GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC 033

Circuit Description

The manifold absolute pressure (MAP) sensor responds to changes in the manifold vacuum. The electronic control module (ECM) receives this information as a signal voltage that will vary from about 1-1.5 volts at closed throttle, idle, to 4.5-5 volts at wide open throttle.

Conditions for Setting the DTC
    • DTCs 021 and 022 are not set.
    • The throttle angle is below 5 percent.
    • The MAP sensor signal indicates greater than 95 kPa (13.7 psi).
    • These conditions are present for 5 seconds.

Diagnostic Aids
    • If the connections are OK, monitor the MAP sensor signal voltage while moving related connectors and the wiring harness. If the failure is induced, the display on the scan tool will change. This may help to isolate the location of an intermittent malfunction.
    • With the ignition ON and the engine OFF, the MAP sensor pressure is equal to the atmospheric pressure. This information is used by the ECM as an indication of altitude. Comparison of these readings with a known good vehicle with the same MAP sensor is a good way to measure the accuracy of a questionable MAP sensor. The readings should be the same within 0.4 volt.

Step

Action

Values

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Inspect the vacuum line from the manifold absolute pressure (MAP) sensor for cracks, leaks, or restrictions.

Is the problem found?

--

Go to Step 3

Go to Step 4

3
  1. Repair or replace the vacuum line as needed.
  2. Road test the vehicle.
  3. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

--

4
  1. Connect the scan tool to the data link connector (DLC).
  2. Turn the ignition ON.

Does the scan tool show the MAP sensor voltage above the value specified?

4 V

Go to Step 5

Go to Step 6

5
  1. Disconnect the vacuum line from the MAP sensor.
  2. Apply 68 kPa (9.28 psi) of vacuum to the MAP sensor.

Does the scan tool show the MAP sensor voltage within the value specified?

1-1.5 V

Go to Diagnostic Aids

Go to Step 6

6
  1. Turn the ignition to LOCK.
  2. Disconnect the MAP sensor connector.
  3. Turn the ignition ON.
  4. Measure the voltage between MAP sensor connector terminals 1 and 3.

Does the voltage measure within the value specified?

4.5-5.5 V

Go to Step 7

Go to Step 8

7

Connect a fused jumper between the MAP sensor connector terminals 2 and 1.

Does the scan tool show the MAP sensor voltage above the value specified?

4 V

Go to Step 13

Go to Step 11

8

Measure the voltage between the MAP sensor connector terminal 1 and ground.

Does the voltage measure within the value specified?

4.5-5.5 V

Go to Step 9

Go to Step 10

9

Inspect for a short to battery voltage in the wire between the MAP sensor connector terminal 3 and the engine control module (ECM) connector terminal D15.

Is the problem found?

--

Go to Step 12

Go to Step 11

10

Inspect for a short to battery voltage in the wire between the MAP sensor connector terminal 1 and the ECM connector terminal D8.

Is the problem found?

--

Go to Step 12

Go to Step 14

11

Inspect for a short to voltage in the wire between the MAP sensor connector terminal 2 and the ECM connector terminal A7.

Is the problem found?

--

Go to Step 12

Go to Step 14

12
  1. Repair the wire or the connector terminal as needed.
  2. Clear any DTCs from the ECM.
  3. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

Go to Step 5

13
  1. Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .
  2. Clear any DTCs from the ECM.
  3. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

--

14
  1. Turn the ignition to LOCK.
  2. Replace the ECM. Refer to Engine Control Module Replacement .
  3. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

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