Re: Check Engine Light Fix (archive)

The way the check engine light (called a Malfunction Indicator Lamp=MIL in OBDII speak) works is that, in most cases, the DME needs to record TWO of the same faults in similiar conditions. When the fault first occurs it is recorded as a pending fault and the light is left off. If on the next trip (trip is definied as a cold start to warm up drive) the same fault occurs again the fault now becomes active. When this occurs the MIL is turned on and the DME records freeze frame data of the car at the time the second fault occured. The data can aid in the diagnostics of the fault.

Next you either bring your car in (or have the tools yourself) to read/clear that data and the light will go out OR you make X number (seems to vary depending upon fault) of 'clean' trips (no faults) and the DME will turn off the light on its own. It may or may not also clear the fault code(s) when this occurs as well. This is probably what happened in your case.

If you have a pending fault and make enough clean trips I believe the fault will be cleared as well.

There are a few faults that will light the MIL on the first fault. Pretty much anything that could result in catalytic converter damage will do it, and in that case the MIL will usually flash. If you ever get a flashing MIL stop the car immediately and have it towed to the dealer. Otherwise you risk buying a new cat. $$$$$$$$

Shawn

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