Car dictionary: automotive terms

Updated: May 6, 2014


Video: Toyota NZ

The Antilock Braking System or ABS is designed to help the driver maintain the steering control during hard braking. Without the ABS, a car would spin out of control when the wheels lock up during hard braking, especially on a slippery surface. The ABS uses wheel speed sensors to monitor the speed of each wheel. If the ABS senses that any of the wheels start locking up during braking, it quickly releases and applies the braking pressure to the affected wheel, preventing it from locking. If the ABS system doesn't work properly, you will see the ABS warning light on the dash.


Volkswagen 2.0 TSI engine Alternator
Volkswagen 2.0 TSI engine alternator

An alternator supplies the electric power for the vehicle's electric systems and charges the battery when the engine is running. See the cut-away of an alternator. An alternator is bolted to the engine and rotated by a drive belt connected to the engine crankshaft.
If the alternator fails, the warning light battery symbol or "CHARGE" icon comes on in the instrument panel.
Alternator problems are common. If the alternator fails it needs to be rebuilt or replaced. Replacing the alternator can cost from $360 to $800.

Ball Joint

Ball Joint
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. A ball joint is lubricated inside and sealed with a rubber boot. When a ball joint becomes bad, a vehicle could be unsafe to drive; a ball joint, when badly worn, can separate 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.

Bank 1 or Bank 2

Cylinder banks
Typically, the engine bank that
contains cylinder 1 is called Bank 1

The engine Bank is the group of cylinders aligned together. The term Bank 1 usually refers to the bank of the engine that contains the cylinder number 1.
In an inline 4-cylinder engine cylinders are grouped together, so there is typically only one bank (Bank 1), although in some cars even an inline 4-cylinder engine might be split in two banks.
A V6 or V8 engine has two banks (see the diagram), each with three or four cylinders respectively. Usually, in a V6 or V8 engine, the bank that contains the cylinder 1 is called Bank 1 and the opposite bank is called Bank 2. Unfortunately, there is no standard practice to identify bank 1 and bank 2, as different manufacturers assign bank numbers differently. In most front-wheel drive cars with a transversely-installed V6 engine, bank 1 is closer to the firewall, while the bank 2 is closer to the front of the vehicle.


Car battery
Car battery

The battery provides electric power to start the car. If your car doesn't start, the battery is the first thing that needs to be checked. If you have no testing equipment, here is another way to check the battery state of charge: Without starting the engine, turn the windshield wipers on. If the battery is low on charge, you will notice that your wipers move slowly, much slower than usual. You also may notice that lights on the dash appear dim. If your battery is low on charge, it needs to be recharged. When the car is running, the battery charges automatically from the power supplied by the alternator. To start a car with a discharged battery, the car needs to be boosted. On average, the battery lasts from 3 to 6 years. It lasts longer if the car is driven daily. If the car is parked for a long time without starting, the battery deteriorates faster. An early sign of the deteriorated battery is slow cranking when starting the car. Replacing the battery is not very expensive.

Catalytic converter

Catalytic converter
Charcoal canister

A catalytic converter is a very important part of the vehicle emission control system. A catalytic converter is installed in the exhaust, right after the exhaust manifold. Inside the catalytic converter, there is a honeycomb-like ceramic block covered by a special catalyst material. The main purpose of the catalytic converter is to chemically convert harmful exhaust emissions into harmless gases. Without a catalytic converter, the vehicle won't pass the emission test. The engine computer constantly monitors the performance of the catalytic converter. For this purpose, there are two oxygen sensors installed before and after the catalytic converter. These sensors measure the level of oxygen before and after the catalytic converter. The engine computer compares the signals from both sensors and if it the catalytic converter doesn't perform properly, the engine computer illuminates the "Check Engine" light on the dash. Replacing the catalytic converter is very expensive.

Charcoal canister

Charcoal Canister
Charcoal canister

A charcoal canister is a part of the vehicle's Evaporative System. The Evaporative System (EVAP) prevents the fuel vapors from the fuel tank from escaping into the atmosphere. The EVAP system draws the fuel vapors from the fuel tank and temporarily stores them in the charcoal canister. A charcoal canister is filled with charcoal pellets that can absorb fuel vapors. When the engine is running and other conditions allow, the fuel vapors are purged from the charcoal canister into the engine air intake to be burned. The EVAP system is controlled by the engine computer and if there is a problem with the charcoal canister, the Check Engine light will illuminate on the dash.

Control arm

Control arm
Front control arm, Toyota Camry
Lower control arm
Lower control arm. Ford F150

A control arm is a part of the front suspension. Some cars have one control control arm on each side; other vehicles, including many trucks have two (upper and lower) control arms on each side of the front suspension. The internal side of the control arm is connected to a vehicle's body or a frame through the rubber bushings (control arm bushings). An outer end of the control arm holds a ball joint. A ball joint could be bolted to or pressed into the control arm. Sometimes, a ball joint is an integral part of the control arm and if it goes bad the whole control arm must be replaced.
One of the common problems with control arms is when the control arm bushings wear out. Sometimes the bushing can be replaced separately. Typically they have to be pressed into the control arm.
In some cars if the control arm bushings go bad, the whole control arm has to be replaced as it comes as an assembly.
After the control arm bushings or the whole control arm is replaced, the wheel alignment must be performed on most cars.

CV joint

CV Joint boot looks OK
CV joint.

All front-wheel drive cars as well as some four-wheel drive vehicles have Constant Velocity joints or CV joints on both ends of the front drive shafts; the inner CV joints connect the drive shafts to the transmission and the outer CV joints connect the drive wheels to the drive shafts. The CV joints are needed to transfer the torque at a constant speed to the steered wheels as well as to accommodate up and down motion of the suspension. A CV joint is packed with a grease and sealed tight by a rubber or plastic boot. A CV joint doesn't need any maintenance and can last very long, as long as the protective CV joint boot is not damaged. Read full article: CV joint

EGR system

EGR system diagram
EGR system diagram

The EGR system (Exhaust Gas Recirculation system) is designed to lowers the amount of nitrogen oxides (NOx) in the exhaust gases.
Nitrogen oxides are formed at very high combustion temperatures. The EGR system re-routes a part of the exhaust gases back into the intake manifold, diluting the air/fuel mixture. As the exhaust gases are not combustible, mixing them with the air/fuel charge reduces the combustion temperature. The EGR flow is controlled by the EGR valve, that is operated by the engine computer. The EGR valve is closed at idle, or during hard acceleration. The EGR valve opens during steady cruising speed. The EGR system problems are very common. When the EGR system doesn't function properly, the vehicle may have variety of driveability issues as well as the "Check Engine" light illuminated on the dash.

EGR valve

Ford EGR Valve
Ford EGR vacuum-operated valve

The EGR valve is the main component of the EGR system (see above). The EGR valve can be operated by vacuum, like in this photo, or electrically. The EGR valve opens and closes gradually, in small steps. This process is controlled by the engine computer. The EGR valve can be tested with a scan tool using the following technique: with the engine running at idle, the EGR valve gradually commanded open from the scan tool. If the EGR valve works properly, the engine should start running rough with RPMs fluctuating up and down as the EGR valve gradually opens. When the EGR closes, the engine should run smoother. With the EGR valve completely closed, the engine idle speed should be stable. Replacing the EGR valve could run from $250 to $600, depending on the vehicle design.

Ground connection

Ground connection
Ground connection

Whenever a car has some electrical problems, you often hear about a ground connection or 'ground'. Modern cars have a 12-volt electrical system where the positive battery terminal (+12V or 'power') is distributed through wiring and fuses, while the battery negative "-" terminal is connected to the car's body ('ground'); thus a car body acts as a conductor. Most of the electrical consumers in a car receive their positive voltage (+12V) through the fuses and wiring, while the negative side is usually connected to a car body, like the ground terminals in the photo. A bad connection at one of the ground terminals can cause various weird or hard to trace electrical problems. For that reason, with any electrical issues, 'power' (+12V) and 'ground' are usually checked first. Sometimes a ground terminal can get loose or corroded causing poor connection.

Head gasket

Head gasket
Head gasket

A head gasket is installed between the cylinder head and the engine block. It's not a very expensive part, but it has a very important function: it seals the combustion chambers as well as the oil and coolant passages that run between the engine block and cylinder head.
Head gasket failures are often caused by overheating, for example, when the engine is low on coolant (antifreeze) or when the radiator fans don't work. Other reasons include: a detonation (pinging, spark knock), lean air-fuel mixture, design flaws, etc.
Symptoms of a blown head gasket include: Coolant present in engine oil (engine oil has a "coffee with milk" color ) see the photo, white steam (smoke) with a strong smell of coolant from the exhaust, bubbling in the cooling system, coolant boiling over in the overflow tank, loss of coolant with no visible leaks, overheating, no-start after the engine has been overheated.
The head gasket repair is quite expensive because of the amount of labor involved. If the engine hasn't been overheated and there is no other damage, the repair could cost $150-$300 for parts, another $150-$300 to have the cylinder head checked and resurfaced, plus $400-$700 for labor. A new head gasket itself is not very expensive, however many other parts like cam seals, valve cover gasket, intake gaskets often need to be replaced too. If the engine was severely overheated, it might be cheaper to replace the whole engine with a used or rebuilt unit. How is a blown head gasket diagnosed? Usually a diagnostic involves performing a cooling system pressure test or checking for exhaust gases in the cooling system with a gas analyzer. The compression and cylinder leak-down tests can also tell a lot.
Replacing a head gasket is a big job, as the cylinder head with manifolds has to come off. Once removed, the cylinder head needs to be tested in a machine shop and re-surfaced if needed. The cylinder block mating surface needs to be checked and cleaned. When a rebuilt cylinder head is installed, the timing may need to be re-set and valves re-adjusted.