Rick's Free Auto Repair Advice

P0107 Code for Manifold Absolute Pressure Sensor

Learn what a P0107 code means and how the most common causes

The Manifold Absolute Pressure sensor/Barometric Pressure Sensor (MAP/BARO)is a “speed density” method of determining the air-fuel ratio. The sensor measures intake manifold vacuum, which varies depending on how wide open the throttle is. MAP sensorHowever, while the pistons are pulling a vacuum on the down-stroke, outside barometric pressure is also pushing air into the cylinder. So the sensor actually takes two readings—one before the engine starts (barometer pressure) and one after the engine starts. Once the engine is running, the computer constantly monitors the changing voltage from the MAP to modify air-fuel mixtures to match the load.
wiring diagram for MAP sensorThe sensor receives a reference voltage from the computer and ground.

Depending on the type of MAP sensor, it can alter the returning voltage or generate a digital square wave back to the computer.

You can test a MAP sensor for correct barometric pressure readings with a digital multimeter. This is a typical chart of voltage values for a GM sensor, based on the altitude at your testing location.

chart of barometric pressure and voltages for MAP sensor

You can also test the MAP while it is running. Connect a vacuum gauge to the intake manifold and compare the reading on the gauge to the voltage reading you get from the MAP sensor.

The P0107 Code and what to do about it

chart of vacuum and voltages for MAP sensor

A P0107 code means the computer has detected a value that is outside acceptable limits during the barometric check portion of its operation.

Problems that can cause the MAP sensor signal to be outside the specified range:
– Leaking EGR valve
– Vacuum leaks
– Dirty fuel injectors
– Wrong fuel pressure
– Low engine compression
– Ignition miss
– Carbon deposits on the intake valves
– Valve problems

Don’t expect the MAP sensor signal to be normal if the engine has a problem that causes a low manifold vacuum.

Check the MAP sensor connector for corrosion. Remove the MAP sensor and check for signs of carbon buildup inside the sensor (it can’t be cleaned like a MAF sensor).

Before automatically replacing a MAP sensor for a P0107 code, make sure there are no vacuum leaks or disconnected vacuum lines.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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