How To Test The MAP Sensor (2003-2007 2.4L Honda Accord)

TEST 2: Applying/Releasing Vacuum To The MAP Sensor

In this test section, we're gonna dynamically check the MAP signal output. To be a bit more specific:

• As we apply vacuum to the MAP sensor, its voltage output should decrease.
• When we release the vacuum, the MAP sensor's output voltage should increase.

If the MAP sensor is bad, it'll generally produce a voltage value that'll stay stuck in one value regardless of the amount of vacuum you apply to it.

To accomplish this test, we'll connect our multimeter to the green with red stripe (GRN/RED) wire of the MAP sensor's 3-wire connector.

In the photo above, I've labeled the GRN/RED wire with the number 2 so that you can easily identify it on your Honda Accord.

NOTE: If you don't have a vacuum pump, don't worry. You can use your mouth to apply vacuum to the MAP sensor.

IMPORTANT: The MAP sensor must remain connected to its electrical connector to read the voltage within its signal wire. You'll need to use a back probe on the connector or a wire piercing probe on wire. You can see an example of this tool here: Wire Piercing Probe.

OK, these are the test steps:

1. 1

   Remove the MAP sensor from its place on the intake manifold.

2. 2

   If you had to disconnect the MAP sensor from its electrical connector to remove it, reconnect it to the connector now.

3. 3

   Connect your vacuum pump to the MAP sensor's vacuum inlet.
   
   You'll need to use a piece of vacuum hose to connect the vacuum pump to the MAP sensor.

4. 6

   Connect the black multimeter test lead directly to the battery negative (-) terminal.

5. 4

   Place your multimeter in Volts DC mode.

6. 5

   Connect the red multimeter probe to the GRN/RED wire of the MAP sensor's 3-wire connector.
   
   In the photo above, I've labeled the GRN/RED wire the number 2.
   
   IMPORTANT: The MAP sensor must remain connected to its 3-wire connector.

7. 7

   Turn the key ON (II) but don't crank or start the engine.

8. 8

   At this point your multimeter should register a value around 4.5 Volts DC.

9. 9

   Now, apply vacuum to the MAP sensor. The voltage should decrease.

10. 10

    Release the vacuum you applied to the MAP sensor. The voltage should increase.

Let's find out what your test results mean:

CASE 1: The MAP voltage signal decreased/increased as you applied/released vacuum. This is the correct test result.

The MAP sensor is working correctly (not defective) if you have:

• Confirmed the MAP signal voltage is at 4.5 Volts DC (TEST 1).
• Confirmed, in this test section, that the MAP signal voltage decreases/increases as you apply vacuum to the sensor.

CASE 2: The MAP voltage signal DID NOT decrease/increase as you applied/released vacuum. This test result usually indicates that the MAP sensor is bad.

To make sure the MAP sensor itself is defective, our test is to make sure the MAP sensor is getting 5 Volts. Go to: TEST 3: Making Sure The MAP Sensor Is Getting 5 Volts.

TEST 3: Making Sure The MAP Sensor Is Getting 5 Volts

Like any of the other engine management system components on your Honda Accord, the MAP sensor needs power to function.

This power is in the form of 5 Volts DC and are provided by your Honda Accord's fuel injection computer.

The wire that delivers these 5 Volts (from the computer to the MAP sensor) is the yellow with red stripe wire of the MAP sensor's 3-wire connector.

We'll perform a simple multimeter voltage test to confirm the presence of these 5 Volts in the YEL/RED wire.

NOTE: Be careful not to damage the front of the wire's female terminal with the multimeter test lead.

Let's get started:

1. 1

   Disconnect the MAP sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the black multimeter test lead to the battery's negative (-) post.

4. 4

   Turn the key ON (II) but don't crank or start the engine.

5. 5

   Gently probe the front of the female terminal that connects to the YEL/RED wire with the red multimeter test lead.

6. 6

   Your multimeter should register around 4.5 to 5 Volts DC.

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

CASE 1: The multimeter registered 4.5 to 5 Volts. This is the correct and expected test result.

Since the MAP sensor is receiving power, your next step is to make sure that it's getting Ground. Go to: TEST 4: Making Sure The MAP Sensor Is Getting Ground.

CASE 2: The multimeter DID NOT register 4.5 to 5 Volts. Without power, the MAP sensor will not function.

Although it's beyond the scope of this tutorial, your next step is to find out why these 5 Volts are missing and restore them.

The most likely cause of these missing 5 Volts is an open-circuit problem in the wire between the MAP sensor connector and the computer's connector.

Once you restore power to the MAP sensor, it'll start functioning again.

TEST 4: Making Sure The MAP Sensor Is Getting Ground

In this test section, we're going to make sure that the manifold absolute pressure sensor is getting Ground from the fuel injection computer.

The wire that delivers this Ground to the MAP sensor is the green with white stripe wire of the MAP sensor's 3-wire connector.

In the photo above, I've labeled the GRN/WHT wire with the number 3.

We're going to perform a simple multimeter voltage test to check for the presence of Ground in the green with white stripe wire.

CAUTION: The Ground the MAP sensor receives comes from the fuel injection computer. Be careful not to connect this wire to battery 12 Volts or you'll fry the computer. The multimeter voltage test I'm suggesting in the test instructions is a safe way to check for the presence of Ground in the wire.

Let's get going:

1. 1

   Disconnect the MAP sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

   Turn the key ON (II) but don't crank or start the engine.

5. 5

   Gently probe the front of the female terminal that connects to the GRN/WHT wire with the black multimeter test lead.

6. 6

   Your multimeter should register around 10 to 12 Volts DC.

OK, let's interpret your test result:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct test result and tells you that the MAP sensor is receiving Ground.

You can correctly conclude that the manifold absolute pressure sensor is bad and needs replacement if you have:

• Checked the MAP signal with the key on engine off (TEST 1).
• Confirmed the MAP sensor voltage signal does not decrease/increase as you apply/release vacuum to the sensor (TEST 2).
• Confirmed the MAP sensor is receiving 5 Volts (TEST 3).
• Confirmed the MAP sensor is receiving Ground (this test section).

CASE 2: The multimeter DID NOT register 10 to 12 Volts. Without Ground, the MAP sensor will not function.

Although it's beyond the scope of this tutorial, your next step is to find out why the MAP sensor is not receiving Ground and resolve the problem.

The most likely cause of this missing Ground is an open-circuit problem in the wire between the MAP sensor connector and the computer's connector.

Once you restore Ground to the MAP sensor, it'll start functioning again.

MAP Sensor Code Won't Go Away

It's not uncommon for the fuel injection computer to illuminate the check engine light with a MAP sensor diagnostic trouble code (DTC), even though the MAP sensor is OK.

What typically happens in these cases, is that the engine is suffering from an engine performance problem, which is causing the intake manifold vacuum to be erratic. The MAP sensor is simply picking up on the abnormal vacuum inside the intake manifold and reporting this to the fuel injection computer.

At this point, the fuel injection computer isn't able to differentiate between a bad MAP sensor and an engine performance issue causing the erratic vacuum values the MAP sensor is reporting.

If the MAP sensor DTC keeps coming back (after it testing OK or after replacing it), the following suggestions may help:

1. The o-ring (rubber gasket) on the vacuum inlet of the MAP sensor is missing 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 an engine compression test.
   • How To Test The Engine Compression (2003-2006 2.4L Honda Accord).
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. The fuel pump is failing. It'll send enough fuel to start the engine, but not enough to keep running under load. I suggest a fuel pump test to see if the fuel pressure is at specification.

More 2.4L Honda Accord Test Tutorials

If this tutorial was helpful, be sure and take a look at all of the 2.4L Honda Accord diagnostic tutorials in this index:

• 2.4L Honda Accord Index Of Articles.

Here's a sample of the tutorials you'll find there:

• How To Test Misfire Trouble Codes (2003-2006 2.4L Honda Accord).
• How To Test The Engine Compression (2003-2006 2.4L Honda Accord).
• How To Test The Fuel Injectors (2003-2006 2.4L Honda Accord).
• How To Test The MAP Sensor (1993-1996 2.2L Buick Century, Oldsmobile Cutlass Ciera).