Manifold Absolute Pressure Sensor Diagnosis. Chevrolet Impala 2003

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2003 🢒 Impala 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Manifold Absolute Pressure Sensor Diagnosis

Circuit Description

The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits:

•	5-volt reference circuit

•	Low reference circuit

•	MAP sensor signal circuit

The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The PCM should detect a high signal voltage at a high MAP, such as the ignition is ON, with the engine OFF, or at a wide open throttle (WOT). The MAP sensor is also used in order to determine the barometric pressure (BARO). This occurs when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range.

If the PCM detects a MAP sensor signal voltage that is excessively high DTC P0108 sets.

Test Description

The number below refers to the step number on the diagnostic table.

This step tests the MAP sensors ability to correctly indicate BARO.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Inspect for the following conditions:

•	Vacuum hoses disconnected, damaged, or incorrectly routed

•	MAP sensor seal missing or damaged

•	Restrictions in the MAP sensor vacuum source

•	Intake manifold vacuum leaks

Did you find and correct the condition?

Go to Step 24

Go to Step 3

Important: The vehicle used for the comparison is not limited to the same type of vehicle as is being serviced. A vehicle known to provide an accurate reading is acceptable.

Do you have access to another vehicle in which the MAP sensor pressure can be observed with a scan tool?

Go to Step 4

Go to Step 5

Turn ON the ignition, with the engine OFF.
Observe the MAP sensor pressure with a scan tool.
Observe the MAP sensor pressure in the known good vehicle with a scan tool.
Compare the values.

Is the difference between the values less than the specified value?

3 kPa

Go to Step 6

Go to Step 10

Important: The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high pressure and/or very low or very high temperature may cause a reading to be slightly out of range.

Turn ON the ignition, with the engine OFF.
Observe the MAP sensor pressure with a scan tool. Refer to Altitude Versus Barometric Pressure .
The MAP sensor pressure should be within the range specified for your altitude.

Does the MAP sensor indicate the correct barometric pressure?

Go to Step 6

Go to Step 10

Observe the MAP sensor pressure with a scan tool.
Start the engine.

Does the MAP sensor pressure change?

Go to Step 7

Go to Step 10

Turn OFF the ignition.
Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness.
Connect a hand vacuum pump to the MAP sensor.
Turn ON the ignition, with the engine OFF.
Observe the MAP sensor pressure with the scan tool.
Apply vacuum to the MAP sensor with the hand vacuum pump in 1 in Hg increments until 15 in Hg is reached. Each 1 in Hg should decrease MAP sensor pressure by 3-4 kPa.

Is the decrease in MAP sensor pressure consistent?

Go to Step 8

Go to Step 10

Apply vacuum with the hand vacuum pump until 20 in Hg is reached.

Is the MAP sensor pressure less than the specified value?

34 kPa

Go to Step 9

Go to Step 10

Disconnect the hand vacuum pump from the MAP sensor.

Does the MAP sensor pressure return to the value observed in step 4 or 5?

System OK

Go to Step 22

Disconnect the MAP sensor electrical connector.
Observe the MAP sensor parameter with the scan tool.

Is the voltage less than the specified value?

0.1 V

Go to Step 11

Go to Step 15

Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage more than the specified value?

5.2 V

Go to Step 16

Go to Step 12

Probe the 5-volt reference circuit of the MAP sensor with a test lamp that is connected to a good ground. Refer to Circuit Testing and Probing Electrical Connectors in Wiring Systems.

Is the test lamp OFF?

Go to Step 17

Go to Step 13

Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor.
Observe the MAP sensor parameter with the scan tool.

Is the voltage more than the specified value?

4.9 V

Go to Step 14

Go to Step 18

Turn OFF the ignition.
Remove the jumper wire.
Connect a jumper wire between each of the terminals in the MAP sensor harness connector and the corresponding terminal at the MAP sensor. Refer to Using Connector Test Adapters in Wiring Systems.
Turn ON the ignition, with the engine OFF.
Measure the voltage from the low reference circuit of the MAP sensor at the jumper wire terminal to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems.

Is the voltage more than the specified value?

0.2 V

Go to Step 19

Go to Step 20

Important: Disconnecting the PCM may eliminate the short during testing.

Important: The MAP sensor may have been damaged if the circuit was shorted to a voltage source.

Test the MAP sensor signal circuit between the PCM and the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 23

Important: Disconnecting the PCM may eliminate the short during testing.

Important: The MAP sensor may have been damaged if the circuit was shorted to a voltage source.

Test all of the branches of the 5-volt reference circuit that are shared with the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 23

Test the 5-volt reference circuit between the PCM and the MAP sensor for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 21

Test the MAP sensor signal circuit between the PCM and the MAP sensor for the following conditions:

•	A short to ground

•

An open

•	High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 21

Test the low reference circuit between the PCM and the MAP sensor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 21

Test for an intermittent and for a poor connection at the MAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 22

Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 23

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