Actron 9640A manual Monitor, Mpfi or MFI, NOx, O2S, Sensor

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Glossary

KOER:

Key On — Engine Running.

LCD:

Liquid Crystal Display.

LT:

Long Term fuel trim.

M/T:

Manual transmission or manual transaxle.

MAF:

Mass Air Flow Sensor. Measures the amount and density of air entering the engine and sends a frequency or voltage signal to the PCM. The PCM uses this signal in its fuel delivery calculations.

MAP:

Manifold Absolute Pressure Sensor. Measures intake manifold vacuum or pressure and sends a frequency or voltage signal (depending on sensor type) to the PCM. This gives the PCM information on engine load for control of fuel delivery, spark advance, and EGR flow.

MAT:

Manifold Air Temperature sensor. A resistance sensor in the intake manifold that sends a voltage signal to the PCM indicating the temperature of the incoming air. The PCM uses this signal for fuel delivery calculations.

MIL:

Malfunction Indicator Lamp. The MIL is most commonly known as the “Check Engine” or “Service Engine Soon” light. A required on-board indicator to alert the driver of an emission-related malfunction.

Monitor:

Atest performed by the on-board computer to verify proper operation of emission related systems or components.

MPFI or MFI:

Multi-Port Fuel Injection. MPFI is a fuel injection system using one (or more) injector(s) for each cylinder. The injectors are mounted in the intake manifold, and fired in groups rather than individually.

NOx:

Oxides of Nitrogen. A pollutant. The EGR system injects exhaust gases into the intake manifold to reduce these gases at the tailpipe.

O2S:
Oxygen Sensor. Generates a voltage of 0.6 to 1.1 volts when the exhaust gas is rich (low
oxygen content). The voltage changes to 0.4 volts or less when the exhaust gas is lean
(high oxygen content). This sensor only operates after it reaches a temperature of
approximately 349×C (660×F). O2 sensors are usually found both upstream and down-
stream of the catalytic converter. The PCM uses these sensors to fine tune the air-fuel
ratio and to monitor the efficiency of the catalytic converter. See Bank 1, Bank 2, Sensor
	B
1, Sensor 2.
OBD II:
On-Board Diagnostics, Second Generation. OBD II is a U.S. Government-mandated
standard requiring all cars and light trucks to have a common data connector, connector
location, communication protocol, DTCs and code definitions. OBD II first appeared on
vehicles in late 1994, and is required to be present on all cars sold in the US after January
1, 1996.

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