What is your car telling you?

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Updated: 10/08/2012 4:33 pm Published: 10/05/2012 4:01 pm

Every time you start your vehicle, a multitude of symbols light up on your dash briefly, then go out. Or at least most of them should go out. Troy Cox of Cecil and Sons Discount Tires stopped by GDGC to discuss the most important warning lights, what they’re trying to tell you, and their priority. Please note that most, if not all, will light briefly when you start your vehicle as each goes through a short self-diagnostic. Typically, they’ll go dark in seconds and are only a concern if they stay lit or come on suddenly while you’re driving.

Red warning lights: These are the “stop” lights, the ones telling you to stop immediately and get whatever issue they represent checked. Some common examples are the oil pressure warning; typically when lit it is a red light marked “oil” or an icon that looks like an oil can. That light tells you the oil pressure in your engine is dangerously low and continuing to operate your vehicle could cause serious damage. Stop immediately and check your oil level; if it’s low add enough to get back to the safe range before restarting your car. If you’ve got the proper oil level on the dipstick and the light is on anyway, call a tow truck and have it towed to a service facility as you’ve likely got a mechanical problem and continued operation could further damage the motor.

Another example is the red “brake” light. It comes on when the parking brake is engaged to help you remember to release it and should go out if the parking brake is not engaged. It also comes on as an indication of low fluid level in your master cylinder; if the master cylinder fluid level is low then top it off with the correct type of brake fluid which is typically marked on the cap. Low pressure in the system can also cause the red brake warning to light; this could be anything from air getting into the system to a fluid leak—the important thing here is inadequate pressure or brake fluid leakage can prevent your vehicle from stopping properly. Lose enough fluid, and it may not stop at all.

Temperature warning lights, whether a thermometer icon or a simple light, are telling you your vehicle is overheating, and should never be ignored. As with the oil pressure warning light, this is a “stop immediately” issue—but it is not something you can actually check immediately. Certainly you can pop the hood and visually check the translucent coolant reservoir if you don’t see steam, smoke, or liquid coming out around the hood or under the car. If that reservoir is empty then you know you’ve lost your coolant, but never, ever try to open a pressure cap on your cooling system while the system is hot. Your car’s cooling system is under pressure: anywhere from 10 to 16 psi of pressure when operating normally. If you try to open the cap on an overheating vehicle you’re likely to spray scalding hot coolant everywhere…including on yourself. So you must wait until the system has cooled down to prevent potential injury.

The other red “stop” light is your charging system warning, which can be a simple “temp” logo and red light or an icon that looks like a car battery. This light is telling you there’s a problem with your charging system that recharges your car’s battery and provides the power for everything from door locks and windows to the spark plugs and the computer that fires them. You can run for a limited time on your battery’s stored power only; by turning off all unnecessary electrical accessories like lights or radio you can extend that time somewhat. However, when that battery falls below a certain voltage your car will stop running. Better to stop at the first practical place to see what’s going on with your charging system rather than continuing on blindly as you’ve no way of knowing after that warning light comes on when your car may stop running.

Yellow warning lights: These are the “caution” lights indicating service may be needed; you may not have to stop immediately but you need to be aware of what’s going on if you are going to continue. The most common one seen when driving is the low tire icon--which in my opinion should be a “red”. Government sources estimate that underinflated tires are a contributing factor in automotive crashes causing approximately 600 deaths and 30,000 injuries each year. The low tire icon is yellow or amber and looks like a “U” with an exclamation point in it. Some tire pressure monitor systems will tell you each tire’s pressure so you’ll know which is low; others require you to check all your tires to find out which is low—either way you need to check this out as quickly as possible. Operating a tire with less air pressure than it needs for the load it is carrying results in rapid heat buildup which can ruin a tire in a very short distance or even cause it to fail catastrophically with serious effects on the vehicle’s handling and stability.

“Check engine” or “service engine soon” lights most commonly indicate your car’s onboard computer has received a diagnostic trouble code (DTC) from one of its sensors or is having communication difficulties between modules. Normally this means a trip to someone with a scan tool to read those codes and try to interpret what the vehicle is reporting. The most common code we see are simple things like not properly tightening the gas cap after filling up. The fuel system “sees” that loose cap as an evaporative emissions system fault and reports it. The fix is either tightening up the cap, or replacing it if the rubber seal on it is damaged or broken. Other codes are more involved and can involve two or even three interrelated systems needing to be checked to determine where the fault lies. Typically you can drive a vehicle with this light on for quite some time, although usually at the cost of poorer fuel economy and performance. If the problem is severe enough, your onboard computer can even go into “limp” mode where you can operate, but with very limited power, ideally just long enough to get into a service facility.

In addition to the red brake warning light discussed earlier, you also will have a yellow “ABS” or “antilock braking system” warning light. This reports on the sensors, electronic valves, pump, and computer module that activate to pump your brakes and help prevent a skid during emergency braking. If this light comes on, typically it’s telling you a fault has been detected in the antilock system and it’s shut itself down. You still have your regular brakes, just not ABS capabilities. About the only simple thing that can cause the “ABS” or “antilock” warning to light is low brake fluid levels in the master cylinder which will normally cause the red “brake” warning light to come on as well. If the fluid level did not get low enough to allow air to be sucked into the brake system then adding the correct fluid should extinguish both lights—but your fluid level should not change suddenly; if it does, then have the brake system checked for fluid leaks. Anything else will require the appropriate scan tool to try and pinpoint the fault.

The airbag warning light, if it stays lit past the normal “self check” time, is telling you there’s a fault in that system. Normally that means the computer has shut down that system and you won’t have an airbag to protect you in case of a crash. Occasionally, the system fault does not disarm the airbag and there are scattered reports of airbags going off unexpectedly…with a detrimental effect on the driver’s vision and control. Again, this one needs the appropriate scan tools to talk with the computer controlling that safety system and shouldn’t be put off as airbags going off unexpectedly, or not going off properly in a crash, are serious safety issues.

There are other fairly self-explanatory lights, of course, ranging from the “cruise” to “door ajar” to “change oil”. Some are specific to engine type; you’ll find a “glow plug” warning light on diesel engine vehicles telling you to wait to try and start until the glow plugs have warmed up. “Traction control” or electronic stability control “ESP” lights will often come on to tell you those systems have activated; as with the others we’d discussed it’s when they stay on that a problem is indicated. As always, your best resource is your owner’s manual as they will typically have a photo representation of your dash with every gauge, dial, or warning light clearly numbered and identified.

Cooper’s “Take the Money and Ride” rebate is going on thru November 6, 2012, and the purchase of a qualifying set of Cooper tires could qualify you for an up to $75 rebate by mail from Cooper Tire and Rubber.

Cecil and Sons Discount Tires is family owned and operated since 1973; three generations of our family serving, in many cases, third and fourth generations of our customer’s families. Cecil and Sons has tires, custom wheels, alignment and suspension repair, brakes, preventative maintenance and light line mechanical service.

Cecil and Sons Discount Tires
204 East Morrow Road
Sand Springs, OK

4002 South St Hwy 97
Sand Springs, OK


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