What the heck does that mean? Is it just a ploy to get me to spend money? NO NO NO. The check engine light is a measurement device that monitors many different functions of your Subaru while you are driving. There are many different sensors and sending units throughout your Subaru that continually feed information to your Subaru’s computer. When the check engine light comes on this means that somewhere in the system one of those sensors or sending units has detected a signal either above or below correct parameters.
The most common check engine light is the old “forgot to tighten the gas cap” signal. Either you did not replace the cap after filling the tank, or you did not give it the 5 clicks needed to reseal the pressurized fuel system. So here is a free tip, if the check engine light comes on shortly after refueling (it will take a while to come on), stop and make sure your caps is tight by 5 clicks then continue to drive your Subaru. You may need some 20 cycles, this means up to 20 starts and shut downs. If it is the gas cap was not tight enough, then it should now go out. There are other possible problems with the gas cap, after a while the seal on the gas cap will wear out and you may need to replace the cap itself.
Now there are many other reasons for the check engine light to suddenly turn on. It may be something as simple as a temperature sending unit, an electric fan switch, or the more costly code 420 catalytic converter below threshold. Most cases it is a simple sensor or sending unit, easily and quickly replaced. In some cases such as a cylinder misfire, it can be a bit more complex. Possible plug wires, leaking plug well seals to stop the spark plug from firing, none of these items are catastrophic and quickly rectified.
The best thing for you to do when a check engine light comes on while driving your Subaru is to check that pesky gas cap, and if that is not the culprit get the light checked. It is never a good idea to just continue to drive with the light on. For example if it is a fuel trim code your engine may be running lean (possibly burning vales, or scoring cylinder walls and ruining your rings). If it is running rich you take the chance of destroying your catalytic converter, another very expensive repair.
If you continue to drive your Subaru with the check engine light on, the system may go into limp mode and then your Subaru may be hard starting, a loss of power, and lose fuel economy. There is a reason Subaru installed the check engine light and it is in your best interest to pay attention to what its telling you. As a general rule it is less expensive to have the check engine light code repairs when it first comes on. Continued driving may cause very expensive damage to your Subaru.
