Manifold Absolute Barometric Pressure Sensor testing

 

 

 

 

 

 

 

 

Hi!

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:

1. Checking if the unit get a good GND.
2. Checking if the unit get a good 5V reference voltage from the ECU.
3. Checking the output signal.

I must to test the sensor on my service bench, without the access to the car.

So I did this:

1. Checked if the unit is shorted out with my DMM between GND and 5V pin.
2. Applied 5V through my lab power source.
3. Applied a rubber tube to the middle hole where the sensor senses the pressure/vacuum.
4. 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.

NOTE!

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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Note: You can check his previous post in the below link:

https://jestineyong.com/how-to-build-your-own-rs232-to-ttl-converter/

 

13 Comments

1. 

   doraiswamy SR

   December 12, 2017 at 12:00 pm

   but what was the initial nature of fault / issue of the car for which you suspected the sensor?

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   • 

     Chris

     January 1, 2018 at 3:42 am

     Hi!
     Thanks for supporting my article.
     The first problem with the car was does it cant rev up over 3000rpm, what was actually LIMP mode. That is something like safe mode on a windows system.
     Than the MIL Male function Indication Lamp was on.
     After scanning the vehicle with scan tool I recognized a problem with one and more barometric sensors.

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2. 

   Robert Calk

   December 12, 2017 at 1:27 pm

   Good job, Christian. You mentioned the MAP sensor and then the BPS(Barometric Pressure Sensor), and use a chart for the BPS. Are they the same now? When I was a mechanic, the MAP and BPS sensors were separate sensors.

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   • 

     Chris

     January 1, 2018 at 3:48 am

     Hi!
     Thanks for supporting my article.
     A good question, I put a thump up for this question made by you.
     Actually they are two separated parts but they act same.
     If I would wrote two articles in 99% the writing would be the same.
     On some vehicles only the housing is different, but on some there are deference in the voltage level at the output.
     Actually the testing method would be the same.
     The MAP (Manifold Absolute Pressure sensor ) and the BARO (Barometric Pressure Sensor) are barometric pressure sensors.
     They both measure the pressure in a specific environment.
     The concepts are same just the name are different.

     My best regards.

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     • 

       Ray S.

       July 15, 2018 at 7:35 am

       Thanks for your article.

       Ray from Canada

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3. 

   Yogesh Panchal

   December 12, 2017 at 5:37 pm

   Thanks for sharing your experience!Christian Robert

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4. 

   Albert van Bemmelen

   December 13, 2017 at 4:06 am

   Another very specialized repairing and testing article on car electronics Christian. Even those of us not familiar with car engineering learn new things this way which may come in handy in time.

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5. 

   Humberto

   December 13, 2017 at 10:27 pm

   Hi Chris, I've really enjoyed reading your article. Congrats.

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6. 

   Henrique Jorge Guimarães Ulbeich

   December 16, 2017 at 10:23 pm

   Dear Chris, are there differences between MAP and BPS?

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   • 

     Chris

     January 1, 2018 at 3:50 am

     Hi!
     Thanks for supporting my article.
     Actually no but from technical viewing and design yes.
     Please read my post what I wrote as an answer to Mr. Robert Calk upper there.

     My best regards.

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     Reply
7. 

   Parasuraman S

   December 24, 2017 at 12:00 am

   Hitherto untouched area! Good to learn!

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8. 

   Ulises Aguilar Pazzani

   December 29, 2017 at 12:09 pm

   Mr Robert Adzic grate article ,keep it up and merry Christmas and Happy New Year

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9. 

   Chris

   January 1, 2018 at 3:52 am

   Hi to all!
   Sorry because I'm late with my answers, but private problems...

   Ok.
   If any other questions are there please post it, I will answer if I know.

   I wish Happy New Year to all the peoples who are here and out of here.
   I hope to enjoy together our writings and be together in the upcoming new year.

   My best regards.

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   Reply

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