Engine Light On?

What the Light Means

The “check engine” light is part of your car’s so-called onboard diagnostics (OBD) system. Since the 1980s, computers increasingly have controlled and monitored vehicle performance, regulating such variables as engine speed (RPM), fuel mixture, and ignition timing. In some cars, the computer also tells the automatic transmission when to shift.

When it finds a problem in the electronic-control system that it can’t correct, the computer turns on a yellow warning indicator that’s labeled “check engine,” “service engine soon” or “check powertrain.” Or the light may be nothing more than a picture of an engine, known as the International Check Engine Symbol, perhaps with the word “Check.” In addition to turning on the light, the computer stores a “trouble code” in its memory that identifies the source of the problem, such as a malfunctioning sensor or a misfiring engine. The code can be read with an electronic scan tool or a diagnostic computer.

Manufacturers originally used the OBD system to help technicians pinpoint and troubleshoot malfunctions. But the systems now are required under federal laws governing automotive emissions. Although larger trucks have been exempt from the requirement, that quickly is changing.

“The ‘check engine’ light is reserved only for powertrain problems that could have an impact on the emissions systems,” says John Van Gilder, General Motors’ lead OBD development engineer.

Exactly what the OBD system looks for depends on the make, model and year. The original systems varied widely in their capabilities. Some did little more than check whether the various electronic sensors and actuators were hooked up and working.

That changed by 1996, when, under OBD II regulations, carmakers were required to install a much more sophisticated system that essentially acts like a built-in state emissions testing station. The computer monitors and adjusts dozens of components and processes. For example, it continually samples exhaust emissions as they come out of the engine and again when they leave the catalytic converter, a device that removes carbon monoxide and hydrocarbon pollutants from the exhaust. The system also monitors your car’s fuel system to ensure that gasoline vapors are not escaping into the atmosphere through a leak or even a loose or missing gas cap. In most cases, if a problem occurs, the computer will wait to see if it corrects itself before turning on the light. Modern OBD II systems are so thorough that state testing centers increasingly are checking for any stored trouble codes and foregoing the traditional tailpipe emissions test.

WHAT HAPPENS IF YOUR LIGHT COMES ON?

If your light comes on we have the latest Bosch KTS Diagnostic Equipment, this equipment can check all your onboard computers for faults and with our Bosch trained technician “Adam Williams” you can rest assured your vehicle is in the best hands. For help, advise or to make a booking give us a call on 01736 755684 or email us: [email protected]

 

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