Manifold Air Pressure Sensor (MAP)
Updated: Jan 9
The manifold absolute pressure (MAP) sensor is a device used by the engine control unit (ECU) to calculate the fuel injection needed for the optimal air-fuel ratio in an internal combustion engine.
MAP sensors are also commonly referred to as:
Manifold absolute pressure sensor
Engine load sensor
Pressure sensor
Boost sensor
The MAP sensor continually monitors intake manifold pressure data and is typically used in fuel-injected engines. It is also commonly used in turbocharged and forced induction engines, along with a mass airflow (MAF) sensor.
In addition to its role in fuel injection, the MAP sensor helps the ECU determine when ignition should occur under various engine load conditions.
If the MAP sensor is not functioning properly, the ECU will not be able to optimise fuel injection, which can affect engine performance and cause accelerated wear.
Table of Contents:
Location & Appearance of the MAP Sensor
A manifold absolute pressure (MAP) sensor is a small electronic device that is typically located on or near the throttle body on the intake manifold of an internal combustion engine, or on the intake tract before the turbo in a turbocharged engine.
It typically has a cylindrical shape sensor with a rectangular shaped body, it's usually is made of plastic.
The MAP sensor may have a hose or tube connected to it, which carries the vacuum or pressure from the intake manifold. It may also have electrical connectors and wiring, which allow it to send data to the engine control unit (ECU).
The image below shows what MAP sensors usually look like.
The MAP sensor may be mounted to the engine using bolts or clips. It is usually small enough to fit in the palm of your hand and may have a label or markings indicating its manufacturer and model.
How Manifold Air Pressure Sensors Work
It consists of a sealed chamber with a calibrated vacuum or controlled pressure and a flexible silicon wafer known as a "chip" that separates the vacuum from the sensor and the vacuum from the intake manifold.
When the key is turned on, the MAP sensor acts as a barometric pressure sensor, sending a signal to the ECU that can be used to calculate air density.
As the engine runs, the intake manifold pressure drops, creating a vacuum that is applied to the MAP sensor.
When the throttle / accelerator pedal is pressed, the pressure in the intake manifold rises, reducing the vacuum.
This causes the chip inside the MAP sensor to stretch into the sealed chamber, changing the voltage resistance and signaling the ECU to inject more fuel into the engine.
When the accelerator pedal is released, the chip returns to its idle position as the pressure in the intake manifold decreases.
To determine the engine's air mass flow rate for the ideal air-fuel ratio, the ECU combines readings from the following sensors.
Manifold air pressure (MAP) sensor
Intake air temperature (IAT) sensor
Engine coolant temperature (ECT) sensor
Barometric pressure sensor
Other sensors may also be used to more accurately determine or adjust the air-fuel ratio, such as the mass air flow (MAF) sensor.
Causes of MAP Sensor Failure
The Manifold Air Pressure (MAP) sensor is an electronic device that is used to measure changes in air pressure within the engine. However, like other electronic sensors, it can be susceptible to contamination, which can cause it to malfunction.
Hose failure: If the MAP sensor is connected to the engine via a hose, this hose may become clogged or leak, preventing the sensor from accurately measuring pressure changes.
Vibrations: Excessive vibrations from driving in certain conditions may loosen the connections of the MAP sensor, causing it to fail.
Heat: Electrical connectors that are located close to the engine may become overheated and melt or shatter, which can also lead to sensor failure.
Corrosion and age: Over time, corrosion and age-related deterioration may also cause the MAP sensor to fail. If the MAP sensor fails, it should be replaced to avoid further engine damage.
Signs of a Failing MAP Sensor
To diagnose a MAP sensor issue, a mechanic will typically use a diagnostic tool to check for fault codes and perform a visual inspection of the sensor and related components.
The manifold air pressure sensor helps to regulate the air-fuel ratio and prevent engine knock, which can cause damage to the internal engine components such as pistons, rods, and bearings.
There are several signs that may indicate a failure of the MAP sensor. These include a rich air-fuel ratio, which can cause a rough idle, poor fuel economy, reduced performance, and a strong smell of fuel.
A lean air-fuel ratio may manifest as surging, stalling, lack of power, hesitation, backfiring through the intake, and overheating.
Other indicators of a MAP sensor failure may include a failed emissions test, engine knocking and misfire, and the illumination of the MIL (malfunction indicator lamp) or warning. If your engine is exhibiting any of these symptoms, it may be worth considering troubleshooting the MAP sensor.
Common MAP Sensor DTCs
If your check engine light has turned on, there are certain codes that may be associated with the manifold air pressure (MAP) sensor. Below is a list of codes that may be relevant.
P0068: MAP / MAF - Throttle Position Correlation
P0069: Manifold Absolute Pressure / Barometric Pressure Correlation
P0105: MAP Circuit Malfunction
P0106: MAP / Barometric Pressure Circuit Range / Performance Problem
P0107: Manifold Absolute Pressure / Barometric Pressure Circuit Low Input
P0108: MAP Pressure Circuit High Input
P0109: MAP / Baro Pressure Circuit Intermittent
P1106: MAP / Baro Pressure Circuit Range / Performance Problem
P1107: Barometric Pressure Sensor Circuit Low Voltage
It's important to keep in mind that certain codes related to the MAP sensor may also be set by other malfunctioning components or sensors.
Therefore, even if your engine is exhibiting the symptoms of a MAP sensor failure and displaying one or more of the codes listed above, it is recommended to perform testing to confirm that the sensor is the cause of the problem.
It is advised to consult a mechanic or repair manual for guidance on how to properly test the MAP sensor to ensure accuracy.
MAP Sensor Troubleshooting
To troubleshoot a faulty manifold air pressure (MAP) sensor, follow the steps below.
Physical Inspection
Physically inspect the MAP sensor using the steps below.
Inspect the sensor for any physical damage, such as cracks or melted wires.
Check the connections to the sensor, including the pins and hose (if applicable). Make sure they are clean and secure.
Inspect the hose connecting the sensor to the intake manifold for any debris or damage.
If there is no evidence of physical damage, proceed to the next step in the troubleshooting process, which is testing the sensor with a multimeter.
Test the Sensor
To test a manifold air pressure (MAP) sensor, you will need a digital multimeter set to measure voltage and a vacuum pump. Below is the process to test the sensor.
Connect the multimeter to the battery and check the voltage. It should be about 12.6 volts.
Identify the signal, ground, and 5-volt reference wires for your vehicle using the manufacturer's service manual.
Turn the ignition switch on (without starting the engine). The multimeter should display 4.5-5 volts for the 5-volt reference, 0 volts for the ground wire, and 0.5-1.5 volts for the signal wire on non-turbocharged vehicles or 2-3 volts on turbocharged models. These are the expected values at this stage of the test.
Start the engine and back-probe the signal wire. The multimeter should display a voltage of 0.5-1.5 volts at sea level on non-turbocharged vehicles or 2-2.5 volts on turbocharged models.
Turn the engine off, but keep the ignition on. Disconnect the MAP sensor from the intake.
Connect a hand vacuum pump to the sensor and take note of the current voltage from the signal wire.
Increase the vacuum on the sensor using the vacuum pump. The voltage should steadily drop as the vacuum increases.
If the voltage is significantly different from the expected values at any point during the test or if the voltage change is irregular, the MAP sensor should be replaced.
Replacing the Sensor
To replace a faulty manifold air pressure (MAP) sensor, follow the steps below.
Refer to the manufacturer's service manual for specific instructions for your vehicle.
Disconnect the negative (ground) terminal from the battery.
Locate the MAP sensor on the intake manifold, either on or close to the throttle body.
Remove any bolts or screws holding the sensor in place.
Disconnect the electrical connector for the sensor, being careful not to damage it or the locking tab (if applicable).
If necessary, remove the vacuum hose from the sensor. It is recommended to replace the hose when changing the sensor.
Compare the new and old sensors to verify that the correct part is being installed.
Reconnect the vacuum hose, if applicable.
Reconnect the electrical connector for the sensor.
Replace any bolts or screws holding the sensor in place.
Check all connections to make sure they are secure.
Reconnect the negative (ground) battery terminal.
Depending on the car and whether a fault code was set, you may need to reset the check engine light using a diagnostic tool.