Manifold Absolute Pressure Sensor Output Diagnosis. Oldsmobile Alero 2000

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 2000 🢒 Alero 🢒 Engine 🢒 Engine Controls - 2.4L 🢒 Manifold Absolute Pressure Sensor Output Diagnosis

Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The manifold absolute pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load (intake manifold vacuum) and RPM changes and converts the changes into a voltage output. The powertrain control module (PCM) sends a 5 volt reference voltage to the MAP sensor. As the manifold pressure changes, the output voltage of the sensor also changes. By monitoring the sensor output voltage, the PCM determines the manifold pressure. A lower pressure (low voltage) output voltage will be about 1.0 to 1.5 volts at idle. A higher pressure (high voltage) output voltage will be about 4.5 to 4.8 V at wide open throttle (WOT). The MAP sensor is also used to measure the barometric pressure under certain conditions , allowing the PCM to make adjustments for different altitudes. The PCM uses the MAP sensor to control fuel delivery and ignition timing.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

Important: Be sure to use the same diagnostic test equipment for all measurements.

Applying 34 kPa (10 in Hg) vacuum to the MAP sensor should cause the voltage to be 1.5 to 2.1 volts less than the voltage at Step 3. Upon applying vacuum to the sensor, the change in the voltage should be instantaneous. A slow voltage change indicates a malfunctioning sensor.

Important: Make sure that the connector remains securely fastened.

Move the sensor connector by hand (only) while observing a scan tool in order to test for an intermittent connection. An output that changes more than 0.10 volt indicates a bad connection. If the output is OK, replace the sensor.

Manifold Absolute Pressure (MAP) Sensor Output Check

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Use a scan tool in order to compare the BARO reading with a known good vehicle.

Are the BARO readings within the specified value of each other ?

3 kPa

Go to Step 3

Go to Step 5

Disconnect and plug the vacuum source to the MAP sensor.
Connect a hand vacuum pump to the MAP sensor.
Use a scan tool in order to observe the MAP sensor voltage.
Apply 34 kPa (10 in Hg) of vacuum to the MAP sensor and observe the MAP sensor voltage again.
Subtract the second voltage from the first voltage.

Is the difference more than specified value?

1.5 V

Go to Step 4

Go to Step 5

Inspect the MAP sensor vacuum source for the following conditions:

•

Any leaks

•	Any restrictions

Verify that the vacuum supply is to the MAP sensor only
If a problem is found, repair as necessary.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

Turn off the ignition.
Inspect the MAP sensor connector for a faulty connection. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

Turn off the ignition.
Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .

Did you complete the repair?

Go to Step 7

Start and operate the vehicle within the conditions under which the original symptom was observed.

Does the system operate properly?

System OK

Go to Step 2