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J&W Auto Repair

AUTOMOTIVE: Check engine light

By Wyatt Nettles

What is a “Check Engine” light?

The check engine light is to warn the driver of some kind of computer system problem.  The computer system consists of a module that collects information from sensors on the engine.  This is called an ECM – Engine Control Module.  A module can also collect information from the transmission.  This is called a PCM – Powertrain Control Module.

The information comes from different sensors.  These sensors tell the module what conditions are in the engine.  You have temperature sensors (CTS, ACTS); manifold air pressure sensor (MAP); oxygen sensor (O2 sensor); mass air flow sensor (MAF); throttle position sensor (TPS); crankshaft position sensor (CPS); and camshaft sensor (CS).  On the transmission, you have speed sensors (Input and Output).

The module collects all of this information and calculates it and sends out commands.  These commands are sent to the timing controls in the ignition system, fuel controls on the fuel system and shift controls to the transmission.  The ignition system controls spark and spark timing.  Spark is needed to burn air/fuel mixture.  Without spark the engine will not run, but the timing of the spark is important for power and emissions and fuel economy.  Also, fuel delivery is important for the same.  On most cars, fuel is delivered by injectors into the intake manifold.  On newer cars, the injectors put fuel into cylinders.  This is called Direct Injection.  Timing and the amount of fuel is critical to engine performance.  Together these systems help fuel economy, power and emissions.

So when the “Check Engine” light comes on, it can mean a lot of things, and you should have it checked out.  Have it checked out by a professional that can fix the problem, not just replace parts.