Also called the "Malfunction Indicator Lamp" or (MIL), an illuminated CHECK ENGINE LIGHT means you vehicle has detected a potential emissions fault. The computer has logged one or more diagnostic trouble codes that correspond to the problem and turned on the warning lamp to alert you to the problem.
There is NO WAY to determine the nature of the problem without connecting a scan tool to the vehicle's diagnostic connector to read the fault code(s). Once this has been done, further diagnosis and testing may be required to isolate the fault so the correct parts(s) can be replaced.
Don't be alarmed by a CHECK ENGINE light. Often the problem is something minor that will NOT affect the way your engine runs, or you car's ability to start or drive. Depending on the nature of the fault, your engine may not run as good as it normally does, or it may use more fuel than usual. But usually the problem does NOT require immediate attention. You can continue to drive your car until it can be diagnosed.
Common reasons for the CHECK ENGINE light to come on include a loose gas cap, fouled spark plugs, dirty fuel injectors, the failure of an engine sensor such as the oxygen sensor, throttle position sensor or manifold absolute pressure sensor, or a problem in an emissions control system or device such as the EGR valve or catalytic converter.
For more information about CHECK ENGINE light problems, Click Here.
For more information about troubleshooting Check Engine Codes with a scan tool, Click Here..
If a warning light says OIL or you see a little icon of an oil can, DO NOT ignore this warning light. It means your engine is not getting normal oil pressure. Stop driving immediately, turn the engine off and check the engine's oil level. If low, add oil to bring the level up to the FULL mark on the dipstick.
The oil pressure warning light comes on when oil pressure drops below a minimum threshold (the exact pressure will vary from one vehicle to another). No engine will run very long if it runs out of oil. The bearings will run dry, overheat and seize, causing severe engine damage (spun bearings, damaged crankshaft journals, broken connecting rods, etc.).
The underlying cause of a low oil pressure warning light is usually a low oil level in the engine's crankcase. This, in turn, may be due to leaky gaskets or seals, or worn valve guides, piston rings and/or cylinders that are causing the engine to burn oil. Leaky gaskets and seals are usually not too expensive to replace (except for the rear main crankshaft seal which is difficult and expensive to replace). The only fix for a worn engine that is burning oil is to overhaul or replace the engine (very expensive!)
Other causes of an low oil pressure warning light include a worn oil pump or a faulty oil pressure sending unit.
For more information about your engine's lubrication system and causes of low oil pressure, Click Here.
A TEMP warning light or an icon of a thermometer is another warning lamp that you should NOT ignore. Stop driving immediately, turn the engine off and let the engine cool for at least 30 minutes. Then check the coolant level in the coolant reservoir or radiator.
CAUTION: DO NOT open the radiator cap on a hot engine. Hot water and/or steam can spray out and scald you.
The temperature warning lamp is on because your engine overheated. Continuing to drive can cause expensive engine damage (head gasket failure, cracks in the cylinder head, piston scuffing, valve stem galling, etc.)
Your engine may have overheated for a variety of reasons. The most common cause is a low coolant level (check the radiator, hoses and engine for coolant leaks). Other common causes include a stuck thermostat, a cooling fan that is not working, a failed water pump, obstructions that block airflow through the radiator (bugs, debris, plastic bags), a buildup of scale or sludge inside your cooling system, or overworking your engine or air conditioning system during unusually hot weather. Towing a heavy trailer or prolonged mountain driving may also cause your engine to run hotter than normal.
If the coolant level is low, add coolant after the engine has cooled off. Check for leaks. If you see none, start the engine and cautiously proceed. If the engine starts to overheat again, your engine may have an internal coolant leak (Bad news because it means a leaky head gasket or cracks in the cylinder head or block), or there is some other problem (bad thermostat, water pump, etc.).
If you see a coolant leak, you may be able to temporarily stop the leak by adding a can of cooling system sealer to the radiator. This may temporarily plug the leak or slow it down enough so you can continue driving until the leak can be fixed.
For more information about your cooling system and causes of a temperature warning light, Click Here.
The "GEN" or "ALT" warning light, or an icon of a battery usually means trouble (on some vehicles, a battery icon may illuminate if there is a charging system problem). You do NOT have to stop immediately, but your drive time will be limited: maybe 30 minutes or so during the daytime, or less after dark. The reason for this is that your car will be running off the battery alone, so as long as the battery lasts you can continue to drive. Eventually, the battery will go dead causing your fuel pump and/or ignition system to stop working. To maximize your remaining drive time, turn off all accessories to minimize the electrical drain on the battery. If you're driving at night, DO NOT turn off your lights (too dangerous!). Pull off at the first opportunity and seek help.
This warning light comes on when the charging system is NOT producing enough current or voltage to meet your vehicle's electrical needs. The cause may be a failed alternator or generator, a failed voltage regulator (if separate from the alternator), loose or corroded battery cables, or a broken or slipping drive belt. Turn the engine off and check the belt that turns the alternator. Caution: DO NOT get your fingers, clothing or tools near the belt(s) or pulleys while the engine is running.
If the belt appears to be intact and is turning the alternator, start the engine, and turn on the headlights. If the lights are dim, it verifies the charging system is not working -- probably due to a failed alternator or other electrical fault.
For more information about the operation of the charging system and charging diagnosis, Click Here.
More bad news -- but not always. The Brake Warning light may be one for one of two reasons: you forgot to release the parking brake, or your brake system has a potentially serious hydraulic problem that may make your vehicle unsafe to drive.
First, check the parking brake lever, handle or pedal. Make sure it is fully released. If that is not the problem, test the brakes by pressing on the brake pedal. If the light comes on only while pressing the pedal, it means one of the hydraulic circuits in the brake system has lost pressure -- probably because of a leak (bad brake hose, leaky disc brake caliper or drum brake wheel cylinder). Your vehicle may or not be able to stop with this kind of problem, making it unsafe to drive. If the pedal feels unusually low or goes to the floor, DO NOT attempt to drive the vehicle. Have it towed to a service facility for repairs (or fix it yourself).
If the Brake Warning light remains on all the time, the problem may be a low fluid level in the master brake cylinder reservoir. Many vehicles have a fluid level sensor that comes on if the fluid level gets low. This may also occur when braking hard or braking on an incline because of the fluid sloshing inside the reservoir. Check the brake fluid level and add fluid as needed if low. The brake system should also be inspected for leaks or worn linings.
For more information about brake problems, Click Here.
This warning lamp means your antilock brake system has detected a fault. When this happens, the ABS system logs one or more fault codes that correspond to the problem and turns on the ABS warning light. In most cases, it also temporarily DISABLES your ABS system. You vehicle should still brake and stop normally, but it will NOT have antilock braking when making a sudden panic stop or braking on wet or slick surfaces. You can continue driving, but you should have the problem diagnosed and repaired at your earliest convenience.
NOTE: If the Brake Warning light is also on, it may indicate a serious hydraulic problem with the brake system. Your vehicle may NOT be safe to drive (see the info on Brake Warning Light above).
For more information about ABS, Click Here.
This icon is a Low Tire Pressure Warning light. This light comes on if your vehicle's tire pressure monitoring system (TPMS) detects a tire that is more than 25 percent underinflated. Driving on a low tire can be dangerous because it increases the risk of a tire blowout. A low tire can also cause your vehicle to brake unevenly, pull to one side, handle poorly and get reduced fuel mileage. If the TPMS Low Tire Warning light is on, check the air pressure in your tires as soon as possible, and inflate them to the recommended pressure.
For more information about the TPMS Warning Light, Click Here
For more information about the Tire Pressure Monitor System, Click Here.
For more information about Tire Inflation Tips, Click Here.
This is a warning that you have a lamp out: a headlight, taillight, stop light or turn signal indicator. You can continue to drive your vehicle, but with reduced visibility and safety. Be warned that law enforcement officers may stop you and issue you a warning ticket or a safety violation ticket.
Check all the lights on your vehicle when it is safe to do so (not in the middle of the highway at night!), and replace any bulbs that have burned out. In some cases, the problem might be a corroded or loose socket, loose or corroded wiring, or a blown fuse.
For more information about lights, Click Here.
This little icon means somebody forgot to buckle up. Seat belts save lives so always use them, even on short trips. Driving without being bucked up may result in a ticket and a fine for a safety violation.
A warning light that looks like this or says SRS should NEVER come on unless there is a fault in your vehicle's air bag system (supplemental restraint system or SRS). Like the engine computer and ABS computer, the air bag control module runs a self-check every time the vehicle is driven. If it finds a fault in a crash sensor, one of the air bag modules, the wiring or itself, it will set a code, turn on the warning light and disable itself. You can drive the vehicle but the air bag(s) will NOT deploy should you be involved in an accident. You should have the problem diagnosed and repaired at your earliest convenience.
For more information about air bags, Click Here.
This is a reminder light that the fluid level is low in your windshield washer reservoir. Add fluid at your earliest convenience for safe driving.
For more information about windshield wipers, Click Here.
This is a reminder light that one of the doors (or tailgate) is not completely closed. Check all the doors (and tailgate) to make sure they are all latched properly. Sometimes the metal contacts that tell your vehicle the door is closed become dirty or corroded, causing a FALSE indication that a door is ajar. Cleaning the contacts will usually solve this kind of problem
Many late model vehicles have an oil change reminder light that comes on when the engine computer estimates the oil needs to be changed. The calculations are based on hours of engine operation, vehicle speed, ambient temperatures and other operating conditions. You do NOT have to change the oil immediately, but neither should you postpone the recommended maintenance too long. Oil should be changed every 3,000 miles for short trip city stop and go driving (especially during cold weather), or every 5,000 to 7,500 miles for mostly highway driving. Refer to your vehicle owners manual for the recommended service intervals.
Many service reminder lights have a RESET button that allows you to turn off the light and reset the interval period. On some, though, a scan tool is required to turn off and reset the light.
For more information about oil change intervals, Click Here.
Many vehicles have their own unique warning lights or icons to alert you when something is wrong. You can usually find these in the back of your vehicle owners manual. Note: The appearance of some warning lights will vary depending on the country where the vehicle is sold. Below are some typical warning lights for a late model Lexus (courtesy Toyota):