Auto Channel

Alternator

The alternator (generator) supplies electric power for the vehicle's electric systems and also recharges the battery when the engine is running. If it fails, the engine will continue to run using the battery power, but the car will eventually stop as soon as the battery will be completely discharged. When the alternator fails, there is a warning light on the instrument panel that comes on with the engine running. Usually it's something like or "charge" warning light. If you see that sign on your instrument panel while driving, have your vehicle inspected before it dies on you

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Ball Joint

A ball joint is a part of a vehicle front suspension. Most cars have one or two ball joints at each front wheel. When a ball joint becomes bad, a vehicle could be unsafe to drive; a ball joint, when badly worn, can disjoin causing the vehicle to lose control unexpectedly. One of the possible indication of a bad ball joint could be a knocking noise coming from the front end, particularly while driving over bumps or making sharp turns. If you suspect your vehicle has a bad ball joint or any other suspension component, have your car inspected as soon as you can, it can be unsafe to drive. It's recommended to check the vehicle's chassis in a garage on a lift at least once a year to discover potential problems with suspension, brakes and other components.

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Battery

The battery provides electric power to start the car. I get many questions like "My car doesn't start, it only makes a click-click noise when I'm trying to start it" - this is most likely the result of the battery having decided to quit. Unfortunately, usually it happens unexpectedly - the battery just stops working one day. If your vehicle doesn't start and you suspect the battery, there is a simple way to check it. Try switching the wipers on - if they move very slowly, a lot slower than usual (too low voltage) the battery is probably discharged or dead.

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Continuously Variable Transmission

Continuously Variable Transmission (CVT) shares some components and principles to a conventional automatic transmission - it has a torque converter and operated by the transmission fluid pressure. The difference is that it has no gears. Instead there are two pulleys connected by a special belt. The size of each of the pulleys can be varied within certain limits using hydraulic pressure and as a result the gear ratio can be changed continuously. It drives like conventional automatic transmission with the difference that there is no shifting - gear ration changes continuously according to the driving conditions. Nissan Murano, Saturn Vue, Audi A4, Honda Civic Hybrid are among the few models featuring the CVT.

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Driven-by-wire

If older vehicles use cable or mechanical link to operate the throttle, many of the new cars have electronic, "driven-by-wire" throttle control. This means that there is no longer a mechanical connection between the gas pedal and the throttle: There is a sensor connected to the gas pedal. Once you step on the gas pedal, it sends the signal to the vehicle's computer, which in turn opens the throttle using an electronic actuator. The actuator helps optimize engine performance by keeping the emission level low. Also, there is no more need for additional idle control and cruise control systems - these functions are controlled by the vehicle computer using the same electronic throttle actuator.

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EGR system

The EGR system (Exhaust Gas Recirculation system) is designed to reduce emissions. To be precise, it lowers the amount of nitrogen oxides (NOx) in the exhaust emissions. Nitrogen oxides are formed at very high combustion temperatures. What the EGR system actually does is direct part of the exhaust gases back into the intake manifold, which in turn helps reduce the combustion temperature and consequently lower the amount of NOx in the exhaust gases. The EGR flow is controlled by the engine computer which opens or closes the EGR valve depending on the operating conditions. One of the most common problems related to EGR is that the passages or the EGR valve itself getting clogged with carbon deposits causing restrictions to the EGR gas flow. This turns the "check engine" light on and sets the code, for example, PO401 - insufficient EGR flow (this was a common problem for the Acura / Honda V6 engine, for example). This problem happens mostly if a car is driven for only short trips so it can't warm up fully, or when the oil is not changed regularly.

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Overdrive

Generally speaking, overdrive (O/D) is the highest gear in the transmission. On most cars the automatic transmission has three or four speeds and overdrive (which is fourth or fifth speed accordingly). Overdrive allows the engine to have less rpm with higher speed for better fuel efficiency. When you switch it ON, you allow the transmission to shift into overdrive mode after a certain speed has been reached (usually 30-40 mph depending on the load). When it's OFF, you limit transmission shifting to third or fourth speed, not allowing the transmission to shift into overdrive.
In normal driving conditions the overdrive should be always ON. You may need to switch it OFF if you drive in a mountainous area.
[The automatic transmission automatically shifts from O/D to the lower gear when it feels more load. When it feels less load it shifts back to O/D, but under certain conditions, e.g., driving uphill or towing a trailer, the transmission cannot decide whether to stay in O/D or shift into 3rd speed and it starts shifting back and forth. That's the time when you may switch the O/D off and help the transmission to decide].
You also may need to switch the Overdrive OFF when you want to slow down using the engine braking, for example, when driving downhill. For more details, check your owner's manual.

[Source: samarins.com]