Last Updated on: 7th September 2023, 12:45 am
Also Known As:
- Manifold absolute pressure sensor
- engine load sensor
- pressure sensor
- boost sensor
The manifold absolute pressure (MAP) sensor is one of the sensors an engine control unit (ECU) employs to calculate fuel injection for the optimum air-fuel ratio by continually monitoring intake manifold pressure data.
It is typically used in fuel-injected engines.
A mass airflow (MAF) sensor is more frequently used than a MAP sensor, however turbocharged and forced induction engines often use both types of sensors.
Additionally, the MAP sensor plays a crucial part in assisting the ECU in determining when the ignition should start under various engine load conditions.
Whichever sensor your vehicle employs, without correct airflow data from a functional sensor, the ECU will not be able to optimise fuel injection.
A poor air-fuel ratio can impair performance and cause accelerated engine wear.
It can be challenging to identify a MAP sensor failure, but this article covers potential causes, warning signs, and how to replace one if it does.
How a Manifold Air Pressure Sensor Works
The MAP sensor is normally found on or near the throttle body on the intake manifold. The MAP sensor is located on the intake tract before the turbo on a turbocharged engine.
A sealed chamber with either a vacuum or a controlled pressure that is calibrated for the engine is located inside the MAP sensor.
A flexible silicon wafer, often known as a “chip”, with a current flowing through it separates the vacuum from the sensor and the vacuum from the intake manifold.
As soon as the key is turned on, the MAP sensor doubles as a barometric pressure sensor.
Since there is no suction applied to the MAP sensor when the key is turned (before the engine starts), the signal it sends to the ECU can be used to calculate air density as a barometric pressure reading.
The intake manifold pressure drops as the engine is running, causing a vacuum that is applied to the MAP sensor.
Less vacuum is created when the gas accelerator pedal is depressed because the pressure in the intake manifold rises.
The chip inside the MAP sensor will stretch upward into the sealed chamber as a result of the pressure variations, changing the voltage resistance, which instructs the ECU to inject additional fuel into the engine.
The clip flexes back to its idle position when the accelerator pedal is let off since the pressure in the intake manifold lowers as a result of this.
To calculate air density and precisely determine the engine’s air mass flow rate for the ideal air-fuel ratio, the ECU combines readings from the following senors.
- Manifold pressure readings from the MAP sensor
- Air intake temperature from the IAT (intake air temperature) sensor
- Coolant temperature ECT (engine coolant temperature) sensor
- Air pressure data from the barometric pressure sensor
- Engine speed (RPM) from the crankshaft position sensor
Various other sensors may be used to more accurately determine or alter the air-fuel ratio.
Why MAP Sensors Fail
MAP sensors, like the majority of electronic sensors, are susceptible to contamination. If the map sensor uses a hose, the hose may clog or leak, preventing it from monitoring pressure changes accurately.
Excessive vibrations from driving in some circumstances might loosen its connections.
In close proximity to the engine, electrical connectors can also overheat, melt or shatter. Corrosion or age-related deterioration might also result in sensor failure.
The MAP sensor should be changed if it fails.
Signs & Symptoms
The air-fuel ratio of an engine will be impacted by a malfunctioning MAP sensor. If the ratio is improper, combustion can occur at the wrong time, this is known as engine knock or detonation.
The internal engine components (such as pistons, rods, bearings, etc.) will suffer damage if pre-detonation happens and persists for a long period of time, resulting in engine failure.
Below are a few indicators of MAP sensor failure.
- Rich air-fuel ratio (rough idle, poor fuel economy, reduced performance, a strong smell of fuel)
- Lean air-fuel ratio (look for surging, stalling, lack of power, hesitation, backfiring through the intake, overheating)
- Failed emissions test
- Engine knocking and misfire
- MIL (check engine light) illumination / warning
If your engine is experiencing any of the symptoms above, consider troubleshooting your MAP sensor.
Common MAP sensor fault codes
Here is a list of codes that are associated with the MAP sensor to look for if your check engine light has turned on.
- 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
Note that these codes can occasionally be set by various sensors or other malfunctioning components.
Even if your engine is exhibiting the symptoms of a MAP sensor failure and is showing one or more of the above OBD fault codes, it is advised to test the sensor to make sure it is the issue.
Troubleshooting a MAP Sensor
Begin by following the step by step guide below to troubleshoot a faulty MAP sensor. Inspect the exterior for physical damage and if nothing arises use a multimeter to test the sensor.
To start, make sure there are no loose connections and inspect the connector and wiring for any damage, such as melted or cracked wires.
Check the pins after disconnecting the sensor; they should be clean, straight, and free of corrosion or bending.
Check for any signs of damage and make sure the hose has a tight connection to the sensor (if your vehicles sensor has a hose) before inspecting the line connecting the sensor to the intake manifold.
Check that the hose is clean inside and free of debris by looking inside it.
Proceed to the next step in the troubleshooting process if everything passes a physical inspection and there is no evidence of physical damage.
Test the Sensor Using a Multimeter
You can test the MAP sensor using a digital multimeter set to 20V and a vacuum pump.
- With the engine off, connect the multimeter ground to the negative terminal of the battery and check the voltage, it should be about 12.6 volts.
- Consult the manufacturer’s service manual to identify the signal, ground, and 5-volt reference and back-probe the wires.
- Turn the ignition switch on (without starting the engine). The multimeter should usually 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 and 2-3 volts for turbocharged vehicles. Your manufacturers manual should provide the exact specifications for your vehicle.
- Start the engine with the signal wire back-probed. The multimeter should display a voltage of 0.5-1.5 volts at sea level on non-turbocharged vehicles and 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 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.
Replace a Faulty MAP Sensor
MAP sensor replacement instructions vary from vehicle to vehicle; for specifics, consult the manufacturer’s service manual.
After the defective sensor has been taken out, installing the replacement component is simple.
- The MAP sensor should be located on the intake manifold, either on or close to the throttle body.
- Any bolts or screws keeping the sensor in place should be removed.
- The electrical connector should be disconnected. Avoid removing the connector by force since it may have a locking tab that needs to be pulled out in order to free the connector from the sensor.
- Remove the vacuum hose from the sensor, if necessary. When changing the sensor, it is advised to also change the vacuum hose.
- The new and old sensors should be compared to verify the correct part is being installed.
- Reconnect the vacuum hose if necessary.
- Reconnect the electrical connector for the sensor.
- Any bolts or screws holding the sensor in place should be replaced.
- Verify that all connections are secure by checking them again.
- The check engine light may need to be reset with a diagnostic tool, depending on the car and whether a fault code was set.