General System Description

INPUT OPERATION
The PCM determines current engine operating conditions by interpreting inputs from various sensors and switches.

Sensor Inputs
- Engine Coolant Temperature (ECT) Sensor
- Manifold Absolute Pressure (MAP) Sensor
- Throttle Position Sensor (TPS)
- Heated Oxygen Sensor (O2S)
- Vehicle Speed Sensor (VSS)
- Distributor (Hall Effect) Pick-up
- Throttle Body Temperature Sensor

Other Inputs
- A/C Request
- Brake Switch
- Park/Neutral Switch
- Speed Control System Controls
- Self Test Input (STI)
- Battery Voltage (B+)

OUTPUT OPERATION
The PCM then actuates various output devices to achieve the best compromise between power, fuel consumption, and emissions.

Outputs
- Air Conditioning Clutch (ACC) Relay
- Automatic Shut Down (ASD) And Fuel Pump Relays
- EVAP Canister Purge Solenoid
- Data Link (Diagnostic) Connector
- Electronic EGR Transducer (EET)
- Fuel Injector
- Generator Field
- Idle Air Control (IAC) Motor
- Ignition Coil
- Malfunction Indicator Lamp (MIL), (previously called "Check Engine" lamp)
- Radiator Fan Relay
- Speed Control (S/C) Solenoids
- Tachometer Output
- Torque Converter Clutch (TCC) Solenoid

MODES OF OPERATION
Open Loop Modes
- Ignition Switch ON (Zero RPM)
- Engine Start-Up
- Engine Warm-Up
- Wide Open Throttle (WOT)
- Ignition Switch OFF

NOTE: In OPEN LOOP modes the PCM receives input signals and controls outputs according to preset programming. The PCM Ignores Oxygen (H02S) sensor input during OPEN LOOP modes.

Closed Loop Modes
- Warm Idle
- Cruise
- Acceleration (Except Wide Open Throttle)
- Deceleration

NOTE: In CLOSED LOOP modes the PCM monitors the Oxygen Sensor (O2S), input, and adjusts injector pulse width to compensate for operating conditions.

Limp In Mode (See On-Board Diagnostic System)