Page 337 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

The specific pinout and communication protocol utilized depend on the make, model, and year of the vehicle. In
the United States, OBD-II has been the standard since 1996 for vehicles sold, and it typically employs pins 4 and
5 for ground, pin 16 for battery voltage, and pins 6 and 14 for CAN bus communication. Other pins may be utilized
for specific functions or protocols.
diagram of emission control system

Flow diagram of control systems-terminal arrangement of ECM
The Engine Control Module (ECM) is a black box-like electronic part located in the instrument panel box near
the driver’s seat. It contains a microprocessor, an Analog-to-Digital converter (A/D converter), and input/output
components. The ignition switch supplies current to the battery. The ECM is connected to various electronic
sensors and switches on the engine, and all related circuits are grounded to the engine. The ECM is responsible
for controlling the engine’s overall operation.

The Electronic Control Module (ECM) functions similarly to the cerebellum in the brain. It receives sensory
information from various sensors, much like how the cerebellum receives situational sensations from the body’s
senses. The ECM then analyzes this information, makes decisions, and sends commands to ensure the right
actions are taken. For example, sensors on the engine transmit data about its conditions to the ECM, which
processes the information and sends appropriate signals back to control various functions, such as fuel injection.
The ECM stores standard data about the engine’s entire operation, including functions like four-stroke operation,
cooling, lubrication, and fuel systems. If the engine deviates from this standard data, the ECM diagnoses faults
and sends necessary signals. In serious malfunctions, it can shut down the engine. It also controls ignition timing.
The ECM is not serviceable, and if it malfunctions, it needs to be replaced.

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CITS : Automotive - Mechanic Diesel - Lesson 98 - 103