GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.8L (L26 and L32) 🢒 DTC P2229

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 of the current 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 monitors the BARO sensor signal for voltage outside of the normal range. If the PCM detects a BARO sensor signal voltage that is excessively high, DTC P2229 sets.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The PCM detects that the BARO sensor pressure is more than 176 kPa for 10 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.

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 P0651 also set?

--

Go to DTC P0651

Go to Step  3

3
  1. Start the engine.
  2. Observe the BARO sensor parameter with a scan tool.

Is the pressure more than the specified value?

176 kPa

Go to Step 5

Go to Step 4

4

  1. Observe the Freeze Frame/Failure Records for this DTC.
  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 Record.

Does the DTC fail this ignition?

--

Go to Step 5

Go to Intermittent Conditions

5
  1. Disconnect the barometric pressure (BARO) sensor electrical connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the BARO sensor parameter with the scan tool.

Is the pressure less than the specified value?

10 kPa

Go to Step 6

Go to Step 7

6
  1. Turn OFF the ignition.
  2. Connect a jumper wire between each of the terminals in the BARO sensor harness connector and the corresponding terminal at the BARO sensor. Refer to Using Connector Test Adapters in Wiring Systems.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the low reference circuit of the BARO 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 8

Go to Step  9

7

Test the BARO sensor signal circuit between the powertrain control module (PCM) and the BARO 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 13

Go to Step 12

8

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

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

9

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 13

Go to Step 11

10

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 13

Go to Step 12

11

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

Did you complete the replacement?

--

Go to Step 13

--

12

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13
  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 14

14

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