Modes Of Operation

As input signals to PCM change, PCM adjusts its response to output devices. Modes of operation come in 2 types, open loop and closed loop. In open loop mode, PCM is not using input from Heated Oxygen Sensor (HO2S) and is responding to preset programming to determine injector pulse width and ignition timing. In closed loop mode, PCM adjusts ignition timing and uses input from HO2S to fine tune injector pulse width.

Following inputs may be used to determine PCM mode:

• A/C Control Positions
• A/C Switch
• Battery Voltage
• Brake Switch
• Camshaft Position (CMP) Sensor
• Crankshaft Position (CKP) Sensor
• Engine Coolant Temperature (ECT) Sensor
• Engine Speed (RPM)
• Heated Oxygen Sensor (HO2S)
• Intake Air Temperature (IAT) Sensor
• Manifold Absolute Pressure (MAP) Sensor
• Park/Neutral (P/N) Switch
• Starter Relay
• Throttle Position (TP) Sensor
• Vehicle Speed Sensor (VSS)

From these inputs, PCM determines which mode vehicle is in and responds appropriately. Not all inputs are used in all modes or by all models. Modes of operation are: