Outputs

AIR CONDITIONING (A/C) CLUTCH RELAY-PCM OUTPUT
The PCM operates the air conditioning clutch relay ground circuit, The radiator fan control module supplies battery power to the solenoid side of the relay. The air conditioning clutch relay will not energize unless the radiator fan control module energizes. The radiator control module energizes when the air conditioning or defrost switch is put in the ON position and the low pressure switch, combination valve, and high pressure switch close.

With the engine operating, the PCM cycles the air conditioning clutch on and off when the A/C switch closes with the blower motor switch in the On position. When the PCM senses low idle speeds or wide-open-throttle through the throttle position sensor, it de-energizes the A/C clutch relay. The relay contacts open, preventing air conditioning clutch engagement.

The air conditioning clutch relay is located in the Power Distribution Center (PDC). The PDC is located in the engine compartment next to the battery. A label affixed to the underside of the PDC cover identifies the relays and fuses in the PDC.

GENERATOR FIELD-PCM OUTPUT OPERATION
The PCM regulates the charging system voltage within a range of 12.9 to 15.0 volts.

AUTOMATIC SHUTDOWN RELAY-PCM OUTPUT
The Automatic Shutdown (ASD) relay supplies battery voltage to the fuel injectors, electronic ignition coil and the heating elements in the oxygen sensors.

A buss bar in the Power Distribution Center (PDC) supplies voltage to the solenoid side and contact side of the relay. The ASD relay power circuit contains a 25 amp fuse between the buss bar in the PDC and the relay. The fuse is located in the PDC.

The PCM controls the relay by switching the ground path for the solenoid side of the relay on and off. The PCM turns the ground path off when the ignition switch is in the Off position unless the O2 Heater Monitor test is being run. Refer to On-Board Diagnostics. When the ignition switch is in the On or Crank position, the PCM monitors the crankshaft position sensor and camshaft position sensor signals to determine engine speed and ignition timing (coil dwell). If the PCM does not receive the crankshaft position sensor and camshaft position sensor signals when the ignition switch is in the Run position, it will de-energize the ASD relay.

Power Distribution Center:

The ASD relay is located in the PDC. A label affixed to the underside of the PDC cover identifies the relays and fuses in the PDC.

FUEL PUMP RELAY-PCM OUTPUT
The fuel pump relay supplies battery voltage to the fuel pump. The fuel pump relay power circuit contains a 9 amp fuse. The fuse is located in the PDC.

The PCM controls the fuel pump relay by switching the ground path for the solenoid side of the relay on and off. The PCM turns the ground path off when the ignition switch is in the Off position. When the ignition switch is in the On position, the PCM energizes the fuel pump. If the crankshaft position sensor does not detect engine rotation, the PCM de-energizes the relay after approximately one second.

The fuel pump relay is located in the PDC. A label affixed to the underside of the PDC cover identifies the relays and fuses in the PDC.

STARTER RELAY-PCM OUTPUT
Double Start Override is a feature that prevents the starter from operating if the engine is already running. This feature is accomplished with software only. There was no hardware added because of this feature. To incorporate the unique feature of Double Start Override, it was necessary to use the PCM (software) to control the starter circuit. To use the PCM it was necessary to separate the starter relay coil ground from the park neutral switch. The starter relay ground is now controlled through Pin 60 of the PCM. This allows the PCM to interrupt the ground circuit if other inputs tell it that the engine is turning. If the starter system is operating properly, it can be assumed that the override protection is also working.

IDLE AIR CONTROL MOTOR-PCM OUTPUT
The idle air control motor is mounted on the throttle body. The PCM operates the idle air control motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load or ambient conditions.

The throttle body has an air bypass passage that provides air for the engine at idle (the throttle blade is closed). The idle air control motor pintle protrudes into the air bypass passage and regulates air flow through it.

The PCM adjusts engine idle speed by moving the idle air control motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, and various switch operations (brake, park/neutral, air conditioning). Deceleration die out is also prevented by increasing airflow when the throttle is closed quickly after a driving (speed) condition.

DUTY CYCLE EVAP CANISTER PURGE SOLENOID-PCM OUTPUT
The duty cycle EVAP purge solenoid regulates the rate of vapor flow from the EVAP canister to the throttle body. The PCM operates the solenoid.

During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.

The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the PCM energizes and de-energizes the solenoid 5 or 10 times per second, depending upon operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time the solenoid energizes.

Duty Cycle EVAP Purge Solenoid:

A rubber boot covers the duty cycle EVAP purge solenoid. The solenoid attaches to a bracket mounted to the right engine mount. The top of the solenoid has the word TOP on it. The solenoid will not operate properly unless it is installed correctly.

PROPORTIONAL PURGE SOLENOID

Proportional Purge Solenoid:

All vehicles use a proportional purge solenoid. The solenoid regulates the rate of vapor flow from the EVAP canister to the throttle body. The PCM operates the solenoid.

During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged.

The proportional purge solenoid operates at a frequency of 200 hz and is controlled by an engine controller circuit that senses the current being applied to the proportional purge solenoid and then adjusts that current to achieve the desired purge flow. The proportional purge solenoid controls the purge rate of fuel vapors from the vapor canister and fuel tank to the engine intake manifold.

ELECTRONIC EGR TRANSDUCER SOLENOID-PCM OUTPUT

EGR Solenoid:

The electronic EGR transducer contains an electrically operated solenoid and a back-pressure transducer. The PCM operates the solenoid. The PCM determines when to energize the solenoid. Exhaust system back-pressure controls the transducer.

When the PCM energizes the solenoid, vacuum does not reach the transducer. Vacuum flows to the transducer when the PCM de-energizes the solenoid.

When exhaust system back-pressure becomes high enough, it fully closes a bleed valve in the transducer. When the PCM de-energizes the solenoid and back-pressure closes the transducer bleed valve, vacuum flows through the transducer to operate the EGR valve.

De-energizing the solenoid, but not fully closing the transducer bleed hole (because of low back-pressure), varies the strength of vacuum applied to the EGR valve. Varying the strength of the vacuum changes the amount of EGR supplied to the engine. This provides the correct amount of exhaust gas recirculation for different operating conditions.

Data Link Connector:

DATA LINK CONNECTOR-PCM OUTPUT
The data link connector provides the technician with the means to connect the DRB scan tool to diagnosis the vehicle. The connector is located under the dash.

AUTOMATIC TRANSAXLE CONTROL MODULE-PCM OUTPUT
The electronic automatic transaxle control module and the PCM supply information to each other through the CCD Bus. The information includes engine speed and vehicle load. The PCM uses the information when adjusting the fuel and ignition strategy.

Fuel Injector:

FUEL INJECTORS-PCM OUTPUT
The fuel injectors are 12 ohm electrical solenoids. The injector contains a pintle that closes off an orifice at the nozzle end. When electric current is supplied to the injector, the armature and needle move a short distance against a spring, allowing fuel to flow out the orifice. Because the fuel is under high pressure, a fine spray is developed in the shape of a hollow cone. The spraying action atomizes the fuel, adding it to the air entering the combustion chamber. The injectors are positioned in the intake manifold.

Fuel Injector Location-Typical:

The injectors are positioned in the intake manifold with the nozzle ends directly above the intake valve port.

The fuel injectors are operated by the PCM. They are energized in a sequential order during all engine operating conditions except start up. The PCM initially energizes all injectors at the same time. Once PCM determines crankshaft position, it begins energizing the injectors in sequence.

The Automatic Shutdown (ASD) relay supplies battery voltage to the injectors. The PCM provides the ground path for the injectors. By switching the ground path on and off, the PCM adjusts injector pulse width. Pulse width is the amount of time the injector is energized. The PCM adjusts injector pulse width based on inputs it receives.

IGNITION COIL-PCM OUTPUT

Ignition Coil:

The coil assembly consists of independent coils molded together. The coil assembly is mounted on the intake manifold. High tension leads route to each cylinder from the coil. The coil fires two spark plugs every power stroke. One plug is the cylinder under compression, the other cylinder fires on the exhaust stroke. The PCM determines which of the coils to charge and fire at the correct time.

The Automatic Shutdown (ASD) relay provides battery voltage to the ignition coil. The PCM provides a ground contact (circuit) for energizing the coil, When the PCM breaks the contact, the energy in the coil primary transfers to the secondary causing the spark. The PCM Will de-energize the ASD relay if it does not receive the crankshaft position sensor and camshaft position sensor inputs. Refer to Automatic Shutdown (ASD) Relay-PCM Output for relay operation.

TORQUE CONVERTER CLUTCH SOLENOID-PCM OUTPUT
Three-speed automatic transaxies use a torque converter clutch solenoid. The PCM controls the engagement of the torque converter clutch through the solenoid. The torque converter clutch is engaged only in direct drive mode.

MALFUNCTION INDICATOR (CHECK ENGINE) LAMP-PCM OUTPUT
OPERATION
The PCM supplies the malfunction indicator (check engine) lamp on/off signal to the instrument panel through the CCD Bus. The CCD Bus is a communications port. Various modules use the CCD Bus to exchange information.

The Check Engine lamp comes on each time the ignition key is turned ON and stays on for 3 seconds as a bulb test.

The Malfunction Indicator Lamp (MIL) stays on continuously, when the PCM has entered a Limp-In mode or identified a failed emission component. During Limp-in Mode, the PCM attempts to keep the system operational. The MIL signals the need for immediate service. In limp-in mode, the PCM compensates for the failure of certain components that send incorrect signals. The PCM substitutes for the incorrect signals with inputs from other sensors.

If the PCM detects active engine misfire severe enough to cause catalyst damage, it flashes the MIL.

At the same time the PCM also sets a Diagnostic Trouble Code (DTC). For signals that can trigger the MIL (Check Engine Lamp) refer to the On-Board Diagnostics Chart.

SOLID STATE FAN RELAY-PCM OUTPUT
The radiator fan runs at a variable speed depending on coolant temperature and A/C system pressure. The radiator fan circuit contains a Solid State Fan Relay (SSFR).

A 5 volt signal is supplied to the SSFR. The PCM provides a pulsed ground for the SSFR. Depending upon the amount of pulse on time, the SSFR puts out a proportional voltage to the fan motor at the lower speed. For instance, if the on time is 30 percent, then the voltage to the fan motor will be 3.6 volts.

When engine coolant reaches approximately 102° C (215° F) the PCM grounds the SSFR relay. If engine coolant reaches 207° C (225° F) the PCM grounds the high speed ground relay and high speed fan relay. If the fan operates at high speed, the PCM de-energizes the high speed relay and high speed ground relay when coolant temperature drops to approximately 101° C (214° F). When coolant temperature drops to 101° C (214° F) the fan operates at low speed. The PCM de-energizes the low speed relay when coolant temperature drops to approximately 93° C (199° F).

Also, when the air conditioning pressure switch closes, the fan operates at high speed. The air conditioning switch closes at 285 psi ± 10 psi. When air conditioning pressure drops approximately 40 psi, the pressure switch opens and the fan operates at low speed.

Fan Control Module:

The SSFR relay is located on the left front inner frame just behind the radiator.

SPEED CONTROL SOLENOIDS-PCM OUTPUT
The speed control vacuum and vent solenoids are operated by the PCM. When the PCM supplies a ground to the vacuum and vent solenoids, the speed control system opens the throttle plate. When the PCM removes the ground from the vacuum and vent solenoids, the throttle blade closes. The PCM balances the two solenoids to maintain the set speed.

TACHOMETER-PCM OUTPUT
The PCM supplies engine RPM to the instrument panel tachometer through the CCD Bus. The CCD Bus is a communications port. Various modules use the CCD Bus to exchange information.

Throttle Body - 2.4L:

Throttle Body - 3.0L:

Throttle Body - 3.3/3.8L:

THROTTLE BODY
On all engine assemblies the throttle body's are located on the left side of the intake manifold plenum. The throttle body houses the throttle position sensor and the idle air control motor. Air flow through the throttle body is controlled by a cable operated throttle blade located in the base of the throttle body.