Part of Lesson Plan: **Typical Computerized Engine Control Operation (updated) by Sergio Marquez

Activity Overview / Details

Have students follow along using the textbook ( Thomson Delmar Learning, "Automotive Technology: A Systems Approach," 4th edition ), pages 838-840.

Start by explaining that once the ECM/PCM has determined what adjustment or action needs to be made in any of the engine controlled systems, for example, Fuel delivery, Air injection, Evaporation Control, EGR Flow, Idle Speed, and Ignition Timing. Then the ECM/PCM computer commands actions as needed:

Fuel Injectors: These electronic solenoids valves deliver the correct fuel amount to the intake port, in an atomized spray, for the engine conditions at that precise time. You can find the fuel injectors on the intake manifold before the cylinder head. See fig. 34-1.

Idle Air Control (IAC) Idle Speed: These Actuators are small electric motors, that open the throttle on (Carburated) or open an air passage on (Fuel Injection) to increase idle speed. You can find the (IAC) on or close to the throttle body. See Fig. 34-2.

Ignition module: This module is a small electronic on and off switching device that is triggered by a signal from the ECM/PCM, to adjust the timing and spark duration according to engine conditions. The ignition module may be a seperate unit or may  be part of the ECM/PCM computer. You can find the ignition module on a distributor, DIS coil pack, or as part of the ECM/PCM. See Fig. 34-3.

EGR Flow Solenoids: The EGR flow on early vehicles is controlled by an electronic vacuum valve solenoid. This solenoid valve supplies manifold vacuum to the EGR valve when EGR is required or vent vacuum when EGR is not required. You can find this solenoid close to the EGR valve. On late vehicles the EGR valve its self is an electronic actuator (electric steper motor). See figures 34-4 and 34-5.

Evaporative Emission (EVAP) Canister Purge Valve: This Valve is controlled by a purge solenoid. The valve controls when stored fuel vapors in the charcoal canister are drawn into the engine and burned. The ECM/PCM computer only activates this purge solenoid to open the valve when the engine is warm and above idle speed. You can find this purge solenoid in most cases close to the charcoal canister. See figures 34-6.

Air Management Solenoids (AIS) : Secondary air Bypass and diverter solenoids control the flow of air from the air injection pump (AIR) to either the exhaust manifold when cold (open loop) or the catalytic converter when warm (close loop). You can find this solenoids close to the air injection pump. See fig. 34-7.