2.2l Efi Theory/operation — Dodge Aries I (1981-1989)

DESCRIPTION

The computerized engine control systems used on 2.2L fuel injected engines controls the fuel system, ignition system, and emission control system for proper engine operation. Throttle Body Injection is used on non-turbo models, while Multi-Point Fuel Injection is used on turbo models.

In order to control these systems, the computer monitors several engine and vehicle operating conditions. The engine conditions monitored include: manifold absolute pressure, throttle position, coolant temperature, charge temperature (turbo only), manifold air temperature, exhaust gas oxygen content, and vehicle distance/engine speed.

Vehicle conditions monitored include vehicle speed and the status (off or on) of several vehicle systems that affect engine load. These include the transmission neutral-safety, brake light and air conditioning clutch switches.

The engine control computer consists of 2 separate modules. The logic module processes all sensor inputs and controls all low power output devices. The logic module also controls the power module. The power module controls the injector(s), ignition coil, and auto shutdown relay.

Non-Turbo Computer, Input Sensors & Output Devices Schematic. Scheme 1

Scheme 1: Non-Turbo Computer, Input Sensors & Output Devices Schematic

Turbo Computer, Input Sensors & Output Devices Schematic. Scheme 2

Scheme 2: Turbo Computer, Input Sensors & Output Devices Schematic

The computerized engine control system consists of 6 sub-systems: computer, sensors and switches, fuel control, ignition, emission control, and air conditioning compressor cut-out.

COMPUTER

The computer is divided into 2 modules. The logic module contains the operating software and performs the calculations and adjustments necessary for engine operation. This half of the computer is located inside the passenger compartment behind the right front kick panel.

The logic module is a microprocessor based digital computer, with two 25-pin connectors. This module receives input signals from various switches, sensors, and other components. Using these signals, the microprocessor computes the fuel injector pulse width, spark advance, ignition coil dwell, automatic idle speed actuation, canister purge, and EGR control solenoid cycles, cooling fan and alternator.

The logic module also contains a diagnostic circuit to test input and output circuits. The diagnostic circuit will store information about any malfunctions as they occur for readout prior to service. Either the Chrysler Diagnostic Readout Box (DRB), Tool No. (C-4805) or the flashing Power Loss/Power Limit Lamp may be used in diagnosing and displaying trouble codes. However, the Power Loss Lamp is limited in its diagnosis.

The second part of the computer is the power module, with 10 pin and 12-pin connectors. The power module contains a voltage converter which maintains the power supply at 8 volts. The module controls the circuits for the fuel injector, the ignition system, and the automatic shutdown relay.

The power module is located in the engine compartment because the high current draw of the devices being controlled can cause electrical noise which must be isolated from the logic module. The power module is controlled by the logic module.

Logic Module, Connectors and MAP Sensor. Scheme 3

Scheme 3: Logic Module, Connectors and MAP Sensor

Automatic Shutdown Relay (ASD)

The ASD relay is controlled by the power module. When the power module senses a distributor signal during cranking, it grounds the ASD closing contacts. This completes the circuit for the electric fuel pump, power module, and ignition coil. If the distributor signal is lost for any reason, the ASD shuts off this circuit in less then one second, preventing fuel, spark, and engine operations.

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor is located in the passenger compartment, mounted on the logic module. The MAP sensor monitors manifold vacuum through a vacuum line from the throttle body to the sensor.

The sensor supplies the logic module with an electrical signal which keeps the module informed of manifold vacuum conditions and barometric pressure. This information is combined with data supplied by other sensors to determine correct air/fuel ratio.

Oxygen (O2) Sensor

The oxygen sensor is screwed into the top of the exhaust manifold, just ahead of the tail-pipe connection, so that it is exposed to exhaust gas flow. Its function is to monitor the oxygen content of the exhaust, and to supply the logic module with a voltage signal which is directly proportional to this content.

If the oxygen content of the exhaust is high (lean air/fuel mixture), the voltage signal from the sensor to the logic module is low. As oxygen content decreases (mixture becomes richer), the signal voltage increases.

In this manner, the logic module is kept constantly informed of air/fuel ratio. It can then alter fuel injector "on" time, in response to these signals, to obtain the best air/fuel ratio under any given condition.

Coolant Temperature Sensor (CTS)

The Coolant Temperature Sensor measures temperature of engine coolant. The coolant temperature sensor is mounted in the thermostat housing to monitor engine coolant (operating) temperature. It supplies the logic module with a voltage signal which varies with coolant temperature.

Information provided by this sensor allows the logic module to demand slightly richer air/fuel mixtures and higher idle speeds during cold engine operation.

Charge Temperature Sensor

The Charge Temperature Sensor (turbo only), measures the temperature of the incoming air/fuel mixture. The sensor, mounted in the intake manifold, supplies the logic module with information on the temperature of the incoming air/fuel mixture.

Lastly, if the coolant temperature switch should malfunction, information supplied by the charge temperature sensor (turbo only) is sufficient to determine engine operating temperature and engine warm-up cycles until the coolant temperature sensor can be repaired or replaced.

Throttle Position Sensor (TPS)

The TPS is a variable resistor which is operated by the movement of the throttle shaft. It is mounted on the throttle body and senses the angle of throttle blade opening.

A voltage signal is produced by the sensor which varies with this angle. This signal is transmitted to the logic module where it is used to adjust air/fuel ratio during acceleration, deceleration, idle, and wide open throttle conditions.

Engine Switches

Several switches provide operating information to the logic module. These include the idle, neutral safety, air conditioning clutch, and brake light switches. If one or more of these switches is sensed as being in the "on" position, the logic module signals the Automatic Idle Speed Motor (AIS) to increase idle speed to a specific RPM.

With the air conditioning on and the throttle blade above a specific angle, the wide open throttle cut-out relay prevents the air conditioning clutch from engaging until the throttle blade angle is reduced.

Fuel Pump

An electric, positive-displacement, roller vane type fuel pump is located in the fuel tank as an integral part of the fuel gauge sending unit. Shelby Turbo models use two fuel pumps, one inside the fuel tank and one outside. The fuel pump supplies fuel to the fuel regulator.

Power to the fuel pump is supplied by the power module via the Automatic Shut-Down (ASD) relay. The power module is supplied with an operating signal from the distributor. If this signal is not received, the ASD relay is not activated and power to the fuel pump is cut off.

Fuel Regulator

On non-turbo models, the fuel regulator supplies fuel to the fuel injector at a constant 36 psi (2.5 kg/cm 2 ) pressure. On turbo models, the regulator supplies fuel to the fuel rail and its four injectors at a constant 53 psi (3.7 kg/cm 2 ) pressure.

Fuel Injector

The fuel injector, an electrical solenoid, is mounted in the throttle body on non-turbo models so that fuel from the injector is directed into the incoming air stream. On turbo models, 4 injectors are mounted on a fuel rail, supplying the intake manifold with the proper fuel supply.

While power to the injector is supplied by the power module, it is controlled by indirect signal from the logic module, which actually determines when and how long the injector is open. When electric current is supplied to the injector, an integral armature and pintle valve move a short distance against a spring, opening a small orifice.

Fuel supplied to the injector is forced around the pintle valve and through this opening, resulting in a fine spray of fuel in the shape of a hollow cone. As a constant pressure drop is maintained across the injector (by the pressure regulator), the length of time that this opening is maintained (injector "on" time) determines the amount of fuel entering the engine and, therefore, the air/fuel ratio.

Cross-Sectional View of Fuel Injector 4 fuel injectors are used on turbo models. Scheme 4

Scheme 4: Cross-Sectional View of Fuel Injector 4 fuel injectors are used on turbo models.

Automatic Idle Speed Motor (AIS)

The AIS is mounted on the throttle body assembly and is controlled by electrical signal from the logic module. The logic module uses sensor input to determine optimum engine idle speed for any idle condition.

The AIS is then adjusted to allow a specific amount of air through an air by-pass on the back of the throttle body. This by-pass is enlarged or restricted, as an increase or decrease in engine idle speed is required to meet varying engine operating conditions.

This results in a change in air/fuel ratio, which alters the oxygen content of the exhaust gases as detected by the oxygen sensor. The logic module then changes the amount of fuel introduced into the intake charge to maintain an ideal air/fuel ratio.

IGNITION

The pick-up coil in the distributor feeds a signal to the power module and the logic module. Spark advance, dwell and timing are computed in the logic module. The logic module sends a signal back to the power module where the coil ground is switched off and on to create an ignition secondary pulse.

EMISSION CONTROL

Note. Both turbo and non-turbo systems use back pressure type EGR systems. A back pressure transducer measures amount of exhaust back pressure on the exhaust side of the GR valve and varies strength of the vacuum signal applied to the EGR valve. The transducer adjusts the EGR signal to provide programmed amounts of EGR under all conditions.

Exhaust Gas Recirculation Solenoid (Turbo)

On turbo models, EGR is controlled two ways. The logic module controls vacuum through the EGR solenoid, turning the vacuum circuit on and off. The transducer varies the strength of the vacuum signal applied to the EGR valve. When engine temperature is below 70°F (21°C), the logic module energizes the solenoid by completing the ground circuit. This closes the solenoid valve and prevents ported vacuum from reaching the EGR valve. When the predetermined temperature is reached, the logic module will break the ground circuit, which opens the valve allowing vacuum to reach the EGR valve. The solenoid valve is also closed, preventing EGR operation, during idle and wide open throttle operation.

Purge Solenoid

The purge solenoid operates in a manner similar to the EGR solenoid used on turbo models. When engine temperature is below 145°F (61°C), the logic module completes the ground circuit for the purge solenoid. This closes the solenoid valve, preventing vacuum from reaching the charcoal canister valve. When this temperature is reached, the logic module breaks the ground circuit, allowing vacuum to reach the canister purge valve so that fuel vapors may be purged from the canister.

A/C COMPRESSOR CUT-OUT

The air conditioning cut-out relay is wired in series with the cycling clutch switch and low pressure cut-out switch. This relay is normally closed during engine operation. When the logic module senses a wide open throttle condition through the throttle position sensor, it energizes the relay, opening the circuit and preventing compressor clutch engagement.

POWER LOSS/POWER LIMIT LAMP

This lamp comes on each time the ignition key is turned on and stays on for a few seconds as a bulb test. It also illuminates when incorrect signals or no signal is received from various sensors. It also is used to display some trouble codes, but does not have the capability of diagnosis provided by the Chrysler Diagnostic Readout Box (DRB), Tool No. (C-4805). See SYSTEM DIAGNOSIS.

WASTEGATE CONTROL SOLENOID

On turbo models, the logic module adjusts maximum boost to match changing engine conditions by varying the duty cycle of the wastegate solenoid.

BAROMETRIC READ SOLENOID

The barometric read solenoid is controlled by the logic module. Located in the MAP vacuum line, the solenoid measures barometric pressure at closed throttle, once per throttle closure, but no more often than once every 30 seconds and below a specified RPM. The information is used for boost control.

INDICATOR CODE DESCRIPTIONS

Indicator codes are 2-digit numbers that will tell you if certain sequences or conditions have occurred.

Code 88

This code implies the "start of diagnostic mode." If this code is not displayed first, trouble codes will be inaccurate.

Code 55

This is the "end of diagnostic mode." This code will always appear as the final code after all other trouble codes have been displayed.

Code 0

Indicates oxygen feedback system is lean with engine running.

Code 1

Indicates oxygen feedback system is rich with engine running.

Code 8 (Turbo Only)

Indicates detonation sensor system is detecting a knock.

Code 12

Problem with battery feed to logic module. Occurs when feed has been disconnected within last 20-40 engine starts.

ATM CODES

Actuation Test Mode (ATM) test codes are 2-digit numbers, appearing on the Diagnostic Readout Box (DRB), that identify various circuits that will be used during diagnostics. They are listed under applicable trouble codes.

TROUBLE CODE DESCRIPTIONS

The Chrysler Throttle Body and Multi-Point Fuel Injection systems are equipped with a self-diagnostic capability which stores certain "trouble codes" in the logic module when system malfunctions occur. These codes may be recalled to aid in system diagnosis. The following list presents these codes and the system malfunctions which they represent.

Code 11

Problem with distributor circuit. No distributor signal to logic module since restoration of battery voltage.

Code 13

Problem with MAP sensor pneumatic system. Appears if sensor vacuum level does not change between cranking and when engine starts.

Code 14

Problem with MAP sensor electrical system. MAP sensor signal outside of .02-4.9 volt range.

Code 15

Problem with Distance/Speed Sensor circuit. During 7-second period of deceleration from highway speeds with throttle closed, sensor indicates less than 2 MPH when vehicle is moving.

Code 16

Problem with loss of battery voltage sense. Occurs if sensing voltage drops below 4 volts or between 7.5-8.0 volts for more than 20 seconds.

Code 17 (Turbo Only)

Problem with detonation sensor circuit. Occurs when there is no knock signal above 5000 engine RPM for 3 seconds.

Code 21

Problem with O2 Sensor feedback circuit. Occurs if engine temperature is above 170°F (77°C), engine speed is above 2000 RPM, but O2 sensor stays rich or lean (no signal) for more than 22 seconds.

Code 22

Problem with Coolant Temperature Sensor circuit. Appears if coolant sensor voltage is below .51 volt when engine is warm or above 4.96 volts when engine is cold.

Code 23 (Turbo Only)

Problem with Charge Temperature Sensor circuit. Appears if the charge temperature sensor voltage is below .06 volt or above 4.98 volts.

Code 24

Problem with TPS circuit. Appears if the sensor signal is either below .16 volt or above 4.7 volts.

Code 25

Problem with AIS control circuit. Appears if proper voltage from AIS system is not present. An open harness or motor will not activate this code. ATM code 03.

Code 26 (Non-Turbo Only)

During cranking, indicates that peak injector current level has not been reached. ATM code 02.

Code 26 (Turbo Only)

Problem with injectors 1 and 2 firing improperly during cranking. ATM code 02.

Code 27 (Non-Turbo Only)

Problem with fuel control circuit in the logic module, when fuel control interface fails to switch properly.

Code 27 (Turbo Only)

Problem with injectors 3 and 4 firing improperly during cranking. ATM code 02.

Code 31

Problem with Canister Purge Solenoid circuit. Appears if solenoid does not turn on and off when it should. ATM code 07.

Code 32

Problem with Power Loss Lamp circuit. Appears if the lamp does not turn on and off when it should.

Code 33

Problem with A/C cut-out relay driver circuit. Occurs when relay does not turn on and off when it should. ATM code 05.

Code 34 (Non-Turbo Only)

Problem with spare driver circuit.

Code 34 (Turbo Only)

Problem with EGR solenoid circuit. Occurs if solenoid does not turn on and off when it should. ATM code 08.

Code 35

Problem in the radiator fan relay circuit. Appears if relay does not turn on and off when it should. ATM code 04.

Code 36 (Non-Turbo Only)

Problem with spare driver circuit.

Code 36 (Turbo Only)

Problem with wastegate control solenoid circuit. Occurs if solenoid does not turn on and off when it should. ATM code 09.

Code 37 (Non-Turbo Only)

Problem with shift indicator lamp circuit (Man. Trans. only). Occurs when lamp does not turn on and off when it should.

Code 37 (Turbo Only)

Problem with the barometric read solenoid circuit. Appears when solenoid does not turn on and off when it should. ATM code 10.

Code 41

Problem with charging system. Appears if field control fails to switch properly.

Code 42

Problem in the ASD relay circuit. Appears if control voltage of the relay pull-in coil in the power module is not correct. Relay does not turn on and off when it should. ATM code 06.

Code 43

Problem in the spark control interface circuit. Appears if the spark control interface fails to switch properly. ATM code 01.

Code 44 (Non-Turbo Only)

Problem with battery temperature sensing voltage being out of .04-4.90 volt range.

Code 45 (Turbo Only)

Problem in the over boost shut-off circuit. This code appears if MAP sensor signal exceeds a predetermined amount of boost indication.

Code 46

Problem is battery voltage sensing is too high. Appears if battery sense voltage is more than 1 volt above the desired control voltage for more than 20 seconds.

Code 47

Problem is battery sensing voltage is too low. Appears if battery sensing voltage is more than 1 volt below the desired control voltage for more than 20 seconds. Occurs with engine temperature above 160°F and speed above 1500 RPM.

Code 51

Problem with oxygen feedback system being latched lean (stays lean more than 2 minutes).

Codes 52

Problem with oxygen feedback system being latched rich. (stays lean more than 2 minutes).

Code 53

Problem with an internal logic module failure.

Code 54 (Turbo Only)

Problem in the synchronization pick-up circuit. Appears, if at start/run transfer speed, the distributor pick-up signal is present, but the synchronization pick-up signal is missing at the logic module.