Part 1
Electronic Engine Controls
COMPONENT LOCATION - SHEET 1 OF 3
COMPONENT LOCATION - SHEET 2 OF 3
COMPONENT LOCATION - SHEET 3 OF 3
INTRODUCTION
The EEC (electronic engine control) system operates the engine to generate the output demanded by the accelerator pedal and loads imposed by other systems. The EEC (electronic engine control) system has an ECM (engine control module) that uses a torque-based strategy to evaluate inputs from sensors and other systems, then produces outputs to engine actuators to produce the required torque.
The EEC (electronic engine control) system controls the following:
- Charge air
- Fueling
- Ignition timing
- Valve timing
- Cylinder knock
- Idle speed
- Engine cooling fan
- Evaporative emissions
- On-board diagnostics
- Immobilization system interface
- Speed control.
ENGINE CONTROL MODULE
The ECM (engine control module) is installed in the passenger side protective box in the engine compartment, on a bracket attached to the suspension housing. The bracket also contains an electric cooling fan. The ECM (engine control module), which has an internal temperature sensor, controls the operation of the cooling fan. While the ignition is on, the cooling fan receives a power supply from the EMS relay in the EJB (engine junction box). When cooling is required, the ECM (engine control module) connects the cooling fan to ground.
The ECM has the capability of adapting its fuel and ignition control outputs in response to several sensor inputs.
The ECM (engine control module) receives inputs from the following:
- CKP (crankshaft position) sensor.
- CMP (camshaft position) sensors (4 off).
- ECT (engine coolant temperature) sensors (2 off).
- Knock sensors (4 off).
- MAP (manifold absolute pressure) sensor.
- MAFT (mass air flow and temperature) sensors (2 off).
- Throttle position sensor.
- Heated oxygen sensors (4 off).
- APP (accelerator pedal position) sensor.
- Ambient air temperature sensor.
- FRP (fuel rail pressure) sensor. For additional information, refer to Fuel Charging and Controls Fuel Charging and Controls
- Engine cooling fan. For additional information, refer to Engine Cooling
- Stoplamp switch. For additional information, refer to Anti-Lock Control - Traction Control
- Speed control cancel/suspend switch. For additional information, refer to Speed Control
- Oil level and temperature sensor. For additional information, refer to Engine Description and Operation
- Fuel LP (low pressure) sensor. For additional information, refer to Fuel Tank and Lines Fuel Tank and Lines
- Fuel pump driver module. For additional information, refer to Fuel Tank and Lines Fuel Tank and Lines
The ECM (engine control module) provides outputs to the following:
- Electronic throttle.
- Main relay.
- Heaters elements of the heated oxygen sensors (4 off).
- Fuel injectors (8 off). For additional information, refer to Fuel Charging and Controls Fuel Charging and Controls
- Ignition coils (8 off). For additional information, refer to Engine Ignition Description and Operation
- VCT (variable camshaft timing) solenoids (4 off). For additional information, refer to Engine Description and Operation
- Camshaft profile switching solenoids (2 off). For additional information, refer to Engine Description and Operation
- Variable intake system tuning valve. For additional information, refer to Intake Air Distribution and Filtering Intake Air Distribution and Filtering
- EVAP (evaporative emission) canister purge valve. For additional information, refer to 303-15: Evaporative Emissions - 5.0L, Description and Operation.
- Engine starter relay. For additional information, refer to Starting System Description and Operation
- Engine cooling fan. For additional information, refer to Engine Cooling
- Generator. For additional information, refer to Generator
- HP fuel pumps. For additional information, refer to Fuel Charging and Controls Fuel Charging and Controls
- Fuel pump driver module. For additional information, refer to Fuel Tank and Lines Fuel Tank and Lines
- DMTL (diagnostic module - tank leakage). For additional information, refer to 303-15: Evaporative Emissions - 5.0L, Description and Operation.
CRANKSHAFT POSITION SENSOR
The CKP (crankshaft position) sensor is an inductive sensor that allows the ECM (engine control module) to determine the angular position of the crankshaft and the engine speed.
The CKP (crankshaft position) sensor is installed in the rear left side of the sump body, in line with the engine drive plate. The sensor is secured with a single screw and sealed with an O-ring. A two pin electrical connector provides the interface with the engine harness.
The head of the CKP (crankshaft position) sensor faces a reluctor ring pressed into the outer circumference of the engine drive plate. The reluctor ring has a 60 minus 2 tooth pattern. There are 58 teeth at 6° intervals, with two teeth removed to provide a reference point with a centerline that is 21° BTDC (before top dead center) on cylinder 1 of bank A.
If the CKP (crankshaft position) sensor fails, the ECM (engine control module):
- Uses signals from the CMP (camshaft position) sensors to determine the angular position of the crankshaft and the engine speed
- Adopts a limp home mode where engine speed is limited to a maximum of 3000 rev/min.
With a failed CKP (crankshaft position) sensor, engine starts will require a long crank time while the ECM (engine control module) determines the angular position of the crankshaft.
CAMSHAFT POSITION SENSORS
The CMP (camshaft position) sensors are MRE (magneto resistive element) sensors that allow the ECM (engine control module) to determine the angular position of the camshafts. MRE sensors produce a digital output which allows the ECM (engine control module) to detect speeds down to zero.
The four CMP (camshaft position) sensors are installed in the front upper timing covers, one for each camshaft.
Each CMP (camshaft position) sensor is secured with a single screw and sealed with an O-ring. On each CMP (camshaft position) sensor, a three pin electrical connector provides the interface with the engine harness.
The head of each CMP (camshaft position) sensor faces a sensor wheel attached to the front of the related VCT (variable camshaft timing) unit.
If a CMP (camshaft position) sensor fails, the ECM (engine control module):
- Defaults to base mapping for the ignition timing, with no cylinder correction
- Disables the VCT (variable camshaft timing) system.
ENGINE COOLANT TEMPERATURE SENSORS
The ECT (engine coolant temperature) sensors are NTC (negative temperature coefficient) thermistors that allow the ECM (engine control module) to monitor the engine coolant temperature.
There are two identical ECT (engine coolant temperature) sensors installed, which are identified as ECT 1 and ECT 2. Each sensor is secured with a twist-lock and latch mechanism, and is sealed with an O-ring. A two pin electrical connector provides the interface between the sensor and the engine harness.
ECT 1
ECT 1 is installed in the heater manifold, at the rear of the RH (right-hand) cylinder head. The input from this sensor is used in calibration tables and by other systems.
If there is an ECT 1 fault, the ECM (engine control module) adopts an estimated coolant temperature. On the second consecutive trip with an ECT 1 fault, the ECM (engine control module) illuminates the MIL (malfunction indicator lamp).
ECT 2
ECT 2 is installed in the lower hose connector which attaches to the bottom of the thermostat. The input from this sensor is used for OBD (on-board diagnostic) 2 diagnostics and, in conjunction with the input from ECT 1, to confirm that the thermostat is functional.
If there is an ECT 2 fault, the ECM (engine control module) illuminates the MIL (malfunction indicator lamp) on the second consecutive trip.
KNOCK SENSORS
The knock sensors are piezo-ceramic sensors that allow the ECM (engine control module) to employ active knock control and prevent engine damage from pre-ignition or detonation.
Two knock sensors are installed on the inboard side of each cylinder head, one mid-way between cylinders 1 and 2, and one mid-way between cylinders 3 and 4. Each knock sensor is secured with a single screw. On each knock sensor, a two pin electrical connector provides the interface with the engine harness.
The ECM (engine control module) compares the signals from the knock sensors with mapped values stored in memory to determine when detonation occurs on individual cylinders. When detonation is detected, the ECM (engine control module) retards the ignition timing on that cylinder for a number of engine cycles, then gradually returns it to the original setting.
The ECM (engine control module) cancels closed loop control of the ignition system if the signal received from a knock sensor becomes implausible. In these circumstances the ECM (engine control module) defaults to base mapping for the ignition timing. This ensures the engine will not become damaged if low quality fuel is used. The MIL (malfunction indicator lamp) will not illuminate, although the driver may notice that the engine 'pinks' in some driving conditions and displays a drop in performance and smoothness.
The ECM calculates the default value if one sensor fails on each bank of cylinders.
MANIFOLD ABSOLUTE PRESSURE SENSOR
The MAP (manifold absolute pressure) sensor allows the ECM (engine control module) to calculate the load on the engine, which is used in the calculation of fuel injection time.
The MAP (manifold absolute pressure) sensor is installed in the air inlet of the intake manifold. The sensor is secured with a single screw and sealed with an O-ring. A three pin electrical connector provides the interface with the engine harness.
If the MAP (manifold absolute pressure) sensor fails, the ECM (engine control module) adopts a default value of 1 bar (14.5 lbf/in.2).
With a failed MAP (manifold absolute pressure) sensor, the engine will suffer from poor starting, rough running and poor driveability.
MASS AIR FLOW AND TEMPERATURE SENSORS
The MAFT (mass air flow and temperature) sensors allow the ECM (engine control module) to measure the mass and the temperature of the air flow into the engine. The mass air flow is measured with a hot film element in the sensor. The temperature of the air flow is measured with a NTC (negative temperature coefficient) thermistor in the sensor. The mass air flow is used to determine the fuel quantity to be injected in order to maintain the stoichiometric air:fuel mixture required for correct operation of the engine and the catalytic converters.
There are two MAFT (mass air flow and temperature) sensors installed, one in each air cleaner outlet duct. Each MAFT (mass air flow and temperature) sensor is secured with two screws and sealed with an O-ring. On each MAFT (mass air flow and temperature) sensor, a five pin electrical connector provides the interface with the engine harness.
If the hot film element signal fails the ECM (engine control module) invokes a software backup strategy to calculate the mass air flow from other inputs. Closed loop fuel control, closed loop idle speed control and evaporative emissions control are discontinued. The engine will suffer from poor starting, poor throttle response and, if the failure occurs while driving, the engine speed may dip before recovering.
If the NTC (negative temperature coefficient) thermistor signal fails the ECM (engine control module) adopts a default value of 25 °C (77 °F) for the intake air temperature.
THROTTLE POSITION SENSORS
The TP (throttle position) sensors allow the ECM (engine control module) to determine the position and angular rate of change of the throttle blade.
There are two TP (throttle position) sensors located in the electronic throttle. See below for details of the electronic throttle.
If a TP (throttle position) sensor fails, the ECM (engine control module):
- Adopts a limp home mode where engine speed is limited to a maximum of approximately 2000 rev/min
- Discontinues evaporative emissions control
- Discontinues closed loop control of engine idle speed.
With a failed TP (throttle position) sensor, the engine will suffer from poor running and throttle response.