How To Test The MAP Sensor (3.1L V6 Buick, Oldsmobile)

TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts

If you've reached this point, your TEST 1 result indicates that the MAP sensor's voltage signal does not decrease/increase as you apply/release vacuum to it.

There's a good chance that the MAP sensor is simply not receiving 5 Volts DC from the fuel injection computer.

To check this, we'll check that the wire labeled with the number 1 is delivering 5 Volts to the MAP sensor.

If 5 Volts are present in the wire labeled with the number 1, then we'll move on to the next test.

These are the test steps:

1. 1

   Place your multimeter still in Volts DC mode.

2. 2

   Disconnect the MAP sensor from its electrical connector.

3. 3

   Probe the wire labeled with the number 1, in the photo above, with the red multimeter test lead.

4. 4

   Now Ground the black multimeter test lead on the battery's negative (-) post.

5. 5

   Turn the key ON but with the engine OFF.

6. 6

   Your multimeter should show you either:
   
   1.) 4.5 to 5 Volts DC
   
   2.) 0 Volts.

OK, let's take a look at what your results mean:

CASE 1: The multimeter registered 5 Volts. This is the correct and expected test result and it confirms that the MAP sensor is getting power.

The next test is to make sure that it's getting Ground. Go to: TEST 3: Making Sure The MAP Sensor Is Getting Ground.

CASE 2: The multimeter DID NOT register 5 Volts. Without 5 Volts, the MAP sensor will not function.

Although it's beyond the scope of this tutorial to troubleshoot the cause of these missing 5 Volts, you have now eliminated the MAP sensor itself as bad.

Resolving the issue that is keeping these 5 Volts from being supplied will solve the MAP sensor issue on your GM 3.1L V6 car or mini-van.

TEST 3: Making Sure The MAP Sensor Is Getting Ground

So far, TEST 1 and TEST 2 have confirmed that:

• The MAP sensor voltage signal does not decrease/increase as vacuum is applied/released to it.
• The MAP sensor is receiving 5 Volts DC from the fuel injection computer.

For the last test, we're going to make sure that the wire labeled with the number 3 is delivering Ground to the MAP sensor.

To check for the presence of Ground in the wire labeled with the number 3, we're going to do a simple multimeter voltage test.

IMPORTANT: Ground is supplied to the MAP sensor by the fuel injection computer internally. So you have to be careful not to short this wire to battery 12 Volts or you'll fry the computer. The multimeter voltage test suggested in the following instructions is a safe way to test for the presence of Ground in the wire.

Alright, this is what you'll need to do:

1. 1

   Place your multimeter still in Volts DC mode.

2. 2

   Disconnect the MAP sensor from its electrical connector.

3. 3

   Probe the wire labeled with the number 3 in the image above, with the black multimeter test lead.

4. 4

   Connect the red multimeter test lead on the battery's positive (+) post.

5. 5

   Turn the key ON but with the engine OFF.

6. 6

   Your multimeter should show you either:
   
   1.) 10 to 12 Volts DC
   
   2.) 0 Volts.

OK, let's take a look at what your results mean:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct and expected test result and it confirms that the MAP sensor is getting Ground.

You can conclude the MAP sensor is fried and needs to be replaced if you have:

• Confirmed that the MAP sensor's voltage signal does not decrease/increase as you apply/release vacuum to the sensor (TEST 1).
• Confirmed that the MAP sensor is receiving 5 Volts DC (TEST 2).
• Confirmed in this test section that it's receiving Ground.

If you'd like to buy the original AC Delco MAP sensor and save, take a look at the section: Where To Buy The MAP Sensor And Save.

CASE 2: The multimeter DID NOT register 10 to 12 Volts. This test result tells you that the MAP sensor is not receiving Ground. Without Ground the MAP sensor will not function.

With this test result you can eliminate the MAP sensor itself as bad. Your next step is to find out why this Ground is missing and resolve the problem.

Usually, this missing Ground is due to an open-circuit problem in the wire between the MAP sensor's connector and the fuel injection computer's connector.

MAP Sensor Code Won't Go Away

Every now and then you'll run into a problem where the MAP sensor is good, either because you've tested it and your test results indicate that it's functioning correctly or you've replaced it with a new one, yet a MAP sensor trouble code keeps returning and illuminating the check engine light.

If this is happening in your case, then one or more of the following problems could be behind the issue:

1. The vacuum hose that connects the MAP sensor to the intake manifold is broken or cracked.
2. The engine has several cylinders with very low engine compression causing it to idle rough and thus producing low or erratic vacuum. For this I suggest a compression test.
   • How To Test Engine Compression (3.1L V6 Buick, Oldsmobile).
3. The MAP sensor is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
   • I have found that the best way to test these intermittent problems is to slightly tap the MAP sensor with the handle of a screw-driver and see if this tapping screws up the voltage readings as I apply vacuum.
4. The MAP sensor's connector is bad, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.
5. Your fuel pump is starting to go bad and is not sending enough fuel and/or fuel pressure up to the fuel injectors. I suggest a fuel pump test. See this tutorial:
   • How To Test The Fuel Pump (3.1L V6 Buick, Oldsmobile).

More 3.1L V6 Buick, Oldsmobile Tutorials

You can find a complete list of 3.1L V6 Buick (Oldsmobile) tutorials in this index:

• GM 3.1L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test Engine Compression Test (3.1L V6 Buick, Oldsmobile).
• How To Test A Blown Head Gasket (3.1L V6 Buick, Oldsmobile).
• How To Test The Fuel Pump (3.1L V6 Buick, Oldsmobile).
• How To Test The 24X Crankshaft Position Sensor (1995-1997 3.1L V6 Oldsmobile Cutlass Supreme).