Manifold Absolute Barometric Pressure Sensor testing
A couple of days ago I got a mission how to test a MAP ( Baro ) sensor from a car. The MAP sensor is converting the engine vacuum – Manifold Absolute Pressure into an electric signal and that signal is delivered to the car ECU for future processing. Here is the picture about the MAP I had to test:
So, everything is written on the label of the sensor. It will be simple to test. Hmmm… yes and no.
Here is a small testing process step s list:
- Checking if the unit get a good GND.
- Checking if the unit get a good 5V reference voltage from the ECU.
- Checking the output signal.
I must to test the sensor on my service bench, without the access to the car.
So I did this:
- Checked if the unit is shorted out with my DMM between GND and 5V pin.
- Applied 5V through my lab power source.
- Applied a rubber tube to the middle hole where the sensor senses the pressure/vacuum.
- Applied vacuum with my vacuum solder gun (of course I disconnected the heating element before.)
When I measured the voltage between GND and the OUT (middle) pin I got a voltage around 2.3V.
That was almost enough for me to make the decision does this sensor is bad according the datasheet of measurement which is the next picture:
According on the table, between the B pin which is the middle pin on the sensor and GND should be a voltage around 4.9V when the sensor is powered on but the engine is not running. That means my simulation, actually is the sensor powered on my bench, through my lab power source.
This is the condition of ignition on. I should have a reading around 4.9V but I have only around 2V. That means the sensor is faulty.
This voltage can be far out of specification if it would be tested on different altitude what is not mentioned in the data sheet, but I think the sea level should be taken in calculation too. If this test would be done 2-3km higher than sea level the reading would be much different. So be warned about this phenomenon. The next test what I done was the applying vacuum to the middle hole and check the voltage on DMM.
As the vacuum rise the voltage dropped and vice versa. That means the sensor is actually reacting to the pressure change but for some reason it stuck on half the way, looks like it is somehow blocked.
Maybe oil is entered inside and makes some trouble or some dust or mix of that two, who knows.
One thing is certain, this sensor is faulty and the DTC ( Diagnostic Trouble Code ) P1105 was triggered actually because of the non accurate sensor, what was later reported to me also.
I hope you enjoy this tutorial and will save lot of repair time.
This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.
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