The manifold absolute pressure sensor is a critical component of the engine management system, as such when it fails, engine performance will suffer.
In this tutorial, I'll show you how to test the MAP sensor on your 2.2L Chevrolet S10 and GMC Sonoma.
Your test results will help you to quickly and easily determine if the MAP sensor is good or bad.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAP (1994-1997 2.2L Chevrolet S10, GMC Sonoma) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 2.2L Chevrolet S10: 1994, 1995, 1996, 1997.
- 2.2L GMC Sonoma: 1994, 1995, 1996, 1997.
- 2.2L Isuzu Hombre: 1996, 1997.
Symptoms Of A Bad MAP Sensor
As you're probably already aware, the fuel system in your 2.2L Chevrolet S10 (GMC Sonoma) is a speed density type.
What this means in plain English, is that the engine relies heavily on the MAP sensor for engine load information to calculate the correct amount of fuel to inject into the cylinders.
This makes the manifold absolute pressure (MAP) sensor a critical component of the engine management system.
As such, when it fails, you'll see one of the following MAP sensor diagnostic codes illuminating the check engine light.
OBD I:
- 33: MAP Sensor Signal Voltage High.
- 34: MAP Sensor Signal Voltage Low.
OBD II:
- P0106: MAP Sensor System Performance.
- P0107: MAP Sensor Circuit Low Voltage.
- P0108: MAP Sensor Circuit High Voltage.
You'll also see one or more of the following symptoms:
- The engine won't start.
- The engine takes a long time to start (extended cranking time).
- Black smoke coming out of the tailpipe.
- Bad gas mileage.
- The engine idles rough when running.
- A lack of power when under load.
Where To Buy The MAP Sensor And Save
The manifold absolute pressure sensor on your 2.2L Chevrolet S10 (GMC Sonoma, Isuzu Hombre) isn't an expensive engine management system component.
You can buy it just about anywhere. If you'd like to save a few bucks on his purchase, take a look at the following links of known automotive brand MAP sensors (avoid knock-offs):
Not sure if the MAP sensor fits your vehicle? Don't worry. Once you get to the site, they'll make sure it fits by asking you the specifics of your vehicle. If it doesn't fit, they'll find you the right MAP sensor.
MAP Sensor Circuit Descriptions
You've probably already noticed that the MAP sensor's electrical connector has three wires coming out of it.
To successfully diagnose the MAP sensor, you'll need to know what each wire does.
The following table has a brief description of each wire:
| Wire | Color | Description |
|---|---|---|
| 1 | Grey (GRY) | 5 Volts |
| 2 | Light green (LT GRN) | MAP signal |
| 3 | Black (BLK) | Ground |
TEST 1: Testing The MAP Sensor Signal
When the MAP sensor receives vacuum, its voltage signal decreases. If the MAP sensor is bad, its voltage signal will stay stuck in one value no matter the amount of vacuum it receives.
So for your first test, I'm going to ask you to apply vacuum to the MAP sensor with a vacuum pump while checking it's output voltage signal (with a multimeter).
Don't worry, this is a pretty easy test to accomplish and will let you know right away if the MAP sensor is functioning correctly or not.
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, let's get started:
- 1
Remove the MAP sensor from its place on the intake manifold.
- 2
If you had to disconnect the MAP sensor from its electrical connector to remove it, reconnect it to the connector now.
- 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
Place your multimeter in Volts DC mode.
- 5
Connect the red multimeter probe to the wire that connects to the terminal labeled with the number 2 (in the image above).
This wire should be the light green (LT GRN) wire of the connector.
IMPORTANT: The MAP sensor must remain connected to its 3-wire connector. - 6
Connect the black multimeter test lead directly to the battery negative (-) terminal.
- 7
Turn the key ON but don't start the engine.
- 8
At this point your multimeter should register a value around 4.5 Volts DC.
- 9
Now, pump the vacuum pump to apply vacuum to the MAP sensor. The voltage should decrease.
- 10
Release the vacuum you applied to the MAP sensor. The voltage should increase.
OK, let's take a look at what your test results mean:
CASE 1: The MAP voltage signal decreased/increased as you applied/released vacuum to the sensor. This is the correct result and confirms that the MAP sensor is functioning correctly.
If a MAP sensor diagnostic trouble code keeps illuminating the check engine light, you can conclude the MAP sensor itself is not the cause. For more info, take a look at the section: MAP Sensor Code Won't Go Away.
CASE 2: The MAP voltage signal DID NOT increase/decrease as you applied/released vacuum. This test result usually indicates that the MAP sensor is bad.
Before replacing the MAP sensor, you need to make sure that it's getting 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 generally tells you that the MAP sensor is bad.
Before replacing the MAP sensor, you need to make sure that it's getting power and Ground. Go to the next test: MAP TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.
