For 1990-2009 cars

### Circuit Description

The barometric pressure (BARO) sensor responds to changes in altitude and atmospheric conditions. This gives the engine control module (ECM) an indication of BARO. The ECM 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 ECM 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 ECM on a signal circuit relative to the atmospheric pressure changes. The ECM monitors the BARO sensor signal for a voltage outside of the normal range. If the ECM detects the actual BARO sensor signal is not within a predetermined range of the calculated BARO sensor value, this DTC sets.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2227 Barometric Pressure (BARO) Sensor Performance

### Conditions for Running the DTC

#### Conditions 1

Before the ECM can report DTC P2227 failed, DTCs P2228 and P2229 must run and pass, and last for 0.2 second.

#### Conditions 2

• | Before the ECM can report DTC P2227 failed, DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, P0338, P2228, and P2229 must run and pass.

• | The engine is running for less than 5 seconds.

• | The mass air flow is more than 11 g/s.

• | The pressure ratio is less than 0.75.

• | The EVAP fuel leak detection start-up procedure is not set.

• | DTC P2227 runs continuously once the above conditions are met for 2 seconds.

### Conditions for Setting the DTC

• | The ECM detects that sensor signal is more than 115 kPa.

| OR

• | The ECM detects that sensor signal is less than 42.5 kPa.

| OR

• | The ECM detects that the BARO pressure changed more than 5 kPa within 20 seconds.

• | The ECM detects that the BARO pressure changed more than 30 kPa since the last ignition cycle, and the sum of sensor signal and threshold is less than the calculated pressure.

| OR

• | The ECM detects that the BARO pressure changed more than 30 kPa since the last ignition cycle, and the difference of sensor signal and threshold is more than the calculated pressure.

### 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 4 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

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Front of Vehicle/Engine Compartment Component Views.

• | For an intermittent condition, refer to Intermittent Conditions.

### Test Description

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

1. This step determines if a condition exists.

2. This step is testing the signal circuit. The signal circuit is pulled up to a voltage, so the scan tool should display a voltage within the specified range. If the voltage is low, this indicates the signal circuit is grounded.

3. This step is testing the signal circuit. The signal circuit is pulled up to a voltage. The scan tool should display 0.00 volts when the signal circuit is grounded to the ECM housing with a fused jumper wire. If the voltage displayed on the scan tool is more than the specified value, test the signal circuit of the BARO sensor for an open or a high resistance.

4. The ECM produces a measurable steady-state amperage that provides the 5-volt reference to the BARO sensor. If the amperage on the 5-volt reference circuit is less than the specified value, test the 5-volt reference circuit for an open, a high resistance.

5. This step tests for a high resistance in the low reference circuit of the BARO sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to completely power down.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Component 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 the ignition switch to ON position, with the engine OFF.
2. Clear the diagnostic trouble codes (DTCs) with a scan tool.
3. Start the engine.
4. Observe the DTC information with a scan tool.

Does the DTC fail this ignition?

--

Go to Step 3

Go to Step 4

3 | Is DTC P2228 or P2229 also set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 7
4 |

1. Turn the ignition switch to ON position, with the engine OFF.
2. Observe the BARO sensor parameter on a scan tool while moving the related harness connectors at the barometric pressure (BARO) sensor and at the engine control module (ECM).

Does the BARO parameter remain steady and not change by more than the specified value while a related connector is being moved?

3 kPa

Go to Step 5

Go to Step 17

5 | Observe the BARO sensor parameter on a scan tool while moving the related wiring harnesses. Does the BARO parameter remain steady and not change by more than the specified value while a related wiring harness is being moved? | 3 kPa | Go to Step 6 | Go to Step 18
6 |

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 Records.

Did the DTC fail this ignition?

--

Go to Step 7

Go to Diagnostic Aids

7 | Note: The signal circuit of the BARO sensor is pulled up to a voltage through a 1 mega-ohm resistor.

1. Turn OFF the ignition.
2. Disconnect the BARO sensor.
3. Turn the ignition switch to ON position, with the engine OFF.
4. Observe the BARO Volts parameter with a scan tool.

Is the voltage within the specified range?

4.9-5.2 V

Go to Step 8

Go to Step 12

8 |

1. Connect a fused jumper wire between the signal circuit of the BARO sensor and the ECM housing.
2. Observe the BARO Volts parameter with a scan tool.

Is the voltage at the specified value?

0 V

Go to Step 9

Go to Step 13

9 |

1. Set up a DMM to test amperage on the 400 mA scale.
2. Measure the amperage between the 5-volt reference circuit of the BARO sensor and the ECM housing with a DMM.

Is the amperage more than the specified value?

80 mA

Go to Step 10

Go to Step 11

10 |

1. Turn OFF the ignition.
2. Remove the ECM/TCM fuse from the underhood electrical center.

Caution: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.

3. Measure the resistance between the low reference circuit of the BARO sensor and the ECM housing with a DMM.

Is the resistance more than the specified valve?

5 Ω

Go to Step 14

Go to Step 15

11 |

1. Turn OFF the ignition.
2. Test the 5-volt reference circuit of the BARO sensor for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 16

12 |

1. Turn OFF the ignition.
2. Test the signal circuit of the BARO sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 16

13 |

1. Turn OFF the ignition.
2. Test the signal circuit of the BARO sensor for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 16

14 | Test the low reference circuit of the BARO sensor for an open or a high resistance. Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 16
15 | 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 21 | Go to Step 19
16 | Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20
17 | Repair the damaged connectors and terminals. Refer to Connector Repairs. Did you complete the repair? | -- | Go to Step 21 | --
18 | Repair the affected circuit as necessary. Refer to Wiring Repairs. Did you complete the repair? | -- | Go to Step 21 | --
19 | Replace the BARO sensor. Refer to Barometric Pressure Sensor Replacement. Did you complete the replacement? | -- | Go to Step 21 | --
20 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 21 | --
21 |

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 22

22 | 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