Engine Management Component Overview
ENGINE MANAGEMENT SYSTEM (EMS) COMPONENT DESCRIPTIONThe engine management system is controlled by the Engine Control Module (ECM) (39) which receives signals from the various EMS sensors, and uses these inputs to modify fuel and ignition settings to provide optimum driveability (i.e. power, refinement) while allowing compliance to emissions standards. In addition a number of other functions are controlled as listed below.
The Intake Air Temperature sensor (IATS) (1) measures the temperature of the air in the induction tract and transmits this to the ECM. Intake air is filtered before entering the induction tract by two air cleaners (2 and 3). Idle air flow can bypass the throttle blades by two idle air control valves (5 and 6).
Throttle position is detected by the Throttle Position Sensor (TPS) (4) which reports to the ECM. The closed throttle position switch (idle switch) is integral to the throttle position sensor.
Excess vapor formed in the fuel tank is absorbed into the evaporative emission purge control canister (9). While the engine is running, the fuel absorbed in the canister is gradually purged back into the engine by manifold depression. The rate of purging is under the control of the evaporative emission purge control solenoid valves (7 and 8) which are controlled by the ECM. This helps control excess hydrocarbon emissions from the vehicle.
The manifold absolute pressure sensors (MAPS) (10 and 12) measure the absolute pressure in each inlet manifold (i.e. relative to vacuum). The pressure signal is transmitted to the ECM as a voltage. This signal is the primary measure of engine load, and is fundamental to fuel and ignition control, as well as being used for other functions of the EMS.
Engine speed is measured by the Engine speed sensor (16) mounted behind the flywheel. This indicates the actual engine rotational speed to the ECM in the form of 12 pulses per engine revolution. The engine speed is used for both fuel and ignition synchronization, as well as other functions.
Engine position is measured by the engine position sensor (or TDC sensor) mounted below the rear of the crankshaft front pulley (15). This sensor provides one pulse every 360° of crankshaft rotation, indicating when the engine is at cylinder 1aTDC position. The Camshaft Position Sensor (CMP) (14) provides one signal every 720° of crankshaft rotation indicating No. 1 A cylinder at TDC prior to the firing stroke. These signals are used by the ECM to control fuel injection and ignition duration and synchronization.
The two fuel pumps (21 and 22) are situated in the fuel tank (20). These supply fuel to the fuel rail. The fuel rail pressure is controlled by a pressure regulator (19) which returns excess fuel to the tank. The pressure regulator is controlled by manifold depression so that fuel delivery pressure is maintained at 3 bar above manifold pressure. The fuel injectors (17 and 18) are located on the fuel rail. The fuel injectors are electrically operated by the ECM. The time over which the injector is open and the fuel rail pressure determine the volume of fuel injected to the manifold.
The tank fuel is measured by the fuel level sensor (23). This signal is used by the ECM as an input to certain diagnostics. The Engine Coolant Temperature Sensor (ECTS) (24) measures engine operating temperature and transmits this to the ECM.
Ignition spark voltages are produced by two ignition coil packs, one per cylinder bank (27 and 28). There are three double ended coils in each pack, and these deliver a spark to two plugs simultaneously. Each coil pack is driven by its own ignition amplifier (25 and 25) which in turn is controlled by the ECM.
The exhaust gas passes from the exhaust manifold to the catalytic converter assembly, where reactions take place to reduce the levels of pollutants at the tail pipe. The Heated Oxygen Sensors (HO2S) (29,and 30 upstream of the catalysts, 31 and 32 downstream) compare the level of oxygen in the exhaust gas to that in the atmosphere and produce an output signal-which is used by the engine closed loop fuel strategy to make fuelling corrections, and thus help control overall emission levels. Also comparison of upstream and downstream signals allows determination of catalyst conversion efficiency. The sensors contain integral heaters (under ECM control) to allow them to reach optimum operating temperature in a short time after engine start.
The secondary air injection system allows decreased catalyst warm-up time, with on overall effect of reduction of vehicle exhaust emissions. The air pump (33) is mechanically driven by the engine when the ECM commands the air pump electrical clutch on via a relay. The ECM also turns on the Vacuum Solenoid Valve (VSV) (35) which in turn activates the secondary Air Injection Switching Valve (ASV) (34) allowing air from the pump to the exhaust manifold. Two check valves (36 and 37) are fitted in each air outlet line to prevent the possibility of reverse flow to the pump.
The ignition supply (38) is the main power supply to the ECM this supply will be disconnected by the inertia switch if the vehicle is subject to a violent deceleration in a collision. The ECM has separate ignition and battery supply inputs. The battery input (41) maintains the ECM memory as long as the vehicle battery is connected.
The following inputs are also used as part of the engine control system:
The ECM sends fuel used information to the instrument pack (40) (for use by the trip computer) and also signals to the pack when a MIL lamp illumination is needed.
Crank signal (42) input informs the ECM that the engine is being cranked and forms part of the "start fuelling" strategy.
Security and locking module (SLCM) (43), inhibits starting (non-federal cars only) until the correct security code is received from the security/locking system ECU.
An input/output link (44) for a generic scan tool or Jaguar Diagnostic Equipment (JDE) is available to assist with fault diagnosis.
The ECM communicates with the Transmission Control Module (TCM) (45) over five lines: Engine speed, torque and throttle position signals are sent to the TCM while The TCM sends vehicle speed (for diagnostic use) and torque reduction signals (to improve gearshift quality) to the ECM.
The air conditioning ECU connection (46) communicates with the ECM (to ensure that air conditioning operation does not affect idle quality (due to the extra engine load imposed by the compressor).
Park/neutral input (47) is used to control idle quality as the transmission selector moves from neutral to drive and back
Power steering pressure switch (48) allows idle speed compensation as the power steering pump places load on the engine
Fig. 1 EMS System Schematic:
1. Intake Air Temperature Sensor
2. A-Bank Air Cleaner
3. B-Bank Air Cleaner
4. Throttle Position Sensor
5. A-Bank Idle Air Control Valve
6. B-Bank Idle Air Control Valve
7. A-Bank Evap. Emission Purge Control Solenoid Valve
8. B-Bank Evap. Emission Purge Control Solenoid Valve
9. Evap. Emission Purge Control Canister
10. A-Bank Manifold Absolute Pressure Sensor
11. A-Bank Fuel Filter
12. B-Bank Manifold Absolute Pressure Sensor
13. B-Bank Fuel Filter
14. Camshaft Position Sensor
15. Engine Position Sensor
16. Engine Speed Sensor
17. A-Bank Fuel Injectors
18. B-Bank Fuel Injectors
19. Fuel Pressure Regulator
20. Fuel Tank
21. Main Fuel Pump
22. Secondary Fuel Pump
23. Fuel Level Sensor
24. Engine Coolant Temperature Sensor
25. A-Bank Ignition Amplifier
26. B-Bank Ignition Amplifier
27. A-Bank Ignition Coil
28. B-Bank Ignition Coil
29. A-Bank Upstream Heated Oxygen Sensor
30. B-Bank Upstream Heated Oxygen Sensor
31. A-Bank Downstream Heated Oxygen Sensor
32. B-Bank Downstream Heated Oxygen Sensor
33. Secondary Air Injection Pump
34. Secondary Air Injection Switching Valve
35. Vacuum Solenoid Valve
36. A-Bank Secondary Air Injection Check Valve
37. B-Bank Secondary Air Injection Check Valve
38. Ignition Supply
39. Engine Control Module
40. Malfunction Indicator Lamp / Instrument Pack
41. Battery
42. Cranking Signal
43. Security and Locking Control Module
44. PDU / Generic Scan Tool
45. Transmission Control Module (5 lines)
46. Air Conditioning Control Module (4 lines)
47. Park Neutral Switch
48. Power Steering Pressure Switch