The manifold absolute pressure (MAP) sensor is a simple three-wire component easily tested with a multimeter.
In this tutorial, I'll explain how to do it in a step-by-step manner. With your test results, you'll easily be able to figure out if it's good or bad.
Contents of this tutorial:
This tutorial applies to the following vehicles:
- 3.1L V6 Chevrolet Beretta: 1994, 1995, 1996.
- 3.1L V6 Chevrolet Corsica: 1994, 1995, 1996.
- 3.1L V6 Chevrolet Lumina: 1995, 1996, 1997, 1998, 1999, 2000, 2001.
- 3.1L V6 Chevrolet Malibu: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- 3.1L V6 Chevrolet Monte Carlo: 1995, 1996, 1997, 1998, 1999.
- 3.1L V6 Pontiac Grand Am: 1994, 1995, 1996, 1997, 1998.
- 3.1L V6 Pontiac Grand Prix: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
Symptoms Of A Bad MAP Sensor
The manifold absolute pressure sensor is a key component of the engine management system.
Its job is to inform the fuel injection computer of the intake manifold's pressure. The computer then uses this information to calculate engine load.
When it fails, there will be a disturbance in the force. You'll see one or more of the following symptoms:
- The check engine light will be on with a MAP diagnostic trouble code (DTC) stored in the computer's memory.
- If your 3.1L V6 Chevrolet (Pontiac) is OBD II equipped, you'll see one of the following trouble codes:
- P0106: MAP Sensor System Performance.
- P0107: MAP Sensor Circuit Low Voltage.
- P0108: MAP Sensor Circuit High Voltage.
- If your 3.1L V6 Chevrolet (Pontiac) is 1994 or older, you'll see one of the following OBD I trouble codes:
- 33: Testing The MAP Sensor Signal Voltage High.
- 34: Testing The MAP Sensor Signal Voltage Low.
- Your vehicle won't start or will have a long cranking time before it starts.
- Black smoke coming out of the tailpipe along with really bad gas mileage.
- The engine idles rough when running and has a lack of power when accelerated.
You can learn more about the MAP sensor here: What Does The Map Sensor Do? (3.1L V6 Chevrolet, Pontiac).
Where To Buy The MAP Sensor And Save
The following links will help you to comparison shop for the MAP sensor of known automotive brand names (no knockoffs!)
Not sure if the MAP sensor fits your particular vehicle? Don't worry, once you get to the site they'll make sure it fits by asking you the specifics of your particular GM vehicle. If it doesn't fit, they'll find you the right MAP sensor.
TEST 1: Testing The MAP Sensor Signal
Alright, to get the MAP sensor diagnostic underway, we're going to make sure that the MAP sensor signal decreases/increases as you apply/release vacuum to the sensor.
If the MAP sensor is bad, the voltage signal will stay stuck at one value as you apply vacuum to it.
To check the MAP voltage signal, we're going to connect the multimeter to the wire labeled with the letter B in the photo above.
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 its voltage signal. You'll need to use a back probe or a wire-piercing probe on the MAP signal wire to access its signal. You can see an example of a wire piercing probe (and where to buy it) here: Wire Piercing Probe.
OK, these are the test steps:
Disconnect the MAP sensor from its vacuum hose.
On your specific vehicle, you may have to physically remove the MAP sensor from its mounting to disconnect it from its vacuum hose.
Connect your vacuum pump to the MAP sensor's vacuum inlet.
IMPORTANT: If you had to disconnect the MAP sensor from its electrical connector to remove it, reconnect it to it now.
Place your multimeter in Volts DC mode.
Connect the red multimeter probe to the wire labeled with the letter B (in the image above).
IMPORTANT: The MAP sensor must remain connected to its 3 wire connector.
Connect the black multimeter test lead directly to the battery negative (-) terminal.
Turn the key ON but don't start the engine.
At this point your multimeter should register 4.7 Volts DC.
Now, pump the vacuum pump to apply vacuum to the MAP sensor. The multimeter should register the following voltages at the following vacuum values (they may differ a little on your specific 2.8L, 3.1L, 3.4L GM car or mini-van):
1.) 0 in. Hg ...... 4.7 Volts.
2.) 5 in. Hg ...... 3.9 Volts.
3.) 10 in. Hg .... 3.0 Volts.
4.) 20 in. Hg .... 1.1 Volts.
Repeat this test step several times and each time, you should see the same values on your multimeter.
OK, let's take a look at what your vacuum pump test results mean:
CASE 1: Your multimeter registered the indicated voltages as you applied vacuum. This test result confirms that the MAP sensor is functioning correctly.
Now, if your vehicle still has a MAP sensor code lighting up the check engine on your instrument cluster, take a look at this section: MAP Sensor Code Won't Go Away.
CASE 2: Your multimeter registered voltage, but it did not increase/decrease as you applied/released vacuum. This test result usually tells you that the MAP sensor is defective.
To be absolutely sure the MAP sensor is bad, make sure that it's getting both power and Ground. Go to the next test: MAP TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.
CASE 3: Your multimeter registered 0 Volts. This test result usually means that the MAP sensor is bad but not always.
There's a good chance that the MAP sensor is not getting power or Ground. So the next step is to make sure that the MAP sensor is getting five votes from the fuel injection computer. Go to: MAP TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.