My Check Engine Light Is On?

To schedule an inspection or to have your Gasoline /  Diesel Car / Truck check engine light diagnosed give A & A Complete Auto Repair Houston a call at (281)564-7782 or bring your car to 12160 Bissonnet St., Houston, TX 77099 and start saving money on your Car / Truck repairs today!

So, what does this mean? Is my car going to blow up! Is it going to be expensive to repair? Let's look at what the check engine light means and how it works.

All modern vehicles have a computer or ECM (Electronic Control Module) that controls the engine operation. The main purpose of the ECM is to keep the engine running at top efficiency with the lowest possible emissions. With today's strictest emission regulations it is not very easy to achieve - 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.

Today's cars have much more electronics than in early days - there is a large number of various sensors and other electronic devices that help the engine computer or ECM to monitor all vehicle emission-related systems. When the computer senses that there is a problem with any emission-related system or component, it stores the trouble code(s) in the memory and lights up the "Check Engine" or "Service Engine Soon" light to tell you that there is a problem and your car needs to be looked at.

The technician at the dealership or a garage then will hook up the scanner to the car's computer and retrieve the stored code(s). Then he will look it up in the service manual provided by the car manufacturer. The service manual contains the list of possible codes (about a few hundred) and describes what each code means and what needs to be tested. The code itself doesn't tell exactly what component is defective - it only says what engine parameter is out of normal range. The technician will have to perform further testing to pinpoint defective part.

So, Just hook my car up to the computer!

This is a very common statement made by customers with any type of problem from a check engine light on to the rattle in back seat! They all think there is a magic computer that tells the mechanic exactly what is wrong with the car!

This is far from the way it works. First of all, the handheld scanner only aids in diagnosing emission related and electrical concerns, including transmissions and body control functions.

Most repair shops will charge a diagnostic charge (usually $50 to $100 dollars) to scan test your cars computer system and check for codes in the system.

Some problems that will turn on the check engine light can be as simple as a loose gas cap or a major problem such as an engine misfire or a slipping transmission.

Many places sell code readers so you can scan your cars computer yourself, but by the time you spend the money for the scanner you could have it scanned by a professional and have it repaired at the same time. Most repair shops will not just replace a part because you tell them its bad, they will want to charge you to complete their own diagnosis. So unless you are a skilled mechanic I don't recommed wasting your money on a code reader.

Always have your vehicle checked anytime your check engine light comes on, becasue even minor problems can turn into major problems!

What makes the check engine light come on?

There are many different things that can cause your check engine light to come on. If your car's OBDII system is functioning properly, the CHECK ENGINE or SERVICE ENGINE SOON light should flash briefly when you turn your car's ignition key to the on position. After the brief flash, the light should go out and remain off while you are driving.

A glowing CHECK ENGINE or SERVICE ENGINE SOON light alerts you to problems in your car's onboard diagnostic system that should be checked out as soon as possible. There's no reason to panic and in many cases, you won't notice any difference in vehicle performance.

One of the most common problems with check engine lights on today's cars is a LOOSE or uninstalled gas cap! Yes, that's right your gas cap.

First, check the gas cap to make sure it was not left loose after refueling. Sometimes, this can trigger the light. Most OBDII-equipped vehicles have a gas cap that simply snaps in place, when turned to the right. Some early OBDII-equipped vehicles have threaded caps. On these, just turn the cap to the right until it begins to click. If the gas cap was loose, the light should go out after a few short trips.

If the gas cap is not the problem and the light remains on steady, have the system checked as soon as possible. A light that flashes requires more prompt attention, indicating a more severe condition that must be checked immediately to prevent damage to the catalytic converter. When you experience a flashing light, minimize driving at high speeds or under heavy loads. When scheduling service, make sure the shop that diagnoses your car has technicians who are properly trained and certified for OBDII diagnosis and repair.

Another common problem is filling your gas tank up with the key turned to the on position. This is very easy to do today with the introduction of the DVD player in alot of today's cars, trucks, and vans. Mom and Dad pull up to the gas station turn off the engine and then turn the key back on so the kids can watch their movie. This can, but not always turn the check engine light on, so be on the safe side and always fill up with the key in the off position.

Engine Control Sensors

Sensors measure a variety of operating parameters that help to reduce emissions and also serve functions for the engine, transmission and other systems. These sensors generally include the manifold air temperature sensor, coolant temperature sensor, manifold absolute pressure sensor, airflow sensor, throttle position sensor, vehicle speed sensor and oxygen sensors.

All of these sensors provide critical operating information to the vehicle's powertrain control module, the onboard computer that compares the signals from the sensors to programmed values. Based on the signals, the computer then issues commands to various output devices to control the engine and transmission, along with reducing emissions. 1996 and newer vehicles are equipped with second-generation onboard diagnostics (OBDII) systems that put special emphasis on sensor values and emissions.

Sensors do not require regular maintenance or adjustments. Regardless of what a specific sensor measures, all operate within a range of normal values. If a sensor provides a signal outside the normal range long enough, the powertrain control module will set a trouble code, which will usually trigger the SERVICE ENGINE SOON or CHECK ENGINE light.

To schedule an inspection or to have your check engine light diagnosed give A & A Complete Auto Repair Houston a call at (281)564-7782 or bring your car to 12160 Bissonnet St., Houston, TX 77099 and start saving mony on your car repairs today!


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