For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P2227: Barometric Pressure (BARO) Sensor Performance
DTC P2228: Barometric Pressure (BARO) Sensor Circuit Low Voltage
DTC P2229: Barometric Pressure (BARO) Sensor Circuit High Voltage

### Circuit/System Description

The barometric pressure (BARO) sensor responds to changes in altitude and atmospheric conditions. This gives the engine control module (ECM) an indication of barometric pressure. The ECM uses this information to calculate fuel delivery. The BARO sensor is located within the controller and is not serviced as a separate unit. The BARO sensor provides a voltage signal to the ECM relative to the atmospheric pressure changes. The ECM monitors the BARO sensor signal for a voltage outside of the normal range.

### Conditions for Running the DTC

#### P2227

• | DTCs P0100, P0101, P0102, P0103, P0121, P0122, P0123, P0221, P0222, P0223, P2228, or P2229 is not set.

• | The engine is operating for greater than 1 second.

• | The mass air flow sensor signal is valid.

• | The evaporative emission (EVAP) leak test is not enabled.

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

#### P2228 or P2229

• | The engine is operating.

• | The DTCs run continuously once the above conditions are met for 2 seconds.

### Conditions for Setting the DTC

#### P2227

• | The ECM detects that the BARO pressure is less than 50 kPa or greater than 115 kPa for greater than 200 ms and DTC P2228 or P2229 is not set.

• | The ECM detects that the BARO pressure changed greater than 10 kPa within 20 seconds.

• | The ECM detects that the BARO pressure changed greater than 30 kPa since the last ignition cycle, and the kPa is less than 2 or greater than 2 kPa of the value predicted by the controller. The condition exists within 5 seconds of engine start up.

• | Any of the condition above exist for 1 second or for a cumulative time of 10 seconds.

#### P2228

The ECM detects that the BARO sensor voltage is less than 0.20 volt for 1 seconds or for a cumulative time of 10 seconds.

#### P2229

The ECM detects that the BARO sensor voltage is greater than 4.87 volts for 1 seconds or for a cumulative time of 10 seconds.

### Action Taken When the DTC Sets

DTCs P2227, P2228, and P2229 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P2227, P2228, and P2229 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Start the engine. Observe the DTC information with a scan tool. DTCs P2227, P2228, or P2229 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Inspect the atmospheric vent on the ECM case for one of the following conditions:

• | Moisture in the vent inlet

• | Debris in the vent inlet

⇒ | If a condition exists, attempt to clean or dry the atmospheric inlet.

2. Start the engine. Observe the DTC information with a scan tool. DTCs P2227, P2228, or P2229 should not set.

⇒ | If DTC P2227, P2228, or P2229 sets, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming