MAF Sensors (AE06)

What is the primary function of a Mass Airflow (MAF) sensor?

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How does the ECU utilise the data from the MAF sensor?

• To adjust the ignition timing.

• To control the operation of the EGR valve.

• To calculate the correct amount of fuel to inject.

• To monitor the coolant temperature.

Describe the construction and operation of a hot wire MAF sensor.

• It uses a bimetallic strip that bends in response to airflow.

• It uses a small turbine that spins at a speed proportional to airflow.

• It uses a heated wire that is cooled by the airflow, and the current needed to maintain its temperature is measured.

• It uses a pressure sensor to measure the difference in pressure across a restriction.

What is the typical diameter of the wire in a hot wire MAF sensor?

(a)  

• 0.5 mm
• 0.1 mm

• 1.0 mm

• 0.25 mm

Explain how the electronic control circuit responds when air flows over the hot wire.

• It increases the voltage across the wire.

• It decreases the resistance of the wire.

• It increases the current flowing through the wire.

• It reduces the current flowing through the wire.

What is the purpose of the burn-off function in some MAF sensors?

• To increase the sensitivity of the sensor.

• To measure the oxygen content of the air.

• To remove contaminants that have accumulated on the sensing element.

• To calibrate the sensor.

How does a hot film sensor differ from a hot wire sensor?

• A hot film sensor is more sensitive than a hot wire sensor.

• A hot film sensor is less expensive to manufacture than a hot wire sensor.

• A hot film sensor uses a thin film of platinum deposited on a ceramic substrate, while a hot wire sensor uses a thin wire.

• A hot film sensor is used in diesel engines, while a hot wire sensor is used in gasoline engines.

List some symptoms of a defective MAF sensor.

• Poor fuel economy, hesitation on acceleration, rough idling, stalling.

• Overheating, loss of coolant, white smoke from the exhaust.

• Excessive oil consumption, blue smoke from the exhaust.

• Brake fluid leak, spongy brake pedal.

What are some typical generic EOBD diagnostic trouble codes related to MAF sensors?

(a)  

• P0100, P0101, P0102, P0103, P0104
• P0300, P0301, P0302, P0303, P0304

• P0400, P0401, P0402, P0403, P0404

• P0171, P0172, P0174, P0175

Outline the steps involved in a typical MAF sensor inspection procedure.

• Visually inspect for damage or contamination, check the electrical connector and wiring, use a scan tool to check for codes and data.

• Remove the spark plugs and inspect for wear or damage.

• Check the engine oil level and condition.

• Check the tire pressure and tread depth.