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Home >> Jaguar >> 2017 >> XJR L >> Repair and Diagnosis >> External Pages >> Different car >> Section 9 (Electronic Engine Controls - V8 N/A 5.0L Petrol -- XJ/X351) >> Description And Operation >> Electronic Engine Controls - System Operation And Component Description (G1772581) >> Component Description >> Mass Air Flow And Temperature Sensors

Mass Air Flow And Temperature Sensors

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The MAFT sensors allow the ECM to measure the mass flow and the temperature of the air flow into the engine. The mass air flow is measured with a hot film element in the sensor. The temperature of the air flow is measured with a NTC thermistor in the sensor. The mass air flow is used to determine the fuel quantity to be injected in order to maintain the target air/fuel mixture required for correct operation of the engine and the catalytic converters.

There are two MAFT sensors installed, one in each air cleaner outlet duct. Each MAFT sensor is secured with two screws and sealed with an O-ring. On each MAFT sensor, a five pin electrical connector provides the interface with the engine harness.

If the hot film element signal fails the ECM invokes a software backup strategy to calculate the mass air flow from other inputs. Closed loop fuel control, closed loop idle speed control and evaporative emissions control are discontinued. The engine will suffer from poor starting, poor throttle response and, if the failure occurs while driving, the engine speed may dip and surging may occur before recovering.

If the NTC thermistor signal fails the ECM adopts a default value of 25 °C (77 °F) for the intake air temperature.

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