ΒCM means Body Control Module. Its the computer that control a lot of things in the car. When the BCM goes bad little things act quirky. Doors not unlocking, lights come on for no reason, car chimes and wont stop, rear hatch unlocks for no reason. Usually if you disconnect the battery for a bit it resets it and cures some of the faults.
While there are many different types of body control modules, they are generally alike, connecting sensors, switches and automatic reactions together in one computer system. These components are divided into inputs, such as sensor data about heat or speed, and outputs, or ways in which the body control module computer responds to control the vehicle's electronic functions. Inputs and outputs are further divided into analog and digital types of information, analog signals being used with modules that may change continuously (such as oil pressure) and digital signals being used for modules that can simply be on or off (like the headlights or the oil indication light).
Computer Tasks
The body control module computer itself performs many of the functions of a normal computer, including storing data, using RAM, and sending or receiving radio waves. It is the computer's job to regulate many of the systems and troubleshoot all of its component modules. Some modules are set by timer, which the the computer digitally keeps track of, while other modules like the anti-theft alarm need to be kept active even when the car is turned off. The body control module computer can also be in charge of keeping track of mileage and CO2 output.
When troubleshooting, a mechanic can often get pointed to the right area by the body control module system, which sends out a code that shows what module is not responding. At times the body control module computer can even diagnose itself and report specific problems.
The Body Control Module (BCM) supplies vehicle occupants with visual and audible information and controls various vehicle functions, To provide and receive information, the module is interfaced to the vehicle's serial bus communications network, the Chrysler Collision Detection (CCD) bus. This network consists of the powertrain control module (PCM), the Transmission Control Module (TCM) , the electro/mechanical instrument cluster (MIC) , the Airbag Control Module (ACM) , the Compass/mini-trip module and the Controller Antilock brake Module (CAB). The BCM is operational when battery power is supplied to the module. Ignition switch power is needed for ignition switch functions.
The body control module computer itself performs many of the functions of a normal computer, including storing data, using RAM, and sending or receiving radio waves. It is the computer's job to regulate many of the systems and troubleshoot all of its component modules. Some modules are set by timer, which the the computer digitally keeps track of, while other modules like the anti-theft alarm need to be kept active even when the car is turned off. The body control module computer can also be in charge of keeping track of mileage and CO2 output.
When troubleshooting, a mechanic can often get pointed to the right area by the body control module system, which sends out a code that shows what module is not responding. At times the body control module computer can even diagnose itself and report specific problems.
The Body Control Module (BCM) supplies vehicle occupants with visual and audible information and controls various vehicle functions, To provide and receive information, the module is interfaced to the vehicle's serial bus communications network, the Chrysler Collision Detection (CCD) bus. This network consists of the powertrain control module (PCM), the Transmission Control Module (TCM) , the electro/mechanical instrument cluster (MIC) , the Airbag Control Module (ACM) , the Compass/mini-trip module and the Controller Antilock brake Module (CAB). The BCM is operational when battery power is supplied to the module. Ignition switch power is needed for ignition switch functions.
The BCM provides the following features:
• Automatic door locks
• Battery protection
• Chimes
• Compass/mini-trip support
• Courtesy lamps
• BCM diagnostic support
• Door lock inhibit
• Headlamp time delay
• Ignition key lamp
• Illuminated entry
• Instrument panel dimming
• Mechanical instrument cluster support
• Power door locks (with/without remote keyless entry)
• Sliding door memory lock
• Vehicle Theft Security system (VTSS)
• Windshield wipers / washers (front and rear)
ECM (ENGINE CONTROL MODULE)
A car has at least one computer, but most have an engine control module (ECM), a body ride control unit, an ABS computer and a climate control computer. How many of these computers depend on the vehicle year, make and model and the options the vehicle has. If the vehicle does not have ABS brakes, it will not have an ABS computer. If the vehicle does not have climate control, it will not have a climate control computer.
Computers
The main computer is the engine control module. This may also be called the programmable control module. This computer takes its inputs and outputs through the various sensors on a vehicle. Sensors that give input give the computer information to send back to the engine via the output sensors.
Sensors
Some of the sensors include a mass air flow sensor, a coolant temp sensor, cam sensor, crank sensor, idle air control motor, EGR valve, throttle position sensor and a knock sensor. Each sensor has its own job in telling the computer what the conditions are such as air quantity and quality, temperature of the coolant and where the throttle is. The computer uses this information to make infinite changes to the air-fuel ratio, turn the fans on or off and change the idle speed and injector timing, along with many other things needed to run the vehicle.
Some of the sensors include a mass air flow sensor, a coolant temp sensor, cam sensor, crank sensor, idle air control motor, EGR valve, throttle position sensor and a knock sensor. Each sensor has its own job in telling the computer what the conditions are such as air quantity and quality, temperature of the coolant and where the throttle is. The computer uses this information to make infinite changes to the air-fuel ratio, turn the fans on or off and change the idle speed and injector timing, along with many other things needed to run the vehicle.
Diagnosis
This part of the vehicle's running system is diagnosed by the engine control module. It lets you know when something is not working by turning the "check engine" or "service engine soon" light on. The ECM sends "codes" that turn the light on. A scanner is hooked up to the port under the driver's side dash so that the codes can be read. Because you cannot visually see if a sensor is bad, you must rely on the ECM to tell you this information. The scanner will tell you which sensor is out of range or not working at all.
The ECM cannot diagnose itself. If an ECM goes bad, the vehicle may run badly or not at all. If the vehicle is running badly, a sensor could be out of range or bad, or the computer could be bad. When you hook up the scanner, you may get codes that do not exist or you may get codes that exist but do not make sense. This is a good sign that the computer itself is not working properly and should be replaced.
Conclusion
When you are working with the computer, extreme care must be taken. A friction shock from your fingers can damage the computer. Ground yourself before touching the computer. Most of today's computers must be programmed for the specific vehicle (getting "flashed"). You will need the VIN and the mileage of the car in addition to the numbers on the outside of the computer. The staffers at the auto parts store or the dealer should know that the PROM must be removed from the old computer and put into the new computer prior to "flashing" the computer. If they neglect to move the PROM or they say they will "flash" the computer without having your old computer, be sure to remind them that they cannot flash it without the PROM.
