The manifold absolute pressure (MAP) sensor is probably one of the easier engine management sensors to test.
The cool thing is you don't need a scan tool since you can quickly and accurately test the MAP sensor with a multimeter and a hand-held vacuum pump.
In this tutorial, I'll explain how to test it step by step. Your test results will help you determine if the MAP sensor is good or bad.
Contents of this tutorial:
- Symptoms Of A Bad MAP Sensor.
- Where To Buy The MAP Sensor And Save.
- MAP Sensor Circuit Descriptions.
- TEST 1: Testing The MAP Sensor Signal.
- TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.
- TEST 3: Making Sure The MAP Sensor Is Getting Ground.
- MAP Sensor Code Won't Go Away.
- More 2.2L Beretta, Cavalier, Corsica, And Sunfire Diagnostic Tutorials.
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAP (1992-1997 2.2L Beretta, Cavalier, Corsica, Sunfire) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 2.2L Chevrolet Beretta: 1992, 1993, 1994, 1995, 1996.
- 2.2L Chevrolet Cavalier: 1992, 1993, 1994, 1995, 1996, 1997.
- 2.2L Chevrolet Corsica: 1992, 1993, 1994, 1995, 1996.
- 2.2L Pontiac Sunfire: 1995, 1996, 1997.
Symptoms Of A Bad MAP Sensor
The fuel injection computer uses the manifold absolute pressure sensor to calculate the engine's load whenever the engine is running.
The fuel injection computer then uses this critical engine load information to inject the correct amount of fuel into the engine.
Since the fuel injection computer constantly monitors the MAP sensor's voltage output, the computer will set a MAP sensor diagnostic trouble code and illuminate the check engine light when it fails.
You'll see one of the following trouble codes:
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
Thankfully, the MAP sensor isn't an expensive engine management system component. The following links will help you comparison shop for known automotive brand MAP sensors. No knock-off MAP sensors!
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
| Wire | Color | Description |
|---|---|---|
| A | Black (BLK) | Ground |
| B | Light green (LT GRN) | MAP signal |
| C | Grey (GRY) | 5 Volts |
TEST 1: Testing The MAP Sensor Signal
To successfully diagnose the manifold absolute pressure sensor, you should know that:
- The MAP signal output voltage decreases as vacuum pressure is applied to the sensor.
- The MAP signal output voltage increases as vacuum is released to the sensor.
Generally, a bad MAP sensor's output voltage will stay stuck in one value as vacuum is applied/released to it.
To determine if the MAP sensor is good or bad, you'll apply vacuum to the MAP sensor while checking its output voltage signal with a multimeter.
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, these are the test steps:
- 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 labeled with the letter B (in the image above).
The wire labeled with the letter B is 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 examine your test results:
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.
