Outputs

Fig. 22 Power Distribution Center (PDC):

AIR CONDITIONING CLUTCH RELAY-PCM OUTPUT
The PCM controls the air conditioning clutch relay ground circuit. Buss bars in the Power Distribution Center (PDC) supply voltage to the solenoid side and power side of the relay. When the PCM receives an air conditioning input, it grounds the A/C compressor clutch relay and the radiator fan relay.

When the PCM senses low idle speeds or wide open throttle through the throttle position sensor, it removes the ground for the A/C compressor clutch relay. When the relay de-energizes, the contacts open preventing air conditioning clutch engagement. Also, if the PCM senses a part throttle launch condition, it disables the A/C compressor clutch for several seconds.

The air conditioning clutch relay is located in the PDC (Fig. 22). The inside top of the PDC cover has a label showing relay and fuse location.

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 20 amp fuse between the buss bar in the PDC and the relay. The fuse also protects the power circuit for the fuel pump relay and pump. The fuse is located in the PDC. Refer to Diagrams for circuit information.

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 02 Heater Monitor test is being run. 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.

The ASD relay is located in the PDC (Fig. 22). The inside top of the PDC cover has a label showing relay and fuse location.

CHARGING SYSTEM INDICATOR LAMP-PCM OUTPUT
The PCM turns the instrument panel Charging System Lamp on.

FUEL PUMP RELAY-PCM OUTPUT
The fuel pump relay supplies battery voltage to the fuel pump. A buss bar in the Power Distribution Center (PDC) supplies voltage to the solenoid side and contact side of the relay. The fuel pump relay power circuit contains a 20 amp fuse between the buss bar in the PDC and the relay. The fuse also protects the power circuit for the Automatic Shutdown (ASD) relay. The fuse is located in the PDC. Refer to Diagrams for circuit information.

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. The inside top of the PDC cover has a label showing relay and fuse location.

DUTY CYCLE EVAP 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 powertrain control module 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 engine enters closed loop operation after it reaches a specified temperature and the programmed time delay ends. During closed loop operation, the PCM energizes and de-energizes the solenoid 5 to 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 is energized.

Fig. 23 Duty Cycle EVAP Purge Solenoid:

The solenoid attaches to a bracket near the front engine mount (Fig. 23). To operate correctly, the solenoid must be installed with the electrical connector on top.

Electric EGR Backpressure Transducer -- Typical:

ELECTRIC EGR TRANSDUCER-PCM OUTPUT
The Electric EGR Transducer contains an electrically operated solenoid and a back-pressure controlled vacuum transducer (Fig. 24). The PCM operates the solenoid based on inputs from the multi- port fuel injection system. The transducer and EGR valve are serviced as an assembly

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 vacuum 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 the vacuum signal applied to the EGR valve. Varying the strength of the vacuum signal changes the amount of EGR supplied to the engine. This provides the correct amount of exhaust gas recirculation for different operating conditions.

Fig. 24 Electric EGR Backpressure Transducer-Typical:

The transducer and EGR valve mount to the rear of the cylinder head (Fig. 24).

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

Fig. 25 Idle Air Control Motor Air Bypass Passage -- Typical:

IDLE AIR CONTROL MOTOR-PCM OUTPUT
The Idle Air Control (IAC) motor is mounted on the throttle body The PCM operates the idle air control motor (Fig. 25). The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes.

The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. 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 IAC 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, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).

Fig. 26 Data Link Connector:

DATA LINK CONNECTOR
The data link connector (diagnostic connector) links the DRB or scan tool with the powertrain control module (PCM). The data link connector is located inside the vehicle, under the instrument panel, left of the steering column (Fig. 26).

Fig. 27 Fuel Injector:

FUEL INJECTORS-PCM OUTPUT
The 2.0L engine uses electronically operated top feed fuel injectors (Fig. 27). The Automatic Shutdown (ASD) relay supplies battery voltage to the fuel injectors. The PCM controls the ground path for each injector in sequence. By switching the ground paths on and off, the PCM fine-tunes injector pulse width. Injector pulse width refers to the amount of time an injector operates.

The PCM determines injector synchronization from the camshaft position sensor and crankshaft position sensor inputs. The PCM grounds the ASD and fuel pump relays after receiving the camshaft position sensor and crankshaft position sensor inputs.

The PCM energizes the injectors in a sequential order during all engine operating conditions except start-up. For the first injector pulse width during start-up, all injectors are energized at the same time. Once the PCM determines crankshaft position, it begins energizing the injectors in sequence.

Fig. 28 Ignition Coil Pack-SOHC:

IGNITION COIL-PCM OUTPUT
The coil assembly consists of 2 coils molded together. The coil assembly is mounted over the valve cover (Fig. 28). 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. Coil number one fires cylinders 1 and 4. Coil number two fires cylinders 2 and 3. The PCM determines which of the coils to charge and fire at the correct time.

The Auto 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 Auto Shutdown (ASD) Relay-PCM Output in this section for relay operation.

MALFUNCTION INDICATOR (CHECK ENGINE) LAMP-PCM OUTPUT
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).

The MIL can also display diagnostic trouble codes. Cycle the ignition switch on, off, on, off, on, within 5 seconds and any diagnostic trouble codes stored in the PCM will be displayed.


SCI RECEIVE-PCM OUTPUT
SCI Receive is the serial data communication receive circuit for the DRB scan tool. The Powertrain Control Module (PCM) receives data from the DRB through the SCI Receive circuit.

SPEED CONTROL SERVOS-PCM OUTPUT
The PCM controls the speed control vacuum servo. The PCM supplies power, through the brake switch, to the servo. Based on the speed control switch inputs to the PCM and the speed control strategy, the PCM provides ground to the servo vacuum or vent circuit as required. When the PCM supplies a ground to the servo vacuum circuit, the speed control system opens the throttle plate to obtain or maintain the selected road speed. When the PCM supplies a ground to the servo vent circuit, the speed control system releases the throttle plate.

TACHOMETER-PCM OUTPUT
The PCM operates the tachometer on the instrument panel. The PCM calculates engine RPM from the crankshaft position sensor input.

Fig. 30 Torque Convertor Clutch Solenoid:

TORQUE CONVERTOR CLUTCH SOLENOID-PCM OUTPUT
Three-speed automatic transaxles use a torque converter clutch solenoid. The PCM controls the engagement of the torque converter clutch through the solenoid (Fig. 30). The torque converter clutch is engaged up only in direct drive mode.