TEST 2: Verifying MAP Sensor Has 5 Volts And Ground
In some cases the MAP sensor doesn't get either 5 Volts or Ground from the fuel injection computer due to an electrical wiring problem.
So if in TEST 1 the MAP sensor did not react to you applying vacuum to it it's a good idea to make sure that it's getting power and Ground.
5 Volts are supplied to the MAP sensor through the gray (GRY) wire of the MAP sensor's connector. This wire is labeled with the number 3 in the photo above.
Ground is supplied to the MAP sensor through the pink with black stripe (PNK/BLK) wire of the MAP sensor's electrical connector. This wire is labeled with the number 2 in the photo above.
IMPORTANT: Be careful not to pass 12 Volts DC (battery power) to the Ground wire or you will fry the fuel injection computer on your 3.9L V6 Chevy Impala (Uplander or Pontiac G6). The multimeter voltage test indicated in the test steps below is one of the safest way to test this Ground.
These are the test steps:
- 1
Place your multimeter in Volts DC mode.
- 2
Turn the key on but don't start the engine.
- 3
Verify that the GRY wire has voltage (4.5 to 5 Volts DC) with the key on but engine off.
Connect the red multimeter test lead (using the appropriate tool) to the GRY wire.
Connect the black multimeter test lead to the negative battery terminal.
Your multimeter should read 4.5 to 5 Volts DC. - 4
Verify that the ORG/BLK wire has Ground with the key on but engine off.
Connect the black multimeter test lead (using the appropriate tool) to the ORG/BLK wire.
Connect the red multimeter test lead to the positive battery terminal.
Your multimeter should read 12 Volts DC.
These are what the test results mean:
CASE 1: The MAP sensor is getting 5 Volts and Ground. This is the correct and expected test result.
You can conclude that the MAP sensor defective only if you have:
- Tested the MAP sensor signal and it is not decreasing/increasing as you apply/release vacuum to the MAP sensor.
- Confirmed that the MAP sensor is getting both 5 Volts and Ground.
CASE 2: The MAP sensor IS NOT getting 5 Volts. The MAP sensor will not function if it isn't getting these 5 Volts.
Although it's beyond the scope of this tutorial to find out why these 5 Volts are missing, the most likely cause is an open-circuit problem in the MAP sensor connector's wiring.
CASE 3: The MAP sensor IS NOT getting Ground. The MAP sensor will not function if it isn't getting Ground from your 3.9L Chevy Malibu's fuel injection computer.
Although it's beyond the scope of this tutorial to find out why this Ground is missing, the most likely cause is an open-circuit problem in the MAP sensor connector's wiring.
More GM 3.9L Test Tutorials
If this tutorial was helpful, be sure and take a look at all of the 3.9L Chevrolet Malibu and Impala test tutorials in this index: GM 3.9L Index Of Articles.
Here's a sample of the tutorials you'll find there:
- How To Test The Engine Compression (2006-2010 3.9L V6 Engine).
- How Often Should I Replace The Spark Plugs (2006-2010 3.9L V6 Engine).
- How To Test A Blown Head Gasket (2006-2010 3.9L V6 Engine).
- Ignition System Wiring Diagram (2006-2007 3.9L Chevrolet Malibu).
If this info saved the day, buy me a beer!
