chain JAGUAR XF 2009 1.G AJ133 5.0L Engine Manual

Technical Training
NP10-V8JLR: AJ133 5.0-Liter DFI V8 Engine 04/14/2009
3-17
Engine Management System

Mass Air Flow Sensor

MASS AIR FLOW SENSOR
Mass air flow is determined by the cooling effect of
intake air passing over a ‘hot film’ element contained
within the device. The higher the air flow the greater the
cooling effect and the lower the electrical resistance of
the ‘hot film’ element. The ECM then uses this analog
signal from the mass air flow (MAF) sensor to calculate
the air mass flowing into the engine.
The measured air mass flow is used in determining the
fuel quantity to be injected in order to maintain the sto-
ichiometric air/fuel mixture required for correct opera-
tion of the engine and exhaust catalysts. Should the
device fail, there is a software backup strategy that will
be activated once a fault has been logged.
The intake air temperature (IAT) sensor is integrated into
the MAF sensor. The IAT sensor is an NTC thermistor,
meaning that the sensor resistance decreases as the sen-
sor temperature increases.
The sensor forms part of a voltage divider chain with an
additional resistor in the ECM. The voltage from this device
changes as the sensor resistance changes, thus relating the
air temperature to the voltage measured by the ECM.
Because the engine requires a twin air intake induction
system, there are two MAF sensors per vehicle.
Safety Precautions CAUTIONS:
• Component should not be dropped or han-dled roughly.
• Ensure that no contamination enters the device.
• Some terminals in MAF and connector are gold-plated for corrosion resistance – DO
NOT probe.
Failure Modes
• Sensor open circuit
• Short circuit to battery voltage or ground
• Contaminated/damaged sensor element
• Air leak after MAF sensor
• Intake air restricted
• Resistance in the harness, causing signal offset
• Damaged sensor element
Failure Symptoms
• During driving the engine rpm might dip (before recovering)
• Difficulty in starting or start/stall
• Poor throttle response/engine performance
• Emissions incorrect
• Lambda control and idle speed control halted
• MAF signal offset
NP10V8102
SpecificationFunction
Supply Voltage 8 – 14V
(rated supply voltage: 14V)
Pin A Output (Vg)
Pin B Ground for Output (Vg)
Pin C Power Source
Pin D IAT Sensor Ground
Pin E IAT Sensor Output