Powertrain Management: Description and Operation

PURPOSE
The powertrain management system electronically regulates the air/fuel mixture, idle speed, ignition timing, various emission control devices, and in many cases, transmission shift points and torque converter lock-up, to optimize engine performance, fuel economy, and to reduce exhaust emissions. A computer controller known as a Powertrain Control Module (PCM) monitors various engine and vehicle operating conditions, processes the information, and generates outputs to control the following systems/components:

^ Electronic Fuel Injection System
^ Ignition Control - Electronic Spark Timing (EST)
^ Electronic Spark Control (ESC - Knock sensor controlled ignition retard)
^ EVAP System Purge Control
^ Air Conditioning Compressor Clutch
^ Engine Cooling Fans

INFORMATION STRUCTURE
Information in this section is divided into sub-headings according to the following four major sub-systems of powertrain management:

COMPUTERS AND CONTROL SYSTEMS
Addresses the on-board computer system and components as related to powertrain management. Consult this section for information regarding on-board diagnostics, sensor inputs, computer outputs, etc.

EMISSION CONTROL DEVICES
Addresses emission related systems and components only. Includes (but is not limited to), Evaporative Emission (EVAP) systems, Positive Crankcase Ventilation (PCV) systems, Catalytic Converter, etc.

FUEL SUPPLY AND AIR INDUCTION SYSTEMS
Focuses on systems and components related to fuel and intake air delivery.

IGNITION SYSTEM
Focuses on primary and secondary ignition systems and components.