I stumbled onto this while looking through the 2006 Service Manual.
This is an interesting explanation of the Open/Closed Loop operation.
I am a new-be in this area and found this information interesting and informative.
I had to break it into 3 messages because it is too long.
² Air/fuel ratio
² Emission control devices
² Cooling fan
² Charging system
² Idle speed
² Vehicle speed control
Various sensors provide the inputs necessary for the PCM to correctly operate these systems. In addition to the sensors, various switches also provide inputs to the PCM.
MODES OF OPERATION
For the PCM to enter CLOSED LOOP operation, the following must occur:
² If the coolant is over 50°F the PCM will wait 15 seconds.
² If the coolant is over 167°F the PCM will wait 3 seconds.
2. For other temperatures the PCM will interpolate the correct waiting time.
3. O2 sensor must read either greater than 0.745 volts or less than 0.29 volt.
4. The multi-port fuel injection systems has the following modes of operation:
² Ignition switch ON (Zero RPM)
² Engine start-up
² Engine warm-up
² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
5. The engine start-up (crank), engine warm-up, deceleration with fuel shutoff and wide open throttle modes are OPEN LOOP modes. Under most operating conditions, the acceleration, deceleration (with A/C on), idle and cruise modes, with the engine at operating temperatureare CLOSED LOOP modes.
² The PCM determines atmospheric air pressure from the MAP sensor input to modify injector pulse width.
When the key is in the ON position and the engine is not running (zero rpm), the Auto Shutdown (ASD) and fuel pump relays de-energize after approximately 1 second. Therefore, battery voltage is not supplied to the fuel pump, ignition coil, fuel injectors and heated oxygen sensors.
ENGINE START-UP MODE
The following actions occur when the starter motor is engaged.
² If the PCM receives the camshaft position sensor and crankshaft position sensor signals, it energizes the Auto Shutdown (ASD) relay and fuel pump relay. If the PCM does not receive both signals within approximately one second, it will not energize the ASD relay and fuel pump relay. The ASD and fuel pump relays supply battery voltage to the fuel pump, fuel injectors, ignition coil, (EGR solenoid and PCV heater if equipped) and heated oxygen sensors.
² The PCM energizes the injectors (on the 69° degree falling edge) for a calculated pulse width until it determines crankshaft position from the camshaft position sensor and crankshaft position sensor signals. The PCM determines crankshaft position within 1 engine revolution.
² After determining crankshaft position, the PCM begins energizing the injectors in sequence. It adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to the injectors On and Off.
² When the engine idles within ±64 RPM of its target RPM, the PCM compares current MAP sensor value with the atmospheric pressure value received during the Ignition Switch On (zero RPM) mode.
² Engine RPM
² Battery voltage
² Engine coolant temperature
² Inlet/Intake air temperature (IAT)
² Throttle position
² The number of engine revolutions since cranking was initiated
ENGINE WARM-UP MODE
² Crankshaft position (engine speed)
² Engine coolant temperature
² Inlet/Intake air temperature (IAT)
² Throttle position
² A/C switch status
² Battery voltage
² Vehicle speed
² Speed control
² O2 sensors
The PCM adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to the injectors On and Off.
continued in next message
This is an interesting explanation of the Open/Closed Loop operation.
I am a new-be in this area and found this information interesting and informative.
I had to break it into 3 messages because it is too long.
FUEL INJECTION
OPERATION
INJECTION SYSTEM
All engines used in this section have a sequential Multi-Port Electronic Fuel Injection system. The MPI system is computer regulated and provides precise air/fuel ratios for all driving conditions. The Powertrain Control Module (PCM) operates the fuel injection system.
OPERATION
INJECTION SYSTEM
All engines used in this section have a sequential Multi-Port Electronic Fuel Injection system. The MPI system is computer regulated and provides precise air/fuel ratios for all driving conditions. The Powertrain Control Module (PCM) operates the fuel injection system.
The PCM regulates:
² Ignition timing² Air/fuel ratio
² Emission control devices
² Cooling fan
² Charging system
² Idle speed
² Vehicle speed control
Various sensors provide the inputs necessary for the PCM to correctly operate these systems. In addition to the sensors, various switches also provide inputs to the PCM.
The PCM can adapt its programming to meet changing operating conditions.
Fuel is injected into the intake port above the intake valve in precise metered amounts through electrically operated injectors. The PCM fires the injectors in a specific sequence. Under most operating conditions, the PCM maintains an air fuel ratio of 14.7 parts air to 1 part fuel by constantly adjusting injector pulse width. Injector pulse width is the length of time the injector is open.
The PCM adjusts injector pulse width by opening and closing the ground path to the injector. Engine RPM (speed) and manifold absolute pressure (air density) are the primary inputs that determine injector pulse width.
MODES OF OPERATION
As input signals to the PCM change, the PCM adjusts its response to output devices. For example, the PCM must calculate a different injector pulse width and ignition timing for idle than it does for Wide Open Throttle (WOT).
There are several different modes of operation that determine how the PCM responds to the various input signals.
There are two different areas of operation, OPEN LOOP and CLOSED LOOP.
During OPEN LOOP modes the PCM receives input signals and responds according to preset PCM programming.
Inputs from the upstream and downstream heated oxygen sensors are not monitored during OPEN LOOP modes, except for heated oxygen sensor diagnostics (they are checked for shorted conditions at all times).
During CLOSED LOOP modes the PCM monitors the inputs from the upstream and downstream heated oxygen sensors. The upstream heated oxygen sensor input tells the PCM if the calculated injector pulse width resulted in the ideal air-fuel ratio of 14.7 to one. By monitoring the exhaust oxygen content through the upstream heated oxygen sensor, the PCM can fine tune injector pulse width. Fine tuning injector pulse width allows the PCM to achieve optimum fuel economy combined with low emissions.
For the PCM to enter CLOSED LOOP operation, the following must occur:
1. Engine coolant temperature must be over 35°F.
² If the coolant is over 35°F the PCM will wait 38 seconds.² If the coolant is over 50°F the PCM will wait 15 seconds.
² If the coolant is over 167°F the PCM will wait 3 seconds.
2. For other temperatures the PCM will interpolate the correct waiting time.
3. O2 sensor must read either greater than 0.745 volts or less than 0.29 volt.
4. The multi-port fuel injection systems has the following modes of operation:
² Ignition switch ON (Zero RPM)
² Engine start-up
² Engine warm-up
² Cruise
² Idle² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
5. The engine start-up (crank), engine warm-up, deceleration with fuel shutoff and wide open throttle modes are OPEN LOOP modes. Under most operating conditions, the acceleration, deceleration (with A/C on), idle and cruise modes, with the engine at operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injection system, the following actions occur:
² The PCM monitors the engine coolant temperature sensor and throttle position sensor input. The PCM determines basic fuel injector pulse width from this input.² The PCM determines atmospheric air pressure from the MAP sensor input to modify injector pulse width.
When the key is in the ON position and the engine is not running (zero rpm), the Auto Shutdown (ASD) and fuel pump relays de-energize after approximately 1 second. Therefore, battery voltage is not supplied to the fuel pump, ignition coil, fuel injectors and heated oxygen sensors.
ENGINE START-UP MODE
This is an OPEN LOOP mode. If the vehicle is in park or neutral (automatic transaxles) or the clutch pedal is depressed (manual transaxles) the ignition switch energizes the starter relay when the engine is not running.
The following actions occur when the starter motor is engaged.
² If the PCM receives the camshaft position sensor and crankshaft position sensor signals, it energizes the Auto Shutdown (ASD) relay and fuel pump relay. If the PCM does not receive both signals within approximately one second, it will not energize the ASD relay and fuel pump relay. The ASD and fuel pump relays supply battery voltage to the fuel pump, fuel injectors, ignition coil, (EGR solenoid and PCV heater if equipped) and heated oxygen sensors.
² The PCM energizes the injectors (on the 69° degree falling edge) for a calculated pulse width until it determines crankshaft position from the camshaft position sensor and crankshaft position sensor signals. The PCM determines crankshaft position within 1 engine revolution.
² After determining crankshaft position, the PCM begins energizing the injectors in sequence. It adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to the injectors On and Off.
² When the engine idles within ±64 RPM of its target RPM, the PCM compares current MAP sensor value with the atmospheric pressure value received during the Ignition Switch On (zero RPM) mode.
Once the ASD and fuel pump relays have been energized, the PCM determines injector pulse width based on the following:
² MAP² Engine RPM
² Battery voltage
² Engine coolant temperature
² Inlet/Intake air temperature (IAT)
² Throttle position
² The number of engine revolutions since cranking was initiated
During Start-up the PCM maintains ignition timing at 9° BTDC.
ENGINE WARM-UP MODE
This is an OPEN LOOP mode. The following inputs are received by the PCM:
² Manifold Absolute Pressure (MAP)² Crankshaft position (engine speed)
² Engine coolant temperature
² Inlet/Intake air temperature (IAT)
² Camshaft position
² Knock sensor² Throttle position
² A/C switch status
² Battery voltage
² Vehicle speed
² Speed control
² O2 sensors
The PCM adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to the injectors On and Off.
The PCM adjusts ignition timing and engine idle speed. Engine idle speed is adjusted through the idle air control motor.
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