The MAP (Manifold Absolute Pressure) sensor, absolute pressure of admission, detects the air pressure at the inlet of the vehicle and turns it into an electrical signal which is sent to the engine’s electronic control unit (ECU) in order to regulate the stoichiometric mixture.
The MAP sensors are classified in 2 groups according to their pressure range:
- Depression: 10 ÷ 130 kPa.
- Over-pressure: 10÷130 kpa ≤ P2 ≥ 400 kPa.
Some models do have a NTC type temperature sensor that allows the MAP to detect, not only the pressure, but also the air temperature at the inlet. This infor- mation is necessary for the ECU to calculate the mass of intake air in order to be able to adjust the air-fuel mixture.
The MAP sensor is located directly on the intake manifold or connected to it through a flexible tube.
The sensor element of the MAP is a piezoresistive type configured as a Wheatstone bridge, i.e., its electrical resistance varies according to the mechanical de- formation of a membrane.
The sensor element is integrated in a MEMS-type DIE which amplifies, performs a thermal compensation and conditions the signal. The incorporated digital electronics allow us to program the output signal between 0 ÷ 5 V, depending on the requirements we need in each reference. The DIE is mounted on a ceramic circuit and its electrical connections are made by bonding. All this is protected with a receptacle and a silicone gel. The electronic circuit is achieved through hybrid technology and is handled in a clean room due to its sensitive nature.
The output of the MAP is a linear relationship between the air pressure sucked in and the output voltage which corresponds to the following equation:
| Vout = S*P+Of |
where: Vout: output voltage (V).
S: sensitivity.
P: pressure of the air drawn in (kPa).
Of: offset. |
Technical Data
- Supply voltage..................................................5 V ± 0.5 V.
- Temperature range .........................................- 20ºC to +120°C *.
- Maximum and minimum temperatures.........- 40 to +140ºC.
- The sensor response time (t 10/90) .............1.5 ms.
- The maximum pressure ..................................700kPa **
*(within tolerances).
**(30ºC for 5s).
All these data are common to all MAP sensors, each specific reference has its own performance curve and specific tolerances.
The MAP sensor is composed of the following parts:
- Sensor element: consists in the electronic circuit mounted on a ceramic board.
- Housing: generally PBT +30 FV, contains the electronic circuit and the terminals. Usually the entrance of the air into the sensor is located here. (5).
- Terminals: to which is soldered the circuit by conventional tin soldering.
- Lid: can have on some occasion’s the entrance of the air into the sensor (5).
The sensor element contains:
A- Electronic circuit.
B- Ceramic board.
C- Protector of the DIE.
D- Silicone gel (wich protects the electronic circuit).
E- Electrical bonding.
Verify the body of the sensor, the wire and the connector ensuring their good condition. Furthermore check also if the body of the sensor shows any cracks, dents or impact that might have damaged it.
Keep in mind that, as a general rule, visual inspection is not sufficient to ensure the good or bad performance of the part, but it helps to make an initial diagnosis.
THE CAUSES OF FAILURE CAN BE:
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Damaged vacuum tubes.
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Damaged wires or connector.
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Damaged sensor element which results in pressure misreading.
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Leakage problem in the MAP sensor.
THE POSSIBLE EFFECTS OF A MALFUNCTIONING MAP SENSOR ARE:
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Switching on of the warning light “Check Engine”.
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Difficulties starting the engine.
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Low power or increased fuel consumption.
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Emission of black smoke due to spark delay or too long injection.
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Detonation due to an excessive progress.
The steps to follow when changing a MAP sensor are:
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Locate the MAP sensor on the vehicle (mounted on the intake manifold or fitted nearby).
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Disconnect the vacuum tube.
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Disconnect the connector of the MAP sensor.
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Remove the fitting screws or the anchoring system.
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Install the new sensor and fix it.
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Connect the vacuum tube.
Fitting Instructions
