GM Service Manual Online
For 1990-2009 cars only

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.

The PCM calculates a predicted value for the MAP sensor based on throttle position and engine speed. The PCM then compares the predicted value to the actual MAP sensor signal. DTC P0106 will set if the MAP sensor signal is not within the predicted range.

Conditions for Running the DTC

    • DTC P0101, P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0401, P0404, P0405, P0410, P0440, P0442, P0443, and P0446 are not set.
    • The engine is running.
    • The engine speed is between 400-5,000 RPM.
    • The change in engine speed is less than 100 RPM.
    • The traction control is not active.
    • The throttle position is between 0-100 percent.
    • The change in idle air is less than 10 g/s.
    • The change in exhaust gas recirculation (EGR) position is less than 20 percent.
    • The A/C compressor clutch is steady.
    • The power steering is stable.
    • The power take off (PTO) is not active.
    • The clutch switch state does not change.
    • The brake switch state does not change.
    • All conditions are stable for 2 seconds.

Conditions for Setting the DTC

The actual MAP sensor signal is not within the predicted range for 1.5 seconds.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

    • Inspect for the following:
       - Restrictions in the manifold absolute pressure (MAP) sensor vacuum source
       - MAP sensor seal is missing or damaged
       - Vacuum hoses disconnected, damaged, or incorrectly routed
       - Intake manifold vacuum leaks
       - Vacuum leaks at the throttle body
    • If an intermittent condition exists, refer to Intermittent Conditions .

Test Description

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

  1. This step tests the MAP sensor's ability to correctly indicate barometric pressure. The value shown for the MAP sensor varies with altitude. 103 kPa is the approximate barometric pressure (BARO) displayed at or near sea level.

  2. This step tests the MAP sensor's ability to respond to an increase in engine vacuum.

  3. This step tests for a proper MAP sensor kPa with an applied vacuum.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the throttle angle parameter.
  4. Move the throttle slowly from closed to wide open position.

Does the throttle angle move steadily and completely from the first value to above the second value?

0 %

98 %

Go to Step 3

Go to DTC P0121

3

Important: In order to determine the correct MAP sensor value of barometric pressure for any elevation, perform either of the following:

    • Compare the MAP sensor value to the BARO value in a known good vehicle.
    • Obtain the local weather service barometer reading (in Hg). Multiply the reading by 3.4. The result indicates the correct BARO value in kPa for your area.

Is the MAP value normal for the altitude?

3 kPa

Go to Step 4

Go to Step 8

4

  1. Observe the MAP sensor kPa display on the scan tool.
  2. Start the engine.

Does the MAP sensor change value?

--

Go to Step 5

Go to Step 8

5

  1. Turn OFF the ignition.
  2. Remove the MAP sensor from the vacuum source. Refer to Manifold Absolute Pressure Sensor Replacement .
  3. Leave the electrical harness connected.
  4. Connect a hand vacuum pump to the MAP sensor.
  5. Turn ON the ignition, with the engine OFF.
  6. Observe the MAP sensor kPa as you SLOWLY apply vacuum 1 inch HG at a time. Each inch of vacuum should result in a 3-4 kPa drop in the MAP sensor display.
  7. Observe the MAP sensor kPa display for a skip or jump while increasing vacuum up to 20 inch HG.

Does the scan tool indicate a skip or a jump in the MAP sensor kPa?

--

Go to Step  16

Go to Step 6

6

Observe the MAP sensor kPa display with 20 inch HG of vacuum applied to the MAP sensor.

Does the scan tool indicate that the MAP sensor kPa is less than the specified value?

34 kPa

Go to Step 7

Go to Step 8

7

  1. Disconnect the MAP sensor from the hand vacuum pump.
  2. The MAP sensor kPa should return to the value observed in Step 3.

Does the MAP sensor kPa return to the original value that was observed in Step 3?

--

Go to Diagnostic Aids

Go to Step 16

8

  1. Turn OFF the ignition.
  2. Disconnect the MAP sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.

Does the scan tool indicate that the MAP sensor voltage is more than the specified value?

0.1 V

Go to Step 15

Go to Step 9

9

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.

Does the scan tool indicate that the MAP sensor voltage is near the specified value?

5 V

Go to Step 10

Go to Step 14

10

  1. Remove the jumper wire.
  2. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground.

Does the voltage measure more than the specified value?

5.2 V

Go to Step 12

Go to Step 11

11

Probe the low reference circuit with a test lamp connected to a battery positive voltage source.

Does the test lamp illuminate?

--

Go to Step 16

Go to Step 13

12

Test the 5-volt reference circuit of 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 20

Go to Step 17

13

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

Did you find and correct the condition?

--

Go to Step 20

Go to Step 17

14

Test the 5-volt reference and the signal circuit of the MAP sensor for high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 17

15

Test the signal circuit of 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 20

Go to Step 17

16

Inspect the MAP sensor for poor connections. 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 20

Go to Step 18

17

Inspect the PCM for poor connections. 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 20

Go to Step 19

18

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

Did you complete the replacement?

--

Go to Step 20

--

19

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 20

--

20

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 21

Go to Step 2

21

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK