What Is a Vehicle Control Unit (ECU)? Functions and Duties of Control Units in Vehicles
In this video, we explain the control units in vehicles, what they do, and their roles on the vehicle.
In automotive electronics, the electronic control unit (ECU) is an embedded system that controls one or more electrical systems or subsystems in a vehicle. ECU is a general term for any of the many computer modules that receive input from sensors in the vehicle and control different electrical functions.
The ECU system is the brain of the vehicle. As automobiles become more complex and are equipped with more sensors and functions, dozens of different electronic control units may be active in a single vehicle.
An ECU generally consists of an 8-bit microprocessor, random access memory (RAM), read-only memory (ROM), and an input/output interface. ECUs can be updated by the manufacturer or a third party.
They are usually protected to prevent unwanted, unauthorized changes. As an example, electronic control module types for the Jeep Grand Cherokee WJ.
Body Control Module (BCM) is mounted on the connector block below the driver side of the instrument cluster. BCM uses integrated circuits and information carried on the programmable communication interface PCI data bus network. Together with wired input, it monitors many sensors and switch inputs across the vehicle. BCM supports many body electrical features such as interior lighting, exterior lighting, intermittent wipers, remote radio, accessory delay, and heated seats.
Passenger Door Module (PDM) is located behind the right door trim panel integrated into the door lock assembly. The door module controls various electronic features such as power door locks, power windows, power mirrors, dome lighting, and lock motor.
Airbag Control Module (ACM) is located below the center control console behind the gear shifter. The microprocessor in the airbag control module contains supplemental restraint system logic circuits and controls all supplemental restraint system components. In other words, control of airbag systems in vehicles is handled within this ECU.
Electronic Vehicle Information Center (EVIC) module is positioned in the overhead console. The electronic vehicle information center is an interactive display system. It gives the driver information such as compass, temperature, and trip data.
Sunroof Module (SM) is located in the roof console as part of the sunroof assembly. The sunroof module controls sunroof open/close and ventilation functions.
Rain Sensor Module (RSM) is located inside the windshield between the rearview mirror mount button and the windshield header, hidden behind a molded plastic cover cap on the module housing. The microprocessor-based rain sensor module detects moisture on the patterned area outside the windshield and initiates wipe detection/clearing to the body control module BCM.
Instrument Cluster Module (IC) is located in the left front panel of the instrument panel. The instrument cluster provides gauge display and control. The instrument cluster uses the PCI data bus to obtain most, if not all, information needed to control gauges and indicators.
Driver Door Module (DDM) is located behind the left door trim panel integrated into the door lock assembly. The driver door module controls various electronic features such as power door locks, power windows, power mirrors, dome lighting, and liftgate motor.
Heated Seat Module (HSM) is mounted on a bracket placed between the power seat rail and seat cushion frame under the driver seat. The heated seat module HSM performs heated seat functions.
Memory Heated Seat Module (MSM) is mounted on a bracket placed between the power seat rail and seat cushion frame under the driver seat. The memory heated seat module performs memory seat and heated seat functions.
Adjustable Pedal Module (APM) is located below or above the brake pedal. The adjustable pedals module APM controls adjustable pedal operation.
Sentry Key Immobilizer Module (SKIM) is mounted on the underside of the steering column shroud below the steering column opening cover. The immobilizer module contains a radio frequency RF transceiver and a microprocessor. The immobilizer module transmits RF signals to the key transponder through the tuned antenna ring integrated into the SKIM housing and receives RF signals from it.
Transmission Control Module (TCM) is mounted on the right side of the engine compartment near the firewall, on the inner fender, or on the left side of the instrument panel. The transmission control module controls all electronic transmission operations. TCM receives information about vehicle operation from both direct and indirect inputs and selects the transmission operating mode.
Controller Antilock Brakes (CAB) is mounted under the hood in front of the master cylinder on the hydraulic control unit HCU. Controller antilock brakes CAB also controls ABS and electronic brake distribution EBD.
Powertrain Control Module (PCM) is located on the right rear side of the engine compartment on the hood panel. PCM is a pre-programmed digital computer with triple microprocessors. It regulates ignition timing, air-fuel ratio, emission control devices, charging system, certain transmission features, speed control, A/C compressor clutch, and idle speed.
