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General Terms to Help Newbees


Guest 88atta

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Found this on my travels through the internet. Thought it might be helpful as it simplifies many of the common terms used on the forum and translates them in laymen's language.

GM EFI Tuning

So you want to know what is going on inside the brain of your OBD I GM vehicle?

Let's go over some of the terminology used in some of the more common scanning software and scanners.

BLM-Block Learn mode. This is often referred to as the “long term” fuel trims. Long term in computer speak is a few seconds.

INT-Integrator. Also called the “short term” fuel trims, as in a second or two.

IAC-Idle Air Control. This is usually a small stepper motor that moves a pintle in a seat to regulate airflow at idle and is expressed in steps, usually 0-255.

ECM -Engine Control Module. This is the computer that runs the engine systems, gathers information and makes corrections to the systems as needed.

TPS-Throttle Position Sensor. This is a potentiometer that tells the ECM how far open the throttle blades are. Its readings are in percentage and voltage (0-5 vdc)

MAF-Mass Air Flow (sensor). This sensor tells the ECM how much air is entering the throttle body. The most common MAF’s are the “heated wire” type.

MAP-Manifold Absolute Pressure (sensor). This sensor is used in place of a MAF on some systems; it measures pressure within the intake manifold and sends the readings to the ECM for fueling calculations.

PCM-Powertrain Control Module. This serves the same function as the ECM, except that it also controls the transmissions in vehicles equipped with “electronic” transmissions.

MAT-Manifold Air Temperature (sensor). This device measures the temperature of the air in the inlet tract.

CTS-Coolant Temperature Sensor. Measures the temperature of the engine coolant and sends that information to the ECM for fuel and spark calculations.

CSI-Cold Start Injector. This device was used mainly on the 1985-1988 GM TPI engines. It supplied extra fuel for cold starting of the engine.

EGR-Exhaust Gas Recirculation (valve). Primarily used as an emission control it has a major benefit of cooling the combustion chambers, which helps control detonation.

O2-Commonly used to refer to the oxygen sensor. This sensor “reads” the oxygen content of the exhaust gasses and reports that to the ECM.

VSS-Vehicle Speed Sensor. This sensor tells the ECM how fast the vehicle is moving.

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Guest Double M

Very thoughfull and much apprciated. If only everyone would be so, many of us newbies would be able to get much more info from this forum. We humans in America speak mostly english, but it seems that some prefer to talk or type as if they are texting and speak in abreviations. While it might make you seem very learned to the others that speak in "Alpha" those of us looking for help only get a string of letters or cryptic codes and first have to figure that out before even figuring out our problem in the first place.... IMHO...

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