recirculation Valve (EGR) - Activated by the ECM to introduce exhaust gas into the intake air stream to dilute the intake fuel/air mixture. This lowers the combustion temperature and reduces the formation of nitrous oxide. The temperature of the gasses is monitored by the EGR Function Sensor.
Knock Sensors (KS) - Detects combustion knock is specific cylinders. If knock is detected the ECM will retard the ignition timing for the cylinder which is knocking.
Crankshaft Position Sensor (CKP) - Measures engine speed and crankshaft position for accurate ignition timing. By monitoring differences in crankshaft acceleration between cylinders, it also detects ignition misfires.
Engine Position Sensor (CMP) - This signal allows the ECM to synchronize operation of the fuel injectors and ignition.
Secondary Air Injection Pump (AIR) - Is switched on via a relay by the ECM to provide additional air to reduce the level of carbon monoxide (C0) and hydrocarbons (HC) in the exhaust gasses during warm up. The additional aid rapidly accelerates the rise in exhaust gas temperature to the catalyst operating temperature level. The relay also energizes the solenoid operating the integral stop valve, opening the air line through the mechanical check valve to the exhaust manifold.
Fuel Tank - Maximum fuel capacity is 90% of tank capacity. As fuel is withdrawn from the tank the volume of fuel laden air (vapor) expands and is vented to the atmosphere through an Activated Charcoal Canister which absorbs the fuel.
Canister Purge Valve - Is activated by the ECM to open the canister line to intake manifold vacuum, drawing air through the activated charcoal canister and carrying fuel vapor into the intake manifold.
Fuel Level Sensor - Measures the level of fuel in the tank.
The remaining signals input to the ECM are: The Park/Neutral Switch; the Security CM, and Ignition ON.
The remaining signals output by the ECM are: Road Speed (Instrument Pack); Trip Computer; Malfunction Indicator Lamp (Engine Fault); Diagnostic Interface; Transmission Control Module (TCM).
The Inertia Switch disconnects electrical power when the vehicle is subjected to a sudden deceleration/acceleration.
Emission Control Standards (ECS)
The engine management system described above is designed to meet the Federal Type A emissions control standards. Standards are classified according to the level of emissions and diagnostics an engine is expected to meet. The emission control standards that AJ16 engines meet list in the table.