Chevrolet Equinox Service Manual: Engine Control Module Description Engine Control Engine Control Module

The Engine Control Module (ECM) interacts with many emission related components andsystems, and monitors emission related components and systems for deterioration. OBDII diagnostics monitor the system performance and a diagnostic trouble code (DTC)sets if the system performance degrades. The ECM is part of a network and communicateswith various other vehicle control modules.

Malfunction indicator lamp (MIL) operation and DTC storage are dictated by the DTCtype. A DTC is ranked as a Type-A or Type-B if the DTC is emissions related. TypeC is a non-emissions related DTC.

The ECM is the control center of the engine controls system. Review the componentsand wiring diagrams in order to determine which systems are controlled by the ECM.

The ECM constantly monitors the information from various sensors and other inputs,and controls the systems that affect engine performance and emissions. The ECM alsoperforms diagnostic tests on various parts of the system and can turn on the MIL whenit recognizes an operational problem that affects emissions. When the ECM detectsa malfunction, the ECM stores a DTC. The condition area is identified by the particularDTC that is set.This aids the technician in making repairs.

ECM Function

The ECM can supply 5-V or 12-V to various sensors or switches. This is done throughpull-up resistors to regulated power supplies within the ECM. In some cases, evenan ordinary shop voltmeter will not give an accurate reading due to low input resistance.Therefore, a digital multimeter (DMM) with at least 10-megaohms input impedance isrequired in order to ensure accurate voltage readings.

The ECM controls the output circuits by controlling the ground or the power feed circuitthrough transistors or a device called an output driver module.

EEPROM

The electronically erasable programmable read only memory (EEPROM) is an integralpart of the ECM. The EEPROM contains program and calibration information that theECM needs in order to control engine operation.

Special equipment, as well as the correct program and calibration for the vehicle,are required in order to reprogram the ECM.

Data Link Connector (DLC)

The data link connector (DLC) provides serial data communication for ECM diagnosis.This connector allows the technician to use a scan tool in order to monitor variousserial data parameters, and display DTC information. The DLC is located inside thedriver's compartment, underneath the instrument panel.

Malfunction Indicator Lamp (MIL)

The malfunction indicator lamp (MIL) is inside the instrument panel cluster (IPC).The MIL is controlled by the ECM and illuminates when the ECM detects a conditionthat affects vehicle emissions.

ECM Service Precautions

The ECM, by design, can withstand normal current draws that are associated with vehicleoperations. However, care must be used in order to avoid overloading any of thesecircuits. When testing for opens or shorts, do not ground or apply voltage to anyof the ECM circuits unless the diagnostic procedure instructs you to do so. Thesecircuits should only be tested with a DMM unless the diagnostic procedure instructsotherwise.

Emissions Diagnosis For State I/M Programs

This OBD-II equipped vehicle is designed to diagnose any conditions that could leadto excessive levels of the following emissions:

Hydrocarbons (HC)Carbon monoxide (CO)Oxides of nitrogen (NOx)Evaporative emission (EVAP) system losses

Should this vehicle's on-board diagnostic system (ECM) detect a condition that couldresult in excessive emissions, the ECM turns ON the MIL and stores a DTC that is associatedwith the condition.

Aftermarket (Add-On) Electrical And Vacuum Equipment

Caution:Do not attach add-on vacuum operated equipment to thisvehicle. The use of add-on vacuum equipment may result in damage tovehicle components or systems.

Caution:Connect any add-on electrically operated equipment to thevehicle's electrical system at the 12 V battery (power and ground)in order to prevent damage to the vehicle.

Aftermarket, add-on, electrical and vacuum equipment is defined as any equipment installedon a vehicle after leaving the factory that connects to the vehicle's electrical orvacuum systems. No allowances have been made in the vehicle design for this type ofequipment.

Add-on electrical equipment, even when installed to these strict guidelines, may stillcause the powertrain system to malfunction. This may also include equipment not connectedto the vehicle electrical system, such as portable telephones and radios. Therefore,the first step in diagnosing any powertrain condition is to eliminate all of the aftermarketelectrical equipment from the vehicle. After this is done, if the problem still exists,the problem may be diagnosed in the normal manner.

Electrostatic Discharge (ESD) Damage

Note:In order to prevent possible electrostatic discharge damage to the ECM, DO NOT touchthe connector pins on the ECM.

The electronic components that are used in the control systems are often designedto carry very low voltage. These electronic components are susceptible to damage causedby electrostatic discharge. Less than 100-V of static electricity can cause damageto some electronic components. By comparison, it takes as much as 4,000-V for a personto even feel a static discharge.

There are several ways for a person to become statically charged. The most commonmethods of charging are by friction and by induction. An example of charging by frictionis a person sliding across a car seat.

Charging by induction occurs when a person with well insulated shoes stands near ahighly charged object and momentarily touches ground. Charges of the same polarityare drained off leaving the person highly charged with the opposite polarity. Staticcharges can cause damage, therefore, it is important to use care when handling andtesting electronic components.

Emissions Control Information Label

The underhood Vehicle Emissions Control Information Label contains important emissionspecifications. This identifies the year, the displacement of the engine in liters,and the class of the vehicle.

This label is located in the engine compartment of every General Motors vehicle. Ifthe label has been removed, it can be ordered from GM service parts operations (GMSPO).