The Dreaded “Check Engine” Light
Uh oh. There’s that “Check Engine” light. Or, maybe your car has a “Service Engine Soon” light illuminated. Sounds ominous, doesn’t it. Well, there’s a reason. Let’s discuss what it means when you get a “Check Engine” light and what you need to do about it.
Why the Light Turns On?
All modern vehicles have a computer or ECM (Electronic Control Module) that controls the engine operation. It also performs onboard diagnostics which is referred to as OBDII. The main purpose of this module is to keep the engine running at top efficiency with the lowest possible emissions. Today's strict emission regulations are not very easy to achieve - to keep it in compliance, the engine needs to be constantly and precisely adjusted according to various conditions such as speed, load, engine temperature, gasoline quality, ambient air temperature, road conditions, etc.
The best thing about the “Check Engine” light is that it often detects little problems before they become big, expensive problems. Not every problem gives you obvious indications like you get with such things as hard starting, rough running, stalling, etc. That’s why it is very important not to ignore this little light. The “Check Engine” light alerts you to problems like poor fuel mileage, reduced performance or excessive exhaust emissions.
What if My “Check Engine” Light is On?
The simplest way to handle this situation is to visit Shade Tree Garage where we will read the memory to see what fault the computer is reporting. Sometimes it is just a loose gas cap and other times further testing is required. We have all the equipment and information needed to determine and correct the problem. In the event the problem is something covered under the manufacturer’s warranty, we will notify you so you can have it repaired at your dealer free of charge.
“Service Engine Soon” Light. But How Soon?
Since the "Service Engine Soon" Light is primarily an emissions monitor there is no need to panic. Unlike the overheat or charging system red warning lights that require an immediate shutdown of the engine, this one is advisory and is yellow or orange. Even though it doesn’t indicate the car is likely to quit, it is calling out for help. Think of the "Service Engine Soon" lamp as if it were the glowing tip of a cigarette. Your car is polluting as well as performing below its design potential. Plus, the average cigarette only burns for seven minutes and it is out, the car meanwhile will run for hours, days, weeks and even months.
My guy turned the light off and it came back on a week later. How come?
The onboard diagnostic (OBD) system is constantly performing a series of “self-tests” to determine if everything is working as designed and your car is running clean. When a failure is detected, the system will compensate if possible and many of these tests are temporarily turned off. This means the repair process can often lead down a trail of multiple problems. This is especially true if you have been driving with the check engine light on for several days.
Once repairs are completed, the OBD system re-starts its series of self-tests. Some of the self-tests require specific conditions to occur before they can be run. For example, one requires the engine to not be started for at least eight hours. Another requires the vehicle be driven for several minutes above 50 mph. This is why the testing phase is so critical to effecting a proper repair the first time.
It is important to discuss any concerns you may have.
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