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

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
5-Volt Reference | P0642, P2228 | P2227 | P2228 | P0643, P2229 | P2227
BARO Sensor Signal | P2228 | P2227 | P2228 | P2229 | P2227
Low Reference | -- | P2227 | P2229 | -- | --

### Typical Scan Tool Data

#### BARO Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The ignition is ON, or the engine is running. Parameter Normal Range: 60-104 kPa, varies with the altitude.
5-Volt Reference | 0 kPa | 0 kPa | 0 kPa
BARO Sensor Signal | 0 kPa | 0 kPa | 127 kPa
Low Reference | -- | 127 kPa | --

### Circuit/System Description

The barometric pressure (BARO) sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The engine control module (ECM) supplies 5 volts to the BARO sensor on the 5-volt reference circuit, and provides a ground for the low reference circuit. The BARO sensor provides a voltage signal to the ECM on the signal circuit relative to the changes in pressure caused by the changes in vehicle altitude.

The purpose of the performance portion of the diagnostic is to analyze the performance of the BARO sensor by comparing the response and the range of the sensor signal to two distinct models under various operating conditions.

• | The gradient portion of the model looks for changes in BARO that are not within range of a normal plausible rate of change.

• | The second portion of the model compares the measured BARO to a calculated BARO.

| Both models use various parts of the information derived from the following inputs:

- | A calculated intake manifold pressure

- | BARO

- | BARO from the previous drive cycle

- | Camshaft phasing

- | Distance driven

- | Engine coolant temperature (ECT)

- | Engine load

- | Engine speed

- | Mass air flow (MAF)

- | Throttle position (TP)

- | Vehicle speed (VS)

### Conditions for Running the DTC

#### P2227--Gradient Model Test

• | DTCs P000A, P000B, P0016, P0017, P0102, P0103, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, P0340, P0341, P0365, P0366, P0501, P0642, P0643, P0652, P0653, P2228, or P2229 is not set.

• | The ignition is ON, or the engine is running.

• | This model of the DTC runs continuously within the enabling conditions.

#### P2227--BARO versus Calculated BARO Test

• | DTCs P000A, P000B, P0016, P0017, P0102, P0103, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, P0340, P0341, P0365, P0366, P0501, P0642, P0643, P0652, P0653, P2228, or P2229 is not set.

• | DTCs P0068 has ran and passed.

• | The calculated intake manifold pressure is less than 50 kPa.

• | The ECM has powered down from the previous drive cycle.

• | The ECM is not in decel fuel cutoff.

• | The ECT is warmer than 40°C (104°F).

• | The MAF is less than 18 kg/h.

• | The VS is less than 10 km/h (6 mph)

• | The above conditions are met for greater than 13 seconds.

• | This DTC runs once per drive cycle within the enabling conditions.

#### P2228

• | DTC P0642, P0643, P0652, P0653, or P2227 is not set.

• | The ignition is ON, or the engine is running.

• | The ignition voltage is greater than 9 volts.

• | This DTC runs continuously within the enabling conditions.

#### P2229

• | The ignition is ON, or the engine is running.

• | The ignition voltage is greater than 9 volts.

• | This DTC runs continuously within the enabling conditions.

### Conditions for Setting the DTC

#### P2227-Gradient Model Test

The ECM detects a rate of change in the BARO of greater than one kPa/s for more than 3 seconds.

#### P2227-BARO versus Calculated BARO Test

• | The ECM detects that the difference in BARO between the previous drive cycle and the current drive cycle is greater than 20 kPa.

| AND

• | The ECM detects that the BARO sensor signal is not within a calibrated range of the model for greater than 3 seconds.

#### P2228

The ECM detects a BARO of less than 51 kPa.

#### P2229

The ECM detects a BARO of greater than 109 kPa.

### 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

Altitude Versus Barometric Pressure

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

#### Special Tools

• | J 23738-A Mityvac

• | J 35555 Metal Mityvac

### Circuit/System Verification

1. Verify that DTC P0642, P0643, P0652, or P0653 is not set.

⇒ | If any of the DTCs are set, refer to DTC P0642, P0643, P0652, or P0653.

2. Ignition OFF for 90 seconds, determine the current vehicle testing altitude.
3. Ignition ON, engine OFF, observe the scan tool BARO Sensor parameter. Compare the parameter to the Altitude Versus Barometric Pressure table. The parameter should be within the specified range as indicated in the table.
4. 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 sensor for any damage.
2. Inspect for contamination buildup at or inside of the BARO port.
3. In cold climates, inspect for any snow or ice buildup at or inside of the BARO port.
4. Ignition OFF for 90 seconds, disconnect the harness connector at the BARO sensor.
5. Test for less than 5 ohms between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

6. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.

⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

7. Verify the scan tool BARO Sensor parameter is less than 1 kPa.

⇒ | If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the ECM.

8. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 1. Verify the scan tool BARO Sensor parameter is greater than 126 kPa.

⇒ | If less than the specified range, test the signal circuit terminal 3 for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

9. If the circuits test normal, test or replace the BARO sensor.

### Component Testing

Important: You must perform the Circuit/System Testing in order to verify the integrity of the BARO sensor circuits before proceeding with the Component Testing.

#### Skewed Sensor Test

1. Using the following steps and referencing the table below will determine if the MAP sensor is skewed.
2. Ignition ON, engine OFF, observe the MAP sensor scan tool parameter.
3. Use the observed MAP Sensor Scan Tool parameter that is closest to a value that is indicated in the first column.

THEN

4. Using the J 23738-A or the J 35555 to apply 5 in Hg of vacuum to the MAP sensor, the parameter in the first column should decrease by 17 kPa. The acceptable range is indicated in the second column.
5. Using the J 23738-A or the J 35555 to apply 10 in Hg of vacuum to the MAP sensor, the parameter in the first column should decrease by 34 kPa.. The acceptable range is indicated in the third column.
6. Substract the third MAP sensor reading from the first MAP sensor reading. Verify that the vacuum decrease is within 1 in Hg (4 kPa) of the applied vacuum.

⇒ | If the vacuum decrease is not within the specified range, replace the MAP sensor.

#### Skewed Signal Test

1. Using the following steps and referencing the table below will determine if the BARO sensor is skewed.
2. Ignition ON, engine OFF, observe the BARO Sensor Scan Tool parameter.
3. Use the observed BARO Sensor Scan Tool parameter that is closest to a value that is indicated in the first column.

THEN

4. Using the J 23738-A or the J 35555 to apply 5 in Hg of vacuum to the BARO sensor, the parameter in the first column should decrease by 17 kPa. The acceptable range is indicated in the second column.
5. Using the J 23738-A or the J 35555 to apply 10 in Hg of vacuum to the BARO sensor, the parameter in the first column should decrease by 34 kPa. The acceptable range is indicated in the third column.

Ignition ON, Engine OFF, BARO Sensor Parameter | BARO Sensor Parameter With 5 Inches of Vacuum Applied | BARO Sensor Parameter With 10 Inches of Vacuum Applied
--- | --- | ---
100 kPa | 79-87 kPa | 62-70 kPa
95 kPa | 74-82 kPa | 57-65 kPa
90 kPa | 69-77 kPa | 52-60 kPa
80 kPa | 59-67 kPa | 42-50 kPa
70 kPa | 49-57 kPa | 32-40 kPa
60 kPa | 39-47 kPa | 22-30 kPa

#### Erratic Signal Test

1. Ignition OFF, install a 3A fused jumper wire between the 5-volt reference circuit terminal 1 and the corresponding terminal of the BARO sensor.
2. Install a jumper wire between the low reference circuit terminal 2 of the BARO sensor and ground.
3. Install a jumper wire at terminal 3 of the BARO sensor.
4. Connect a DMM between the jumper wire from terminal 3 of the BARO sensor and ground.
5. Ignition ON, with the J 23738-A or the J 35555 , slowly apply vacuum to the sensor while observing the voltage on the DMM. The voltage should vary between 0-5.2 volts, without any spikes or dropouts.

⇒ | If the voltage reading is erratic, replace the BARO sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming