In this tutorial, I'm going to explain how to test the MAP sensor with a simple multimeter. You'll be able to easily find out if the MAP sensor is bad or not.
All of the test steps are explained in a step-by-step manner and in plain English!
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 3.1L V6 Buick Century: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004.
- 3.1L V6 Buick Regal: 1994, 1995, 1996.
- 3.1L V6 Buick Skylark: 1994, 1995, 1996.
- 3.1L V6 Oldsmobile Achieva: 1994, 1995, 1996, 1997, 1998.
- 3.1L V6 Oldsmobile Cutlass: 1997, 1998, 1999.
- 3.1L V6 Oldsmobile Cutlass Ciera: 1994, 1995, 1996.
- 3.1L V6 Oldsmobile Cutlass Supreme: 1993, 1994, 1995, 1996, 1997.
Symptoms Of A Bad MAP Sensor
The MAP sensor is a critical component of the engine management system since the fuel injection computer uses the information it provides to calculate engine load.
So when it fails, engine performance will suffer. 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 GM 3.1L V6 car or mini-van is OBD II equipped, you'll see one trouble codes:
- P0106: MAP Sensor System Performance.
- P0107: MAP Sensor Circuit Low Voltage.
- P0108: MAP Sensor Circuit High Voltage.
- If your GM 3.1L V6 car or mini-van is 1994 or older, you'll see DTCs:
- 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 Buick, Oldsmobile) .
Where To Buy The MAP Sensor And Save
The following links will help you comparison shop for the manifold absolute pressure (MAP) sensor. All of the recommended MAP sensors are of known automotive brands -no knockoff MAP sensors!
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
The first thing that we're going to do, to get our MAP sensor diagnostic underway, is to check that the MAP sensor is producing a voltage signal that decreases/increases as we apply/release vacuum to it.
To accomplish this task, we need to remove the MAP sensor from its place on the intake manifold. But once removed, it has to be reconnected to its electrical connector.
Since the MAP sensor has to remain connected to its electrical connector to test it, you'll need to use a back probe or a wire piercing probe the MAP signal wire and access the voltage signal within it. You can see an example (and where to buy this tool) here: Wire Piercing Probe.
NOTE: if you don't have a vacuum pump, don't worry. You can use your mouth to apply vacuum to the MAP sensor.
OK, to get this show on the road, this is what you need to do:
Remove the MAP sensor from its place on the intake manifold.
You'll also need to disconnect it from the vacuum hose that it connects to.
If you had to disconnect the MAP sensor from its electrical connector to remove it, reconnect it to it now.
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.
Place your multimeter in Volts DC mode.
Connect the red multimeter probe to the wire labeled with the number 2 (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 examine your test results:
CASE 1: The MAP voltage signal decreased/increased as you applied/released vacuum to the sensor. This test result confirms that the MAP sensor is functioning correctly.
Now, if your vehicle still has the MAP sensor code lighting up the check engine on your instrument cluster, take a look at the section: MAP Sensor Code Won't Go Away for more info.
CASE 2: The MAP voltage signal 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.