For 1990-2009 cars

### 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 the 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 low, DTC P2228 sets.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2228 Barometric Pressure (BARO) Sensor Circuit Low Voltage

### Conditions for Running the DTC

• | The ignition is ON.

| OR

| The engine is cranking or running.

• | This DTC runs continuously within the enabling conditions.

### Conditions for Setting the DTC

• | The PCM detects that the BARO is less than 50 kPa for more than 8 seconds.

| OR

• | The PCM detects that the BARO signal voltage is less than 0.51 volt for more than 8 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.

### Test Description

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

1. The BARO sensor 5-volt reference circuit is shared with other sensors. If DTC P0641 is set, this indicates a shorted 5-volt reference circuit or a shorted component and should be diagnosed first.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn ON the ignition, with the engine OFF.
2. Observe the DTC Information with a scan tool.

Is DTC P0641 set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3 | Observe the BARO parameter with a scan tool. Is the BARO parameter less than the specified value? | 0.51 V | 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 90 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 5

Go to Testing for Intermittent Conditions and Poor Connections

5 | Important: The connectors for the following sensors are of the same configuration, but are not interchangeable.

1. Observe the engine controls schematics for the barometric pressure (BARO) sensor and for the supercharger inlet pressure (SCIP) sensor and note the circuit colors.
2. Inspect the wiring harness of the BARO sensor for the proper connection.
3. Inspect the wiring harness of the SCIP sensor for the proper connection.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 6

6 | 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 . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 7
7 |

1. Disconnect the BARO sensor electrical connector.
2. Turn ON the ignition, with the engine OFF.
3. Measure the voltage from the 5-volt reference circuit of the BARO sensor to a good ground with a DMM.

Is the voltage more than the specified value?

4.8 V

Go to Step 8

Go to Step 9

8 |

1. 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.
2. Observe the BARO parameter with the scan tool.

Is the BARO parameter more than the specified value?

4.8 V

Go to Step 12

Go to Step 10

9 | Test the 5-volt reference circuit of the BARO sensor for an open. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11
10 | Test the signal circuit of the BARO sensor for an open or a short to ground. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11
11 | 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 . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13
12 | Replace the BARO sensor. Refer to Barometric Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
13 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 14 | --
14 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 90 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 15

15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK