In this tutorial, I'm going to show you how to test the manifold absolute pressure (MAP) sensor on the 2007, 2008, 2009 and 2010 3.9L Chevrolet Impala.
The absolute best way to accurately test the MAP sensor is with a vacuum pump and a multimeter and in this tutorial I'll show you how to do it.
This tutorial applies to the following vehicles since they use the exact same MAP sensor:
- 2008, 2009, 2010 3.9L V6 Chevrolet Impala.
- 2011 3.9L V6 Chevrolet Impala LS, LT and LTZ.
- 2008 3.9L V6 Chevrolet Uplander.
- 2008, 2009 3.9L V6 Pontiac G6 GT.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAP (2008-2010 3.9L Chevrolet Impala) (at: autotecnico-online.com).
Symptoms Of A Bad MAP Sensor
Your 3.9L Chevrolet Impala uses a mass air flow sensor to calculate the amount of air entering the engine.
It uses the manifold absolute pressure (MAP) sensor to calculate barometric pressure and engine load.
Since the MAP sensor is a key component of the fuel and engine management systems on your 3.9L Chevrolet Impala (Uplander or Pontiac G6), when it fails you're gonna' see the check engine light lit up by a MAP sensor trouble code. You'll see one of the following trouble codes:
- DTC P0107 MAP Sensor Circuit Low Voltage.
- DTC P0108 MAP Sensor Circuit High Voltage.
You're also going to see one or more of the following symptoms:
- Rough idle.
- ‘Rotten egg’ smell coming from the exhaust.
- Won't pass the state mandated emissions test.
- Bad gas mileage.
- Lack of power, rough idle, or hesitation.
- Engine cranks a long time before starting.
The MAP sensor is a 3 wire type sensor. This means that it has a power wire, a Ground wire and a signal wire. The table below has a brief description of each:
| Terminal | Wire | Description |
|---|---|---|
| 1 | LT GRN | MAP Signal |
| 2 | ORG/BLK | Ground |
| 3 | GRY | 5 Volts |
Where To Buy The MAP Sensor And Save
The MAP sensor can cost an arm and a leg at your local auto parts store (my local auto parts store sells the AC-Delco MAP sensor for $113!! You can buy it online for around $35! -see link below). Take a look at the following links and comparison shop because I think you'll save a few bucks by buying it online.
NOTE: The above MAP sensors fit the 2008-2010 3.9L V6 Chevrolet Impala, 2008 3.9L Uplander, and the 2008, 2009 3.9L Pontiac G6 GT.
TEST 1: Testing The MAP Sensor Voltage Signal
The key to successfully diagnosing the MAP sensor (as good or bad) is knowing that when it receives vacuum, its voltage signal decreases.
To be a bit more specific: when the MAP sensor receives vacuum it's voltage signal decreases and when it receives less vacuum, it's voltage signal increases.
When the engine is idling and there is low manifold vacuum pressure being applied to the MAP sensor it produces a higher voltage.
When you step on the accelerator pedal, the MAP sensor receives a higher amount of vacuum pressure and it produces a lower voltage signal.
So in our test, as we apply/release vacuum to the MAP sensor its voltage signal should decrease/increase.
If the MAP sensor is defective you'll see that its voltage signal stays stuck in one value as you apply/release vacuum to it.
IMPORTANT: To be able to read the MAP sensor voltage signal the MAP sensor must remain connected to its electrical connector. To access the voltage signal inside the wire you'll need to use a back probe or a wire piercing probe. You can see an example of this tool here: Wire Piercing Probe.
Let's get started:
- 1
Remove the MAP sensor from the intake manifold.
- 2
Connect your vacuum pump to the MAP sensor's vacuum inlet port. Reconnect the MAP sensor to its connector if you disconnected it.
- 3
Set your multimeter's selector to Volts DC mode.
- 4
Connect the red test lead to the LT GRN wire of the MAP sensor's connector. This wire is identified by the number 1 in the photo above.
Remember, the MAP sensor must remain connected to its 3 wire connector. - 5
Ground the black multimeter test lead directly on the battery negative (-) terminal.
- 6
Turn the Key on but don't start the engine. This will power up the MAP sensor and you should see a reading of 4.7 Volts DC on your multimeter.
- 7
Now, apply vacuum to the MAP sensor with the vacuum pump (or your mouth). The voltage signal value should decrease.
If you're using a vacuum pump: At 5 in.Hg → 3.9 Volts. At 10 in.Hg → 3 Volts. At 15 in.Hg → 2.1 Volts. At 20 in.Hg → 1.2 Volts. - 8
Release the vacuum. Once released, your multimeter should show the original voltage value.
Repeat this test step several times making sure that each time the voltage decreases/increases as you apply/release vacuum.
Let's take a look at what your test results mean:
CASE 1: The MAP voltage signal decreased/increased as you applied/released vacuum. This is the correct and expected test result.
This test results let you know that the MAP sensor on your 3.9L Chevrolet Impala (Uplander or Pontiac G6) is working correctly and it is not defective.
This test result also confirms that the manifold absolute pressure (MAP) sensor is getting 5 Volts and Ground from the fuel injection computer of your 3.9L V6 Impala (Uplander or Pontiac G6).
CASE 2: The MAP voltage signal DID NOT decrease/increase as you applied/released vacuum. This test result generally confirms that the MAP sensor is defective but not always.
The next step is to make sure that the MAP sensor is being fed with 5 Volts DC and Ground. For these two tests, go to: TEST 2: Verifying MAP Sensor Has 5 Volts And Ground.
CASE 3: The multimeter DID NOT register any voltage. This test result generally confirms that the MAP sensor is defective but not always.
The next step is to make sure that the MAP sensor is being fed with 5 Volts DC and Ground. For these two tests, go to: TEST 2: Verifying MAP Sensor Has 5 Volts And Ground.
