On Again, Off Again

No I'm not talking about that relationship you're in, I'm talking about the “Check Engine, or “Service Engine Soon” light in the dash of your car. I know it was on a couple of months ago, but it has reared its ugly head again.

So you bring it to your local repair shop thinking that it’s the same problem again, and you’re angry. “Why is this light back on, you just fixed it!”

Your service manager reassures you in that calm voice that “we’ll look into it and let you know what’s going on.”

What you don’t know is that the check engine light monitors many things.

  • Misfires, which includes the spark plugs and the ignition coils.
  • Fuel mixture, which includes the fuel injectors, the intake manifold, the crankcase ventilation system, and the oxygen sensors.
  • Evaporative control, which includes the fuel cap, the fuel tank, vapor recovery tank, the evaporative testing pump, and the purge control valve.
  • The exhaust system, which includes the oxygen sensors, catalytic converters, and for diesels, the diesel emissions fluid system.
  • The Camshaft timing system, which includes the camshaft position sensors, and the variable valve timing system.
  • And various sensors, like the crankshaft position sensor, air mass sensor, intake temperature sensor, coolant temp sensor, and a few more that I might have not listed.

As you now might understand that there are many different things that can cause the light to come on, and it’s not always the same thing that is causing your issue.

There is no way of knowing what is causing the warning to come on until you use the special equipment to read the codes set in the engine control module or ECM. There are code readers you can buy at your local auto parts store or tool supplier, but they are only going to give you generic codes. The special equipment that your automotive specialists uses, reads the manufacturers specific codes, and includes the trouble shooting tools needed to properly test and pinpoint the problem causing the light to come on.

Each time the car comes in with the check engine light on; it has to be treated as a new problem. It is highly unusual that the light will come back for the same reason. Occasionally the technician will make a mistake in the troubleshooting, or a part will be defective, but that is very rare, especially with the quality of the test equipment and parts being used these days.

What I’m trying to say here is that there are too many things that can cause the check engine light to come on. As a professional I wouldn’t jump to conclusions on what is the cause. I’d let the facts answer that question for me. Have a professional run the codes and do the trouble shooting to determine the fault. The facts don’t lie. We have the correct equipment to test and troubleshoot your car. Give us a call and make an appointment.

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