It occured to me that many of us come here to find information about our cars.. to potentially understand what and how the car functions...so I thought it helpful to post some info I located that may or may not be valuable to some..:when trying to diagnose your car.. I have more on other areas...if anyone would like it..
Perhaps another forum might be best.., wasn't sure, so will leave this up to the admin types...I hope this helps...
AIR INDUCTION SYSTEM
TURBOCHARGERS
On turbo models, a turbocharger and wastegate assembly are
mounted on the exhaust manifold. At idle and light throttle, the turbo
engine operates like a standard engine. When more power is required,
exhaust gases spin the impeller and turbine. Exhaust flow and
turbocharger RPM increase as engine RPM increases. As turbocharger RPM
increases, boost pressure also increases.
The wastegate is the system safety valve, preventing
excessive boost pressure which can cause engine damage. A signal from
the ECM energizes a solenoid which opens the wastegate to control
optimum boost pressure. In the event of control system failure, the
wastegate will open automatically to limit boost pressure.
Turbocharger operation requires a supply of clean oil. Engine
oil pressure provides lubrication to the system.
COMPUTERIZED ENGINE CONTROLS
Electronic components used in control systems are designed
to carry very low voltages. As little as a 30-volt charge
created by static electricity can cause a total or degrading
failure in the ECM or other electronic components containing
integrated circuits. Before servicing such components,
ground yourself and ground the work area to discharge stored
static electricity. Repeat grounding process periodically
during service procedure.
ENGINE CONTROL MODULE (ECM) (ECU)
On Motronic system, ECM is located under right side of
instrument panel. On Trionic system, ECM is located under right side
of instrument panel. For ECM pin and wire color identification, see
L - WIRING DIAGRAMS article. (which I also have if interested..)
ECM controls all engine functions: fuel injection, ignition
timing, idle speed, emission control, combustion analysis and selfdiagnostics.
On Motronic system, knock sensor functions are provided
by separate knock sensors. Trionic system has knock control but has no
external knock sensor.
NOTE: Components are grouped into 2 categories. The first category
is INPUT DEVICES, which are components that control or
produce voltage signals monitored by the control unit. The
second category is OUTPUT SIGNALS, which are components
controlled by the control unit.
INPUT DEVICES
Vehicles are equipped with different combinations of input
devices. Not all devices are used on all models. To determine the
input device usage on a specific model, see appropriate wiring diagram
in L - WIRING DIAGRAMS article. The available input signals include:
1. A/C Switch
When A/C is on, switch sends a signal to the fuel injection
ECM. The ECM sends a signal to the Idle Air Control (IAC) valve to
increase idle speed to compensate for increased load.
2. Coolant Temperature Sensor (CTS)
The CTS is located on the intake manifold flange. It
transmits an engine temperature signal to the fuel injection ECM. If
the ECM fails to receive this signal, it defaults to an assumed engine
temperature of 113
3. Knock Sensor (Motronic System)
This sensor is located in the engine block, below the intake
manifold. When knocking occurs, it sends a signal to the ignition and
APC ECMs. V6 applications require 2 sensors, one in each exhaust
manifold.
4. Gear Selector Switch
A/T models are equipped with a switch that signals the fuel
injection ECM whenever the transmission is in a range other than Park
or Neutral. The ECM signals the Automatic Idle Control (AIC) valve to
increase idle speed.
5. Heated Oxygen Sensor (HO2S)
This sensor measures quantity of free oxygen in the exhaust
gas. The ECM uses a signal from this sensor to adjust fuel mixture.
This sensor is located in the exhaust manifold and after TWC. The
electric heating element provides improved cold engine driveability.
6. Intake Air Temperature (IAT) Sensor
This sensor is used together with a MAP sensor to provide air
density information to the ECM. IAT is located on the intake air duct
leading to the throttle body.
7. Manifold Absolute Pressure (MAP) Sensor
This sensor is used together with the IAT sensor to provide
air density information to the ECM on some models. It is located on
firewall, toward the right side.
8. Mass Airflow (MAF) Sensor
The MAF sensor is located between the air cleaner and
throttle body. Sensor contains a ceramic plate which is heated
electrically to 356
9. Throttle Position (TP) Sensor
This sensor is located on the throttle body. It transmits
throttle position to the ECM.
Vehicle Speed Sensor (VSS)
On Motronic system, speedometer sends a speed signal to ECM.
On Trionic system, ABS control module sends a speed signal to ECM.
OUTPUT SIGNALS
NOTE: Vehicles are equipped with different combinations of
computer-controlled components. Not all components listed
below are used on every vehicle. For theory and operation on
each output component, refer to the system indicated after
component.
Idle Air Control (IAC) Valve
Canister Purge Solenoid
CHECK ENGINE Light
Fuel Pump Relay
Fuel Injectors
Idle-Up Solenoid
Ignition Coil(s)
Heated Oxygen Sensor
Secondary Air Injection Pump
Self-Diagnostics
Wastegate Solenoid
FUEL SYSTEM
FUEL DELIVERY
The fuel system consists of a fuel tank, fuel pump, fuel
lines, filter and a fuel pressure regulator. Fuel is supplied to each
injector at a constant pressure.
Fuel Pressure Regulator
Fuel pressure regulator, located on fuel rail, maintains
constant fuel pressure at fuel injectors. Excess fuel by-passes
injectors and returns to fuel tank.
Fuel Pump
Fuel pump is located in fuel tank. Fuel is strained through a
mesh screen before entering the pump. A check valve, located on outlet
side of pump, maintains pressure within the fuel system when engine is
off.
Fuel Pump Relay
Fuel pump relay supplies power to fuel pump. It is controlled
by the ECM.
FUEL CONTROL
ECM
ECM processes pulses from the crankshaft position sensor to
determine basic fuel injection timing. It also processes signals from
other sensors for calculating pulse duration to control fuel mixture.
Fuel Injectors
Fuel injectors, located in the intake manifold, spray
atomized fuel directly toward associated intake valves. All injectors
are supplied with fuel from a common fuel manifold. A signal from the
ECM controls injection pulse duration.
Heated Oxygen Sensor
The ECM sends a signal to a heating element in the oxygen
sensor. The function of the heating element is to more quickly bring
the sensing element to operating temperature.
IDLE SPEED
Idle Air Control (IAC) Valve
The IAC valve consists of an air control valve and integral
solenoid. This system provides a more stable idle speed during warm
and cold engine operation. The ECM sends a signal to the IAC valve to
control the amount of air by-passing the throttle valve.
IGNITION SYSTEM
MOTRONIC IGNITION SYSTEM
Motronic 4.1 engine control system used on 2.3L vehicles is a
conventional inductive ignition system with ignition coil and
distributor. On all other Motronic engine control system equipped
vehicles, ignition system is an inductive distributorless ignition
systems incorporating an ignition coil module.
TRIONIC IGNITION SYSTEM
The Trionic system is a distributorless capacitive discharge
type. Components include an ignition cartridge, Hall Effect sensor and
knock sensor. Each spark plug has a separate coil. Energy for the
spark is stored in a capacitor and discharged through the ignition
coil upon a signal from the ECM.
When ignition is switched on, both main relay and fuel pump
relay operate for a few seconds. As soon as ECM senses that crankshaft
has begun to rotate, coolant temperature dependent fuel injection
takes place through injectors simultaneously. This enables short
starting times to be achieved. If engine is started and shortly
afterward switched off again, a fresh pre-injection sequence will be
obtained if 45 seconds is allowed to pass with ignition switched off.
EMISSION SYSTEMS
Pulsed Secondary Air Injection
The pulse air injection system sends air to the exhaust
manifold to reduce exhaust emissions (HC and CO). Components of the
system include check valves, air injection manifolds, a nozzle by each
exhaust valve and an air supply hose from the air cleaner. Filtered
air from the air cleaner flows through the pulse air valves by means
of exhaust manifold pressure variation. Check valves prevent exhaust
gases from flowing back into the air cleaner.
Three-Way Catalytic Converter
All vehicles are equipped with a 3-way catalytic converter.
This device frees oxygen from oxides of nitrogen and oxidizes
hydrocarbons and carbon monoxide.
Fuel Evaporative System
Fumes from the fuel tank are stored in a charcoal canister
when the vehicle is not running. When the engine is started, intake
manifold vacuum purges these fumes through a canister purge solenoid,
upon a signal from the ECM. The canister is located in the left front
of the engine compartment.
A rollover valve in the fuel evaporation line closes if the
vehicle rolls over. It is located in the evaporation line, above the
fuel tank. A vacuum relief valve in the fuel filler cap bleeds air
into the fuel tank if the vent lines become plugged.
Positive Crankcase Ventilation
All vehicles have a completely closed crankcase ventilation
system. Crankcase fumes are drawn into the intake manifold by manifold
vacuum. When intake manifold vacuum is low, the fumes are diverted
into the intake air duct ahead of the throttle body and turbocharger
(if equipped).
Secondary Air Injection System
When the engine is started and the catalytic converter is
cold, ambient air pumped into the catalytic converter will assist in
heating the converter to operating temperature. The secondary air
injection pump supplies ambient air to the catalytic converter
whenever the ECM determines it is needed, and is always supplied for
60 seconds. Power to the pump is switched by an ECM-controlled relay.
A solenoid valve controls output air from the pump.
SELF-DIAGNOSTIC SYSTEM
All models are equipped with an OBD-II self-diagnostic
system. When the system detects a malfunction, it sets a Diagnostic
Trouble Code (DTC) in the ECM memory and sends a signal to the
Malfunction Indicator Light (MIL). Fault diagnosis can be performed
using a generic scan tool connected to Data Link Connector (DLC)
located under left side of instrument panel.
MALFUNCTION INDICATOR LIGHT (MIL)
NOTE: MIL is also known as CHECK ENGINE light.
All vehicles are equipped with a MIL on the instrument panel
or trip computer. The light will come on when ignition is turned on
(bulb check), and when emission controls malfunction during normal
operation.
Perhaps another forum might be best.., wasn't sure, so will leave this up to the admin types...I hope this helps...
AIR INDUCTION SYSTEM
TURBOCHARGERS
On turbo models, a turbocharger and wastegate assembly are
mounted on the exhaust manifold. At idle and light throttle, the turbo
engine operates like a standard engine. When more power is required,
exhaust gases spin the impeller and turbine. Exhaust flow and
turbocharger RPM increase as engine RPM increases. As turbocharger RPM
increases, boost pressure also increases.
The wastegate is the system safety valve, preventing
excessive boost pressure which can cause engine damage. A signal from
the ECM energizes a solenoid which opens the wastegate to control
optimum boost pressure. In the event of control system failure, the
wastegate will open automatically to limit boost pressure.
Turbocharger operation requires a supply of clean oil. Engine
oil pressure provides lubrication to the system.
COMPUTERIZED ENGINE CONTROLS
Electronic components used in control systems are designed
to carry very low voltages. As little as a 30-volt charge
created by static electricity can cause a total or degrading
failure in the ECM or other electronic components containing
integrated circuits. Before servicing such components,
ground yourself and ground the work area to discharge stored
static electricity. Repeat grounding process periodically
during service procedure.
ENGINE CONTROL MODULE (ECM) (ECU)
On Motronic system, ECM is located under right side of
instrument panel. On Trionic system, ECM is located under right side
of instrument panel. For ECM pin and wire color identification, see
L - WIRING DIAGRAMS article. (which I also have if interested..)
ECM controls all engine functions: fuel injection, ignition
timing, idle speed, emission control, combustion analysis and selfdiagnostics.
On Motronic system, knock sensor functions are provided
by separate knock sensors. Trionic system has knock control but has no
external knock sensor.
NOTE: Components are grouped into 2 categories. The first category
is INPUT DEVICES, which are components that control or
produce voltage signals monitored by the control unit. The
second category is OUTPUT SIGNALS, which are components
controlled by the control unit.
INPUT DEVICES
Vehicles are equipped with different combinations of input
devices. Not all devices are used on all models. To determine the
input device usage on a specific model, see appropriate wiring diagram
in L - WIRING DIAGRAMS article. The available input signals include:
1. A/C Switch
When A/C is on, switch sends a signal to the fuel injection
ECM. The ECM sends a signal to the Idle Air Control (IAC) valve to
increase idle speed to compensate for increased load.
2. Coolant Temperature Sensor (CTS)
The CTS is located on the intake manifold flange. It
transmits an engine temperature signal to the fuel injection ECM. If
the ECM fails to receive this signal, it defaults to an assumed engine
temperature of 113
3. Knock Sensor (Motronic System)
This sensor is located in the engine block, below the intake
manifold. When knocking occurs, it sends a signal to the ignition and
APC ECMs. V6 applications require 2 sensors, one in each exhaust
manifold.
4. Gear Selector Switch
A/T models are equipped with a switch that signals the fuel
injection ECM whenever the transmission is in a range other than Park
or Neutral. The ECM signals the Automatic Idle Control (AIC) valve to
increase idle speed.
5. Heated Oxygen Sensor (HO2S)
This sensor measures quantity of free oxygen in the exhaust
gas. The ECM uses a signal from this sensor to adjust fuel mixture.
This sensor is located in the exhaust manifold and after TWC. The
electric heating element provides improved cold engine driveability.
6. Intake Air Temperature (IAT) Sensor
This sensor is used together with a MAP sensor to provide air
density information to the ECM. IAT is located on the intake air duct
leading to the throttle body.
7. Manifold Absolute Pressure (MAP) Sensor
This sensor is used together with the IAT sensor to provide
air density information to the ECM on some models. It is located on
firewall, toward the right side.
8. Mass Airflow (MAF) Sensor
The MAF sensor is located between the air cleaner and
throttle body. Sensor contains a ceramic plate which is heated
electrically to 356
9. Throttle Position (TP) Sensor
This sensor is located on the throttle body. It transmits
throttle position to the ECM.
Vehicle Speed Sensor (VSS)
On Motronic system, speedometer sends a speed signal to ECM.
On Trionic system, ABS control module sends a speed signal to ECM.
OUTPUT SIGNALS
NOTE: Vehicles are equipped with different combinations of
computer-controlled components. Not all components listed
below are used on every vehicle. For theory and operation on
each output component, refer to the system indicated after
component.
Idle Air Control (IAC) Valve
Canister Purge Solenoid
CHECK ENGINE Light
Fuel Pump Relay
Fuel Injectors
Idle-Up Solenoid
Ignition Coil(s)
Heated Oxygen Sensor
Secondary Air Injection Pump
Self-Diagnostics
Wastegate Solenoid
FUEL SYSTEM
FUEL DELIVERY
The fuel system consists of a fuel tank, fuel pump, fuel
lines, filter and a fuel pressure regulator. Fuel is supplied to each
injector at a constant pressure.
Fuel Pressure Regulator
Fuel pressure regulator, located on fuel rail, maintains
constant fuel pressure at fuel injectors. Excess fuel by-passes
injectors and returns to fuel tank.
Fuel Pump
Fuel pump is located in fuel tank. Fuel is strained through a
mesh screen before entering the pump. A check valve, located on outlet
side of pump, maintains pressure within the fuel system when engine is
off.
Fuel Pump Relay
Fuel pump relay supplies power to fuel pump. It is controlled
by the ECM.
FUEL CONTROL
ECM
ECM processes pulses from the crankshaft position sensor to
determine basic fuel injection timing. It also processes signals from
other sensors for calculating pulse duration to control fuel mixture.
Fuel Injectors
Fuel injectors, located in the intake manifold, spray
atomized fuel directly toward associated intake valves. All injectors
are supplied with fuel from a common fuel manifold. A signal from the
ECM controls injection pulse duration.
Heated Oxygen Sensor
The ECM sends a signal to a heating element in the oxygen
sensor. The function of the heating element is to more quickly bring
the sensing element to operating temperature.
IDLE SPEED
Idle Air Control (IAC) Valve
The IAC valve consists of an air control valve and integral
solenoid. This system provides a more stable idle speed during warm
and cold engine operation. The ECM sends a signal to the IAC valve to
control the amount of air by-passing the throttle valve.
IGNITION SYSTEM
MOTRONIC IGNITION SYSTEM
Motronic 4.1 engine control system used on 2.3L vehicles is a
conventional inductive ignition system with ignition coil and
distributor. On all other Motronic engine control system equipped
vehicles, ignition system is an inductive distributorless ignition
systems incorporating an ignition coil module.
TRIONIC IGNITION SYSTEM
The Trionic system is a distributorless capacitive discharge
type. Components include an ignition cartridge, Hall Effect sensor and
knock sensor. Each spark plug has a separate coil. Energy for the
spark is stored in a capacitor and discharged through the ignition
coil upon a signal from the ECM.
When ignition is switched on, both main relay and fuel pump
relay operate for a few seconds. As soon as ECM senses that crankshaft
has begun to rotate, coolant temperature dependent fuel injection
takes place through injectors simultaneously. This enables short
starting times to be achieved. If engine is started and shortly
afterward switched off again, a fresh pre-injection sequence will be
obtained if 45 seconds is allowed to pass with ignition switched off.
EMISSION SYSTEMS
Pulsed Secondary Air Injection
The pulse air injection system sends air to the exhaust
manifold to reduce exhaust emissions (HC and CO). Components of the
system include check valves, air injection manifolds, a nozzle by each
exhaust valve and an air supply hose from the air cleaner. Filtered
air from the air cleaner flows through the pulse air valves by means
of exhaust manifold pressure variation. Check valves prevent exhaust
gases from flowing back into the air cleaner.
Three-Way Catalytic Converter
All vehicles are equipped with a 3-way catalytic converter.
This device frees oxygen from oxides of nitrogen and oxidizes
hydrocarbons and carbon monoxide.
Fuel Evaporative System
Fumes from the fuel tank are stored in a charcoal canister
when the vehicle is not running. When the engine is started, intake
manifold vacuum purges these fumes through a canister purge solenoid,
upon a signal from the ECM. The canister is located in the left front
of the engine compartment.
A rollover valve in the fuel evaporation line closes if the
vehicle rolls over. It is located in the evaporation line, above the
fuel tank. A vacuum relief valve in the fuel filler cap bleeds air
into the fuel tank if the vent lines become plugged.
Positive Crankcase Ventilation
All vehicles have a completely closed crankcase ventilation
system. Crankcase fumes are drawn into the intake manifold by manifold
vacuum. When intake manifold vacuum is low, the fumes are diverted
into the intake air duct ahead of the throttle body and turbocharger
(if equipped).
Secondary Air Injection System
When the engine is started and the catalytic converter is
cold, ambient air pumped into the catalytic converter will assist in
heating the converter to operating temperature. The secondary air
injection pump supplies ambient air to the catalytic converter
whenever the ECM determines it is needed, and is always supplied for
60 seconds. Power to the pump is switched by an ECM-controlled relay.
A solenoid valve controls output air from the pump.
SELF-DIAGNOSTIC SYSTEM
All models are equipped with an OBD-II self-diagnostic
system. When the system detects a malfunction, it sets a Diagnostic
Trouble Code (DTC) in the ECM memory and sends a signal to the
Malfunction Indicator Light (MIL). Fault diagnosis can be performed
using a generic scan tool connected to Data Link Connector (DLC)
located under left side of instrument panel.
MALFUNCTION INDICATOR LIGHT (MIL)
NOTE: MIL is also known as CHECK ENGINE light.
All vehicles are equipped with a MIL on the instrument panel
or trip computer. The light will come on when ignition is turned on
(bulb check), and when emission controls malfunction during normal
operation.
