Car Electronics Overview

 The electrical system is responsible for controlling all the systems in your car. We'll break the car down into 6 components:

1. Power Distribution

2. Wiring Harness 

3. Connectors

4. Electrical Modules

5. Wiring Diagram, 

6. CANBUS network.

The circuits will flow from positive to negative side of the battery. Once the vehicle started, the alternator keep all the charge of battery, and then electricity flows through power distribution unit then wiring harness. 

Power in a wiring diagram starts at the top and flows through the bottom, which goes from the power source to the bottom. Sometimes power will flow through links, fuses, and relays, and lines are actual wires and the colors of the lines on the document are the actual colors of the wire. Lines are fed power to each motor. In order to get a window up and down a power master switch will supply power on one side and ground on the other side. 

The intelligent power distribution takes power from positive battery terminal then distribute them into smaller circuits through fuses, then into relays following into circuit functions, then sending signals to indiviual requirements. Make sure the fuses are individually removable, which will pop the fuse. Larger links are more suspectible to blowing, some are automatic circuit breakers when the wam up they break the circuit. Relay separates the smaller amperage circuit from the larger amperage circuit. The relay works through electromagnet powered up by ECU signal which allow contacts to connect to each other which allows a signal/lightbullb to turn on. 

The thicker the wire, the more current it's going to carry. Rail runs from the positive lead and powers smaller fuses. Thick wires bring in current feed. Relays do come in all shapes and sizes, meant for current applications (horns, instrucment, etc.) The individual connectors in PCB are controlled by the CAN bus. The negative side is called ground. Power is transmitted trhoguh the wiring harness.

The wiring diagram can tell us the exact location of each harness. Wiring harness carries a voltae or signal on device, wrapped in conduit/electrical tape to keep it insulated. The weak point or one of it is definetly the harness because it is so brittle. You can use the wire color tofigure out where on the harness things aren't working. I can pull wires for voltages, to see if anything if coming out of the ECU or try to do a continuity test with the voltmeter. You can also splice into the electrical system too just need a watertight connection. 

Connectors are responsible for conducting electricity through terminals. Again, the wiring diagram helps immensely. Compare the wiring diagreaam to the pinout diagram, in order to see exactly which pin correlates to which wire. Each car can havedozens of computers with a body control module, engine control module, immobbilizer, amplifier, etc. The black box is an immobilizer. Most datasheets are avaialble, and this module has relays and power distribution module, with a data sheet with a block diagram and a pinout. There are drivvers for fuel injector, with capacitors/etc. 

The airbag computer have 2 giant capacitors, storing enough energy to fire airbag. Huge hunks of aluminium usually acts as heat sink. Radios have. alot of capacitors and transformers in order to amplify radio signals. You can use a heat gun to heat things up and clean up the solder. A lot of problems can fbe figure out if power is coming to the body of the car, and measure all the voltages. Find the wire that brings in power, and find the specific pin. We connect and touch things against ground. 

The next thing to check to see if the motor can be grounded and find the corresponding pins. If there's no voltag, this means that we have a grounding issue. We check the connector and check the continuity between connector and other wires. Test all the connections if the grounding test fails. Make the fix, then verify your measuremnts.

There really isn't too many wires compared to the number of functions that you have in your car, since modules communicate through a network called the CANBus. We can simplify car electronics system through a network. We can attach everything into a network with a CAN high and CAN low and each module can talk through these 2 wires only. 

CANBus is widely adopted system across all automotive signals. CAN high and CAN Low are differential signals based on the voltage. Combining binary data can get a full frame of data. The most important bits are start of frame, and end of frame, and actual data to transmit, and address of module that you want to talk with from/to. Without the CAN bus then we need more wires. We can also access elements from the CANBus when doing diagnostics. The software can access certain commands and see if those commands work or not when connected to the car. We can also graph a lot of sensors, etc. 

Imagine the car is a human body. CAN is the control area network system, is the nervous system facilitating communication between all parts of the body. CAN bus can be in ECU, airbag, etc. CAN allows ECUs to communicate with each other without complex dedicated wiring, allowing several features to communicate alone without causing an overload to the computer. 

CAN is low cost. ECUs communicate via CAN signal interface. The CANBus system allows for error diagnosis. The system is robust towards failure of subsystems and electromacgnetic interference. CAN messages are prioritized based on IDs. Each ECU contains a chip allowing it to recieve all transmitted messages, and act accordingly. 

To understand how CAN works, let's break down everything. There are 8 key parts, SOF (start of frame telling ECUs message is coming), CAN Id, RTR (remote transmission request), Control (informs length of data in bytes), data (contains actual data values need to be scaled), CRC (cyclic redundancy check checks data integrity), ACK (Checks if the CRC and data is ok), EOF (end of function). SA J1939 is standard for buses, trucks, and all other vehicles. J1939 is identified by a suspect parameter number. 

OBD (on-board diagnostic) is what mechanics use to identify what is wrong with your car, specifying a number of stanadard diagnostic trouble code. OBD2 supports data on many basic real-time parameters, also used in real-time vehicle telematics and CAN data loggers. To log this data, the CAN loggers request the data and when using the CAN logger, this can easily be configured in CANBus. 

CANOpen is used for industrial automation applications, and builds on CAN, the physical layer, and the data link layer. This means the data logger is able to log data from CAN Open applications. 

Bosch relays you can lock out and trigger a lot of things such as the starter, ignition, etc. You trigger these relays with a low amperage input and that in turn feeds your load. 

IN automotive electronics, ECU is something that controls the electrical system/subsystems in the vehicle. ECU is a general term for computer modules that recieve input from sensors and control different functions. 

ECU consists of RAM, microprocessor, ROM, and other interfaces, and protected to prevent unwanted tempering. 

BCM (Body Control Module) is attached tot he junction bllock under the driver's side of the instrument panel, utilizing circuitry and monitor many sensor and switch inputs throughout the vehicle. It controls lighting, AC, Use Information, etc. The Passenger Door Module (PDM) is located behind the right door trim panel and these modules control power door locks, windows, windows, etc. Airbaag control module is behind the shifter assembly. The microprocessor contains the circuits and supplemental restraint system. EVIC is the electronic vehicle information center, located within overhead console. It's an interactive display system, giving driver information. The instrument cluster is located in the left dashboard, and provides gauge and indicator control, and uses the PCI bus to get most of the data needed to control indicated. 

TCM, or the transmission control module, is located on the right side of the engine compartement near the firewall, or on the left side of the instrument panel, controlling all electronic operations of the transmission. The controller antilock brakes are attached to the hydraulic control unit, and controls the AVS and electronic brake distribution (EBD). 

PCM, or powertrain control module, is a pre-programmed digital computer that regulates ignition timing, speed control, transmission features, etc.