Used Car Buying - Exhaust & Emissions

Emissions and the check engine light

The light on the dashboard of most newer cars that advises to check the engine is directly tied to the exhaust systems of the car. There are a series of sensors on newer generation cars which measure the output of the engine looking for variances or failures in the tolerance of unburned and harmful emissions. The presence, or elevated levels of these emissions are an indication that the engine is not running optimally.





A check engine light on the dashboard of a used car will most often diagnose back to a fault in the emissions testing sensors such as a failed oxygen sensor. Our mechanic advises us that the check engine light can actually activate for a number of very minor reasons such as a loose or leaking gas cap on your fuel tank.

The car computer will tell you exactly what is wrong

A check engine light does not necessarily mean that major work is required to the car. A mechanic shop can perform a very easy and non invasive scope of the computer on board the car. If you are concerned about a check engine light problem you can quickly and easily find out what codes the computer is outputting by using an electronic scope that you plug right into your car.





You could even purchase a scope so that you can read the codes outputted by the car computer yourself - it literally plugs right into the dash! Once you know the code that the computer is flashing you can reference the booklet that goes with the scope and look up why the check engine light is on.


A check engine light may deter a lot of people from buying a used car, and may devalue the car in the eyes of the seller also. It would be beneficial to you if you could know that the check engine light is on simply because the gas cap is loose.


Proceed now to the section covering the inspection of the drivetrain of the car.