In a previous post we discussed the Check Engine light and the associated electronics that are attached to that light. Basically, the modern automobile engine is controlled by a central computer system that monitors and regulates fuel, ignition and in some cars cam timing to make your engine as powerful, fuel efficient and clean burning as possible. And this type of central computerization makes your modern car smooth and efficient to drive.
We also talked about how the Check Engine light is a warning signal that there is a problem with one of the many systems of the car’s engine. When the light comes on, the informed owner should not panic and run blindly to a service facility, but rather he should first look at the car’s central computer’s display to see exactly what the problem is. On many cars, the central computer will display a binary number code that will give the exact nature of the problem. Your owner’s manual or a service manual for your car (available for about $10 at your local auto parts store) may contain the information to decode the computer’s code. On some cars, a relatively inexpensive dongle available at specialized parts and tool stores plugs into the car’s central computer to read the information. And in the case of a few models, the information can only be read by an expensive piece of equipment that is only available at the dealership or specialized service center.
Once the information has been decoded, the warning signal coming from the engine’s central computer must be cleared and the Check Engine light extinguished. The Dealership will charge you a lot of money to turn this light off, on BMW’s it requires a special tool to reset the computer (guaranteeing that you will have to visit the dealer’s service department). Considering that the dealership makes their most money not from selling cars but from insuring that their service bays are filled with customer’s cars.
The secret that the dealership does not want you to know is that the signal from the Check Engine light can be a false alarm. Yes! It is true; a car’s central computer can make a mistake. Ask Dave the Astronaut from 2001: A Space Odyssey about a vehicle’s central computer making a mistake, it can happen. To test if your Check Engine light is a mistake or not, all you need to do is to reset the computer (sort of like rebooting a Windows computer when it gets stupid). Again, in your Owner’s manual there may be the information needed to reboot or reset your car’s central computer. If not, the best way for the At Home Mechanic to reset the computer is to simply remove electrical power to the central processor and then restore power to it. In most cases, it is as simple as removing and replacing the fuse that supplies power to the computer. Check your Owner’s manual for the fuse location.
The Check Engine coming on is not a death knell for your car’s engine, most times when it comes on it is warning of a relatively minor fault or in some cases not fault at all. Before you get excited when that light comes on, take some time to read the information that comes in your owner’s manual to be an informed and empowered car owner before you take it to the service center.