Outputs

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

Fig 23 Power Distribution Center:

AUTOMATIC SHUTDOWN RELAY -- 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.

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.

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 and fuel pump relay are located in the power distribution center (PDC) near the battery (Fig. 23). The inside top of the PDC cover has a label showing relay and fuse location.

Fig 24 Duty Cycle EVAP Purge Solenoid:

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 solenoid attaches to a bracket near the front engine mount (Fig. 24). To operate correctly, the solenoid must be installed with the electrical connector on top.

Fig 25 Electronic EGR Transducer:

ELECTRIC EGR TRANSDUCER -- PCM OUTPUT
The Electric EGR Transducer contains an electrically operated solenoid and a back-pressure controlled vacuum transducer (Fig. 25). The PCM operates the solenoid based on inputs from the multiport fuel injection system. The solenoid/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 26 Electric EGR Transducer:

The solenoid/transducer and EGR valve mount to the rear of the cylinder head (Fig. 26).

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

Fig 28 Idle Air Control Motor Air Bypass Passage:

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. 28). 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 30 Data Link Connector:

DATA LINK CONNECTOR
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, under the instrument panel, at the driver's kick panel (Fig. 30).

Fig 31 Fuel Injector:

FUEL INJECTORS -- PCM OUTPUT
This engine uses electrically operated top feed fuel injectors (Fig. 31). 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 33 Ignition Coil:

IGNITION COIL -- PCM OUTPUT
The coil assembly consists of independent coils molded together (Fig. 33). 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 in this article 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).

For signals that can trigger the MIL (Check Engine Lamp) refer to On-Board Diagnostics. Testing and Inspection

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. Refer to Trouble Code Descriptions. Testing and Inspection

RADIATOR FAN RELAYS -- PCM OUTPUT
The PCM energizes the radiator fans through either the low or high speed radiator fan relay. The PCM controls the ground circuit for the solenoid side of the relay Power for both relay solenoids is supplied through a 10 amp fuse in the PDC. Power for both relay contacts is supplied power through a 40 amp fuse in the PDC.

The PCM monitors the A/C compressor discharge (high side) pressure through the air conditioning pressure transducer. Depending on engine coolant temperature and A/C system high side pressure, both fans operate at either low or high speed.

The radiator fan relays are located in the PDC. The inside top of the PDC cover has a label showing relay and fuse location.

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.