Outputs

Fig. 22 Duty Cycle EVAP Purge Solenoid:

AIR CONDITIONING COMPRESSOR CLUTCH RELAY-PCM OUTPUT
The powertrain control module (PCM) operates the air conditioning clutch relay ground circuit. The battery supplies power to the solenoid side of the relay. The PCM grounds the relay when the operator puts the A/C or defrost switch in the ON position and it receives an acceptable input from the A/C pressure transducer. If the A/C pressure transducer input indicates high side pressure is too high or too low, the PCM will not ground the A/C compressor clutch relay.

With the engine operating, the PCM cycles the air conditioning clutch on and off during A/C operation. When the PCM senses low idle speeds or wide open throttle through the throttle position sensor, it de-energizes the A/C compressor clutch relay.

The A/C compressor clutch relay is located in the power distribution center (PDC) near the battery (Fig. 21). A decal on the inside of the PDC covers shows the locations of each relay and fuse contained in the PDC.

AUTOMATIC SHUT DOWN (ASD) AND FUEL PUMP RELAYS-PCM OUTPUT
The PCM operates the automatic shut down (ASD) relay and fuel pump relay through one ground path. The PCM operates them by switching the ground path for the solenoid side of the relays on and off. Both relays turn on and off at the same time.

The ASD relay connects battery voltage to the fuel injectors and ignition coil. The fuel pump relay connects battery voltage to the fuel pump.

The PCM turns the ground path off when the ignition switch is in the Off position. Both relays are off. 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 a crankshaft position sensor signal and camshaft position sensor signal when the ignition switch is in the Run position. it de-energizes both relays. When the relays are de-energized, battery voltage is not supplied to the fuel injectors, ignition coil and fuel pump.

The ASD relay and fuel pump relay are located in the power distribution center (PDC) near the battery. A decal on the inside of the PDC covers shows the locitions of each relay and fuse contained in the PDC.

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.

The EVAP purge solenoid and bracket attach to the right inner fender well next to the dash panel (Fig. 22). The top of the solenoid has the word TOP on it. The solenoid will not operate unless it is installed correctly. If the vehicle has a 3.5L engine, the EVAP purge solenoid shares a bracket with the MTV solenoid.

Fig. 23 EGR Solenoid:

ELECTRONIC EGR TRANSDUCER SOLENOID-PCM OUTPUT
The electronic EGR transducer (EET) contains an electrically operated solenoid and a back-pressure transducer (Fig. 23). The powertrain control module (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.

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:

Fig. 26 Idle Air Passage:

IDLE AIR CONTROL MOTOR-PCM OUTPUT
The idle air control motor attaches to the throttle body (Fig. 25). 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 (Fig. 26).

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 effecting idle speed include the throttle position sensor road speed (from transmission control module), coolant temperature sensor, battery voltage and battery temperature. Also various switch operations (brake, park/neutral, air conditioning) effect idle speed. The PCM prevents deceleration die out by increasing airflow when the throttle closes quickly.

Fig. 29 Data Link Connector:

DATA LINK CONNECTOR-PCM OUTPUT
The data link connector ([1][2]diagnostic connector) links the DRB scan tool with the powertrain control module (PCM). The data link connector is located inside the vehicle, below instrument panel next to the center column (Fig. 29).

Fig. 31 Fuel Injector:

FUEL INJECTORS-PCM OUTPUT
Fuel from the rail enters the top of the injectors (Fig. 31).

The automatic shut down (ASD) relay supplies battery voltage to the injectors. The PCM controls the ground path for each injector in sequence. By switching the ground paths on and off, the PCM time-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. During start-up, when the coolant temperature is below 15°C (60°F), all injectors are energized at the same time. Above 150°C, the PCM energizes the injectors in sequence. Once the PCM determines crankshaft position, it begins energizing the injectors in sequence.

Fig. 32 Ignition Coil Pack:

IGNITION COIL-PCM OUTPUT
The coil assembly consists of 3 coil molded together (Fig. 32). The coil assembly is connected on the intake manifold. High tension leads rotate 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 shut down (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 sensor and camshaft sensor inputs.

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.

RADIATOR FAN RELAYS-PCM OUTPUT
The cooling system uses two fans. Both fans operate at two different speeds, low and high. Depending on engine coolant temperature and A/C system high side pressure, the both fans operate at either low or high. The PCM controls radiator speed by grounding the coil side of either the low speed fan relay or the high speed fan relay The ignition switch supplies voltage to the coil sides of the relay. When the PCM grounds the coil side of the relay, the contacts close and the battery supplies power to the fans.

The low speed and high speed fan relays are located in the power distribution center (PDC) near the battery A decal on the inside of the PDC covers shows the locations of each relay and fuse contained in the PDC.

FAN OPERATION-PCM OUTPUT
With the A/C off, the PCM energizes the low speed fan when engine coolant temperature reaches approximately 99°C (211°F). Also with the A/C off the PCM de-energizes the low speed fan when coolant temperature drops to approximately 93°C (99°F).

The PCM energizes the high speed fan when engine coolant temperature reaches approximately 110°C (230°F). The PCM de-energizes the high speed fan and energizes the low speed fan when coolant temperature drops to approximately 104°C (219°F).

When the PCM receives an input from the A/C pressure transducer indicating high side pressure is approximately 1448 kPa (210 PSI), it energizes the low speed fan. The PCM de-energizes the low speed when the high side pressure drops to 861 kPa (125 PSI if engine coolant temperature is below approximately 93°C (200°F).

When the PCM receives an input from the AC pressure transducer indicating high side pressure is approximately 1724 kPa (250 PSI), it energizes the high speed fan. The PCM de-energizes the high speed fan and energizes the low speed when the high side pressure drops to 1586 kPa (230 PSI).

SPEED CONTROL RELAY-PCM OUTPUT
When the operator engages the speed control PCM receives a input from the speed control On switch. In response to the input, the PCM grounds the coil side of the speed control relay. The ignition switch supplies power to the coil and contact sides of the relay When energized, the speed control relay supplies battery voltage to the speed control vacuum and vent servos.

SPEED CONTROL SERVOS-PCM OUTPUT
The PCM operates the speed control vacuum and vent servos. The PCM supplies a ground for both servos. The speed control relay supplies. also operated by the PCM, supplies battery voltage to the servos When the PCM supplies a ground to the vacuum servo, the speed control system opens the throttle plate to obtain or maintain the selected road speed When the PCM supplies a ground to the vent servo. the speed control system releases the throttle plate. The PCM balances the two servos to maintain the set speed.

TACHOMETER-PCM OUTPUT
The tachometer receives its information across the CCD Bus from the Body Control Module (BCM). Information on engine RPM is transmitted from the Powertrain Control Module (PCM) across the CCD Bus to the BCM. The BCM calculates the position of the tachometer pointer based on the input from the PCM and adjusts the position of the gauge pointer to the necessary position. This signal is sent over the CCD Bus to the instrument cluster

5 VOLT SUPPLY-PCM OUTPUT
The PCM supplies 5 volts to the following sensors:
- A/C pressure transducer
- Engine coolant temperature sensor
- Manifold absolute pressure sensor
- Throttle position sensor

8-VOLT SUPPLY-PCM OUTPUT
The PCM supplies 8 volts to the crankshaft position sensor, camshaft position sensor