Cruze L4-1.4L Turbo (2011)
Engine Control Module: Description and Operation
Engine Control Module Description
The engine control module (ECM) interacts with many emission related components and systems, and monitors the emission related components and
systems for deterioration. OBD II diagnostics monitor the system performance and a diagnostic trouble code (DTC) sets if the system performance
degrades.
The malfunction indicator lamp (MIL) operation and the DTC storage are dictated by the DTC type. A DTC is ranked as a type A or type B if the DTC
is emissions related. Type C is a non emissions related DTC.
The ECM is located in the engine compartment. The ECM is the control center of the engine controls system. The ECM controls the following
components:
*
The fuel injection system
*
The ignition system
*
The emission control systems
*
The on-board diagnostics
*
The A/C and fan systems
*
The throttle body motor system
The ECM constantly monitors the information from various sensors and other inputs, and controls the systems that affect the vehicle performance and the
emissions. The ECM also performs diagnostic tests on various parts of the system. The ECM can recognize operational conditions and alert the driver
via the MIL. When the ECM detects a malfunction, the ECM stores a DTC. The condition area is identified by the particular DTC that is set. This helps
the technician in making repairs.
ECM Function
The engine control module (ECM) can supply 5 V or 12 V to the various sensors or switches. This is done through pull-up resistors to the regulated
power supplies within the ECM. In some cases, even an ordinary shop voltmeter will not give an accurate reading because the resistance is too low.
Therefore, a DMM with at least 10 Mohm input impedance is required in order to ensure accurate voltage readings.
The ECM controls the output circuits by controlling the ground or the power feed circuit through the transistors or a device called an output driver
module.
EEPROM
The programmable read only memory (EEPROM), which can be erased electronically, is a permanent memory that is physically part of the engine
control module (ECM). The EEPROM contains program and calibration information that the ECM needs in order to control the powertrain operation.
Special equipment, as well as the correct program and calibration for the vehicle, are required in order to reprogram the ECM.
ECM Default Actions
When a malfunction occurs within the engine control system, the engine control module (ECM) maintains control of the system with default actions.
Default actions are calculated values, and/or calibrated default values, that are stored within the ECM. A certain level of engine performance is possible
when a malfunction occurs dependant on the default actions taken. The ECM default actions prevent a complete loss of engine performance.
ECM Output Controls
The scan tool can control certain solenoids, valves, motors, and relays. The output controls can be found under the special functions selection of the scan
tool. Some output controls may be disabled by the engine control module (ECM) during certain types of vehicle operation.
Data Link Connector (DLC)
The data link connector (DLC) is a 16-pin connector that provides the technician with a means of accessing serial data for aid in the diagnosis. This
connector allows the technician to use a scan tool in order to monitor the various serial data parameters, and display the DTC information. The DLC is
located inside the drivers compartment, underneath the dash.
Malfunction Indicator Lamp (MIL)
The malfunction indicator lamp (MIL) is located on the instrument panel cluster, or the driver information center. The MIL is controlled by the engine
control module (ECM) and illuminates when the ECM detects a condition that affects the vehicle emissions.
ECM Service Precautions
