Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2002 Freightliner Sprinter 2500 L5-2.7L DSL TurboFACTORY OEM SERVICE PROCEDURE
Air Flow Meter/Sensor: Description and Operation
MANIFOLD AIR FLOW (MAF) SENSOR
DESCRIPTION
The Mass Air Flow (MAF) Sensor is located in the air intake port between the air filter and the turbo-charger. The MAF sensor uses semiconductor technology throughout, and is used to calculate the air mass flowing past it per time unit. This mass is important for determining the exhaust gas recirculation rate. The MAF sensor sends a corresponding signal to the ECM, which evaluates the signal to adjust the exhaust gas recirculation valve.
OPERATION
The ECM uses the mass air flow (MAF) sensor to measure air density. The temperature resistor located at the front of the MAF sensor measures the temperature of the inlet air. By varying the voltage, the electronic circuit regulates the temperature of the heating resistor in the rear so that it is 320° F (160° C) higher than the temperature of the intake air. The temperature at the heating resistor is measured by a sensor resistor in-between.
Because the incoming air has a cooling effect, the greater the amount of air that flows in, then the higher the voltage of the heating resistor. The heating resistor is therefore a measure of mass of air flowing past. If a temperature change occurs as a result of a increase or reduction of air flow, the ECM corrects the voltage at the heating resistor until the temperature difference is again achieved. This control voltage is use by the ECM as a unit measure for metered air mass.
DESCRIPTION
Mass Air Flow(MAF) Sensor:
The Mass Air Flow (MAF) Sensor is located in the air intake port between the air filter and the turbo-charger. The MAF sensor uses semiconductor technology throughout, and is used to calculate the air mass flowing past it per time unit. This mass is important for determining the exhaust gas recirculation rate. The MAF sensor sends a corresponding signal to the ECM, which evaluates the signal to adjust the exhaust gas recirculation valve.
OPERATION
The ECM uses the mass air flow (MAF) sensor to measure air density. The temperature resistor located at the front of the MAF sensor measures the temperature of the inlet air. By varying the voltage, the electronic circuit regulates the temperature of the heating resistor in the rear so that it is 320° F (160° C) higher than the temperature of the intake air. The temperature at the heating resistor is measured by a sensor resistor in-between.
Because the incoming air has a cooling effect, the greater the amount of air that flows in, then the higher the voltage of the heating resistor. The heating resistor is therefore a measure of mass of air flowing past. If a temperature change occurs as a result of a increase or reduction of air flow, the ECM corrects the voltage at the heating resistor until the temperature difference is again achieved. This control voltage is use by the ECM as a unit measure for metered air mass.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.