Let’s be honest here: most of us are guilty of not following a manufacturer’s maintenance schedule to the letter. Sure, we change the oil and (probably) check the air in the tires, but how many of us rotate tires at the exact recommended intervals or change automatic transmission fluid on the maintenance book schedule? Despite this, today’s cars are more reliable that at any other time in history. I haven’t been stranded by the roadside since my Ford Taurus’ fuel pump died in 1990, and I drive a lot of cars from a lot of different manufacturers each year. Most cars today are smart enough to tell you when something is wrong, via idiot lights or flashing trouble codes, All warning lights denote a problem, but some are more serious than others. Below are five that get my immediate attention.
Oil Pressure Warning Light
If you see this light come on, stop the car as soon as it’s safe to do so. Driving it, even for a few miles, is risking expensive (and possibly permanent) engine damage, ranging from a heat-seized engine through broken connecting rods. Even new cars can lose oil pressure due to manufacturing defects, so don’t think you can ignore the light if you just left the dealer lot in a new car. If you see the light come on, pull over and check your oil immediately; if there’s none on the dipstick, add oil to the full mark before you attempt to drive the car. If you’re mechanically inclined, you can try to diagnose the problem yourself (lots of oil on the ground = bad sign) if you’re not, get your car to a mechanic ASAP.
Tire Pressure Warning Light
It never ceases to amaze me how many people drive on near-flat tires; if you can’t feel the difference between a tire with 5 psi and a tire with 32 psi, you shouldn’t be driving in the first place. To make things easy, however, modern cars (built after 2007) come equipped with tire pressure monitoring systems that give you a warning when a tire has low pressure. Generally, this is due to a change in temperature (lower temps = lower pressure), but it could also be due to a nail in your tire. Better to find this in your driveway than to have the tire go completely flat on the road. Changing tires on the side of a busy interstate highway is not my idea of a good time.
Check Engine Light
A check engine light by itself can indicate dozens of different problems, and most of them aren’t serious. A loose gas cap, for example, will trigger the light, as will a bad oxygen sensor in the exhaust system. Modern cars generally have a “limp home” setting that allows you to drive even if there’s a sensor problem, but with reduced power (or higher fuel consumption). If I get a check engine light, the first thing I do is check the gas cap to make sure it’s tight. If that doesn’t solve the problem, I’ll throw a code reader on the car to see what’s wrong. I wouldn’t stop driving a car with a check engine light on, but I would get it looked at ASAP.
Temperature Warning Light
Modern cars go through some pretty serious testing prior to launch, including things like towing a trailer on an uphill grade in summer with the A/C set to “Max”. Unlike years past, you no longer have to turn off the A/C when in stop and go traffic on a hot day, but mechanical problems (like a stuck thermostat or a clogged radiator) can still cause overheating. If the light comes on, pull over immediately and pop the hood if it’s safe to do so. If you see steam pouring from under your hood, be VERY careful. It may be a good idea to just crack the hood open until the system pressure decreases a bit, because steam burns to the face aren’t particularly enjoyable. Never, under any circumstances, try to remove the radiator cap; instead, add water to the coolant reservoir bottle beside the radiator. If your car is old and this is a re-occurring problem, get it checked out when your budget allows. If your car is new and under warranty, get it towed back to the dealer and let them worry about it.
Brake Warning Light
Todays cars have complex braking systems that split the bias front to rear (and possibly side to side), measure individual wheel speed and even brake without your knowledge to distribute torque to wheels with traction. When something goes wrong, the problem is no longer as simple as checking the fluid level in your master cylinder (although that’s a good place to start). As brake pads wear, the fluid level in the master cylinder decreases, and a low fluid level probably means you need new brake pads. It may also mean you’ve got a dangerous brake fluid leak, so any brake system warning light should be checked by a mechanic as soon as possible.