'Idiot' Enlightenment

Demystifying those pesky little instrument-panel warning lights that adorn your car's dashboard.

By Charles Plueddeman of MSN Autos

My father still calls them "idiot lights," referring to the array of warning indicators found in an automobile's instrument cluster that over the years have replaced analog gauges. By the 1970s, the only real "instruments" left on most dashboards were a speedometer and a gas gauge - possibly a tachometer. Fact is, warning lights are less expensive than gauges, and probably more attention-grabbing for the typically disengaged American driver. So they serve their purpose. But over the years, these clusters of illuminated icons have grown more complex and, as a result, more confusing. Heck, some of today's cars and trucks have more glowing dashboard lights than a Christmas tree. Knowing what they mean, and what to do when one flashes, is important for your safety and because the correct response could save you a huge repair bill.

Over the years, the number of illuminated icons that alert you to problems with your car has grown more complex and, as a result, more confusing. Knowing what to do when one flashes could save you a whole bunch of money.

You can view all of your car's instrument panel indicators by switching the ignition key to the "on" position (one click short of starting the engine). Each icon represents a system on the car, from a floating thermometer for engine temperature to a cross-section of a tire with an exclamation point for one of the newest warnings, low tire pressure. Your owner's manual offers a short explanation of what each means, and how you should react. But because you probably won't read your owner's manual, you should at least read the rest of this article, and become "idiot enlightened."

Low Oil Pressure: When this light activates, it means the oil, the lifeblood of your engine, has stopped circulating and severe damage could occur in just seconds. Pull out of traffic as quickly (yet safely) as possible and immediately turn off the engine. Open the hood and use the dipstick to check the oil level. If there's oil in the engine, but no pressure, the oil pump has likely failed. If there's no oil showing on the dipstick, you've either let the oil drop so low that the engine can't build up oil pressure, or there's been a problem - like an improperly installed oil filter - that caused most of the oil to drain from the engine. In any case, you risk serious mechanical damage and very expensive repairs if you restart the engine. Have the vehicle towed to a qualified shop for a diagnosis.

Engine Temperature: On late-model vehicles, this warning light is often coupled with an engine temperature gauge. If the needle goes into the red zone and the light comes on, your engine has a fever. Pull over and park. If there's steam coming from under the hood, or if antifreeze is leaking on the ground under the engine, you've likely blown a coolant hose. To avoid burning yourself, do not try to open the hood until the steam subsides. If there's no steam or obvious leak, open the hood and check the coolant level in the plastic reserve tank. If that's dry, you may need to add coolant to the radiator after it cools down. See your owner's manual for instructions.

Another cause of engine overheating could be a broken water-pump belt. If there are no obvious signs of trouble and the temperature gauge returns to normal after a few minutes, the engine may have overheated simply from working too hard. Pulling a trailer in the mountains on a hot day, for example, could overtax the cooling system. This could lead to engine damage, so after the engine cools, proceed at a slower speed and watch the temperature gauge closely.

Charging System: If the indicator comes on, it means that your battery is not being charged. The likely problem is a faulty alternator, which charges the battery as you drive, or a broken alternator drive belt. Your car will operate for some time on the power stored in the battery, so it's safe to drive it to a repair shop. To extend your range, turn off as many electrical accessories as possible, including the radio, heater or air conditioning fan, and windshield wipers and headlights (if you don't need them). Avoid using power windows and, if possible, don't turn off the engine, since it takes a lot of battery power to restart. Once the battery is dead so is the car, so don't ignore this light for long.

Low Tire Pressure: A tire-pressure-monitoring system has been standard equipment on all new vehicles since 2008. A sensor on each wheel monitors tire air pressure and triggers this warning light if the pressure drops to 25 percent below the specified cold inflation pressure. The idea is to warn you of low pressure before it becomes a critical safety issue. Some cars also have a graphic display that indicates which tire is low. Pull over as soon as possible. If the tire is really flat, you'll need to change it with the spare to continue. If you think you can drive safely on the tire, get to an air hose, fill the tire to its specified pressure, and then go to a service center and have the tire checked. It may be a slow leak that can be repaired. Note that a tire-pressure monitoring system is not a replacement for checking your tire pressure with an accurate gauge. Do it once a month.

The brake light could mean several things. First, make sure that the parking brake is fully released. If it stays on, make sure your brakes work properly and proceed cautiously to a service station.

Brake: This light usually has two functions. The first is to warn you that you're driving with your parking brake on. So the first step is to make sure that the parking brake is fully released. If the light stays on, or if it suddenly comes on while you are driving, the brake fluid level is probably low. If the brake pedal seems normal, check the brake fluid level (see your owner's manual) the next time you stop. If it's low, have the brake system checked for a leak or other problems, which could be as simple as worn brake pads. If the brake pedal does not feel normal - if it is very soft or goes down to the floor - you have an immediate, critical problem and need to get the car stopped safely and off the road as soon as possible. Shift to a lower gear to help slow the car, and use the parking brake, which is now the emergency brake, to help get your machine stopped.

ABS: This lamp is a warning that the anit-lock function of the braking system is not working. Unless the brake light is also illuminated, the brakes will still work, but have a qualified technician check the ABS for a problem.

This warning is part of the vehicle's on-board diagnostics (OBD) system, and indicates that the car's computer has detected an emissions-control issue, such as a faulty oxygen sensor. The results of ignoring this light could be catastrophic for your car.

Check Engine: This warning is part of the vehicle's on-board diagnostics (OBD) system, and indicated that the car's computer has detected an emissions-control issue, such as a faulty oxygen sensor. You may not notice any difference in the way the car sounds or drives, but if you ignore this light you could damage an expensive emissions control system - a clogged catalytic convertor is a common outcome. In some cases, you may void the warranty. On late-model cars, the check-engine light will illuminate if the gas cap is loose or missing. It needs to be tightened until it makes a clicking sound. If the cap was loose, it may take a few trips with a tight cap for the light to go off. If the cap is tight and light stays on, take the vehicle to a qualified repair shop, where a mechanic can plug a scanner into the OBD terminal and read a trouble code stored by the computer, which will pinpoint the problem.

Stability Control: When this light flashes, it's indicating that the electronic stability control (ESC, sometimes called vehicle stability assist, or VSA) is active. This means that you are likely driving around a corner too fast for the available traction, which may be compromised because of ice, snow or wet pavement. (The light should probably just say "Slow down!") An increasingly common feature on new cars and trucks, ESC will be required by federal regulations on most passenger vehicles by 2012. ESC monitors the vehicle's response to driver steering input, and then applies brakes on individual wheels to help the driver regain control in event of a spinout. The ESC may activate before you even feel the vehicle start to slide, but it's a warning that you need to proceed with caution.

Supplemental Restraint System: This light is alerting you to a problem with the supplemental restraints, which include the airbags, automatic seat-belt tensioners, driver's seat position sensor, the front passenger weight sensor and other items, depending on the vehicle. Consult your owner's manual for details, and see a dealer if you can't solve the issue on your own.

Maintenance: Not to be confused with the more urgent "Check Engine" light, this little wrench-shaped indicator is a reminder to take your vehicle in for scheduled maintenance. On some vehicles, there's an information screen that will tell you which maintenance is due, such as an oil change or air filter change. The dealer or service shop will reset this light when the service is complete.

Washer Level: This light signals you are low on windshield washer fluid. Get some soon. Check the owner's manual to find out where it goes. You can do this yourself if you can open the hood and find the blue cap. Here's a tip: If you are obviously out of washer fluid - the light is on and washer won't squirt - stop using the washers. On many systems, the electric pump is lubricated by the washer fluid, and if you run it dry, you'll ruin the pump.

Veteran moto-journalist and Wisconsin-native Charles Plueddeman has been driving and testing automobiles, motorcycles, boats, ATVs and snowmobiles for more than 20 years. He is a regular contributor to Boating Magazine and Outdoor Life, and his product evaluation articles have appeared in Popular Mechanics, Men's Journal AutoWorld, Playboy, Boats.com and many other national publications and Web sites.