Engine Light Glossary

DTC (Diagnostic Trouble Code)

This is the alpha-numeric code that will help you define the malfunction of your engine systems

OBD (On Board Diagnostics)

This is the name given to the government related diagnostics system for all vehicles from 1996 to present day

ECM (Engine Control Module)

This can also be referred to as the PCM, or Power train Control Module. This is the computer that controls the electrical functions of your engine and this is also the module that turns on the check engine light

CEL (Check Engine Light)

This can also appear as "Service Engine Soon" either way it's worded, this is the indicator on your dash to tell you something has malfunctioned. It all depends on the make of your vehicle as to which will show up.

RPM (Rotations Per Minute)

The RPM gauge on your dash tells you how fast your engine is spinning. For engine speed it's RPMx1000. There are other components that will have the RPM measured, but the only one you can see without a scanner is engine RPM.

MAP sensor (Manifold Absolute Pressure sensor)

This sensor tells your ECM important information about atmospheric pressure outside of the engine, the air pressure inside of your intake manifold, and the difference between the two

MAF sensor (Mass Air Flow sensor)

This sensor tells the ECM how much air is entering your engine. The ECM uses this to info to calculate several different values for fuel delivery

TPS (Throttle Position Sensor)

This sensor tells the ECM how far you're pressing the gas pedal. This info is important to the transmission as well for shift patterns

ECT (Engine Coolant Temperature sensor)

This does exactly what it sounds like, it tells the ECM how hot the engine coolant is. The ECM uses for fuel delivery strategies to help maintain the best fuel economy

IAC (Idle Air Control valve)

This valve is used for maintaining a set, constant, engine speed when the vehicle is idling

CKP (Crankshaft Position sensor)

The ECM uses this to electronically calculate the exact position of the crankshaft. It does this to know where each cylinder is in the 4 stroke combustion process: Intake, Compression, Power, Exhaust

CMP (Camshaft Position sensor)

The ECM uses this info to electronically calculate the exact position of the camshaft. It does this to determine things like fuel injector sequence and ignition coil firing sequence. There may be more than one of these sensors, depending on how many camshafts your engine has

EGR (Exhaust Gas Recirculation valve)

This valve is used to route some of the exhaust gasses back to the intake manifold to be run through the combustion process again. This is to cool the temperature of the combustion chamber and to help your vehicle have cleaner emissions