GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Grand Prix 🢒 DTC 🢒 DTC P0069

Circuit Description

The barometric pressure (BARO) sensor is a transducer that varies resistance according to changes in altitude and atmospheric conditions. This gives the powertrain control module (PCM) an indication the current of barometric pressure. The PCM uses this information to calculate fuel delivery. The BARO sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The PCM supplies 5 volts to the BARO sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The BARO sensor provides a voltage signal to the PCM on a signal circuit relative to the pressure changes. The PCM compares the BARO sensor to the manifold absolute pressure (MAP) sensor in order to monitor the BARO sensor operation. If the difference between the two sensors is more than a predetermined amount, DTC P0069 sets.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0220, P0502, P0503, P2135, P2228, P2229 are not set.
    • The ignition is ON.

Conditions for Setting the DTC
    • The PCM detects that the difference between the BARO sensor pressure and the MAP sensor pressure is more than 5 kPa when the ignition is ON before engine startup.
        OR
    • The difference between the BARO sensor pressure and the PCM predicted BARO is more than 60 kPa when the engine is running.
    • The above conditions are met for 1 second.

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.

Test Description

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

  1. This step tests the ability of the BARO sensor to correctly indicate barometric pressure. The value shown for the BARO sensor varies with altitude and weather conditions.

  2. This step tests the ability of the MAP sensor to correctly indicate barometric pressure.

    3.

  3. This step tests for a sensor that is stuck in range.

    4.

  4. This step calculates the resistance in the 5-volt reference circuit.

    5.

  5. This step calculates the resistance in the low reference circuit.

    6.

  6. This step calculates the resistance in the 5-volt reference circuit.

    7.

  7. This step calculates the resistance in the low reference circuit.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

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

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn ON the ignition, with the engine OFF.
  2. Monitor the DTC information with the scan tool.

Is DTC P0107, P0108, P0641, P0651, P2228, or P2229 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Remove the barometric pressure (BARO) sensor and the manifold absolute pressure (MAP) sensor.
  3. Inspect each sensor for a plugged port.

Did you find and correct the condition?

--

Go to Step 31

Go to Step 4

4

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

Do you have access to another vehicle in which the BARO parameter can be observed with a scan tool?

--

Go to Step 5

Go to Step 6

5

    Important: References to the known good vehicle are made in this step only.

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the BARO parameter with a scan tool.
  3. Turn ON the ignition of the known good vehicle, with the engine OFF.
  4. Observe the BARO parameter of the known good vehicle with a scan tool.
  5. Compare the values.

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

3 kPa

Go to Step 7

Go to Step 12

6

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.

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the BARO parameter with a scan tool. Refer to Altitude Versus Barometric Pressure .
  3. The BARO parameter should be within the range specified for your altitude.

Does the BARO sensor indicate the correct barometric pressure?

--

Go to Step 7

Go to Step 12

7

  1. Observe the BARO parameter and the MAP Sensor parameter with a scan tool.
  2. Compare the values.

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

3 kPa

Go to Step 8

Go to Step 17

8

  1. Turn OFF the ignition.
  2. Connect a J 23738-A Mityvac vacuum pump to the BARO sensor port.
  3. Turn ON the ignition, with the engine OFF.
  4. Monitor the BARO parameter with the scan tool.
  5. Apply vacuum with the J 23738-A SLOWLY 1 inch Hg at a time. Each inch of vacuum should result in a 3-4 kPa drop in the BARO sensor pressure.
  6. Increase the vacuum to 20 inches Hg.

Does the BARO parameter decrease smoothly through the test?

--

Go to Step 9

Go to Step 12

9

Disconnect the J 23738-A from the BARO sensor port.

Does the BARO sensor pressure return to the original value that was observed in step 5 or 6?

--

Go to Step 10

Go to Step 29

10
  1. Turn OFF the ignition.
  2. Remove the MAP sensor from the vacuum source, leaving the harness connected.
  3. Connect a J 23738-A Mityvac vacuum pump to the MAP sensor port.
  4. Turn ON the ignition, with the engine OFF.
  5. Monitor the MAP sensor parameter with the scan tool.
  6. Apply vacuum with the J 23738-A SLOWLY 1 inch Hg at a time. Each inch of vacuum should result in a 3-4 kPa drop in the MAP sensor pressure.
  7. Increase the vacuum to 20 inches Hg.

Does the MAP sensor parameter decrease smoothly through the test?

--

Go to Step 11

Go to Step 17

11

Disconnect the J 23738-A from the MAP sensor port.

Does the MAP sensor pressure return to the original value that was observed in step 7?

--

Go to Intermittent Conditions

Go to Step 28

12

Test for an intermittent and for a poor connection at the BARO 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 31

Go to Step 13

13
  1. Disconnect the BARO sensor harness connector.
  2. Measure the voltage from the 5-volt reference circuit of the BARO sensor to a good ground with a DMM. Note the measurement as "supply voltage."
  3. Connect a test lamp and a DMM in series between the 5-volt reference circuit and the low reference circuit of the BARO sensor at the harness connector.
  4. Measure the amperage with the DMM. Note the measurement as amperage.

Is the amperage at the specified value?

0 mA

Go to Step 21

Go to Step 14

14

  1. Remove the DMM from the circuit.
  2. Connect the test lamp between the 5-volt reference circuit and the low reference circuit of the BARO sensor at the harness connector.
  3. Measure the voltage from the 5-volt reference circuit at the test lamp to a good ground with the DMM. Note the measurement as "load voltage drop."
  4. Subtract the "load voltage drop" from the "supply voltage". Note the result as "supply voltage drop."
  5. Divide the "supply voltage drop" by the amperage.

Is the result more than the specified value?

5 ohms

Go to Step 23

Go to Step 15

15

  1. Measure the voltage from the low reference circuit of the BARO sensor at the test lamp to a good ground with the DMM. Note the result as "low reference voltage drop."
  2. Divide the "low reference voltage drop" by the amperage.

Is the result more than the specified value?

5 ohms

Go to Step 21

Go to Step 16

16
  1. Remove the test lamp.
  2. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the BARO sensor and the signal circuit of the BARO sensor.
  3. Observe the BARO parameter with the scan tool.

Is the pressure more than the specified value?

198 kPa

Go to Step 29

Go to Step 22

17

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 31

Go to Step 18

18

  1. Disconnect the MAP sensor harness connector.
  2. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM. Note the measurement as "supply voltage."
  3. Connect a test lamp and a DMM in series between the 5-volt reference circuit and the low reference circuit of the MAP sensor at the harness connector.
  4. Measure the amperage with the DMM. Note the measurement as amperage.
  5. Remove the DMM from the circuit.
  6. Connect the test lamp between the 5-volt reference circuit and the low reference circuit of the MAP sensor at the harness connector.
  7. Measure the voltage from the 5-volt reference circuit at the test lamp to a good ground with the DMM. Note the measurement as "load voltage drop."
  8. Subtract the "load voltage drop" from the "supply voltage". Note the result as "supply voltage drop."
  9. Divide the "supply voltage drop" by the amperage.

Is the result more than the specified value?

5 ohms

Go to Step 26

Go to Step 19

19

  1. Measure the voltage from the low reference circuit of the MAP sensor at the test lamp to a good ground with the DMM. Note the result as "low reference voltage drop."
  2. Divide the "low reference voltage drop" by the amperage.

Is the result more than the specified value?

5 ohms

Go to Step 24

Go to Step 20

20
  1. Remove the test lamp.
  2. 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 at the harness connector.
  3. Observe the MAP Sensor parameter with the scan tool.

Is the voltage more than the specified value?

4.75 V

Go to Step 28

Go to Step 25

21

Test the low reference circuit of the BARO 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 31

Go to Step 27

22

Test the signal circuit of the BARO 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 31

Go to Step 27

23

Test the 5-volt reference circuit of the BARO 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 31

Go to Step 27

24

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 31

Go to Step 27

25

Test 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 31

Go to Step 27

26

Test the 5-volt reference 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 31

Go to Step 27

27

Test for an intermittent and for a poor connection at the powertrain control module (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 31

Go to Step 30

28

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

Did you complete the replacement?

--

Go to Step 31

--

29

Replace the BARO sensor. Refer to Barometric Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 31

--

30

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 31

--

31
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 32

32

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK