The barometric pressure (BARO) sensor measures the pressure of the atmosphere. This pressure is affected by altitude and weather conditions. A diaphragm within the BARO sensor is displaced by the pressure changes that occur from varying altitudes and weather conditions. The sensor translates this action into electrical resistance. The BARO sensor wiring includes 3 circuits. The BARO sensor and all related circuits are inside the engine control module (ECM). The BARO sensor provides a signal voltage to the ECM, relative to the pressure changes on the BARO sensor signal circuit. The ECM converts the signal voltage input to a pressure value. Changes in BARO due to weather are relatively small, while changes due to altitude are significant. Pressure can range from 56 kPa at an altitude of 4 267 meters (14,000 feet), to 105 kPa at or below sea level. The BARO sensor has a range of 8-207 kPa. The ECM uses the BARO sensor input for fuel delivery and other diagnostics.

P2228

P2229

P2228

The BARO is less than 8 kPa for less than 1 minute.

P2229

The BARO is greater than 199 kPa for less than 1 minute.

DTCs P2228 and P2229 are Type B DTCs.

DTCs P2228 and P2229 are Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools

J 35555 Metal Mityvac

Important: If DTC P0641 or P0651 are set, diagnose those DTCs first. Refer to DTC P0641 or P0651 .

1. Ignition ON, observe the BARO parameter with a scan tool.
2. Compare the BARO value to the range specified in the altitude vs. barometric pressure table.

⇒	The BARO parameter should be within the range specified in the altitude vs. barometric pressure table. Refer to Altitude Versus Barometric Pressure .

3. Engine running, observe the DTC information with a scan tool. DTCs P2228 or P2229 should not set.
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 data.

1. Ignition OFF, disconnect the harness connector at the BARO sensor.
2. Ignition OFF, allow sufficient time for the control module to power down. Measure for less than 5 ohms of resistance between the low reference circuit of the connector and a good 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.

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

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

4. Verify the scan tool BARO sensor voltage parameter is less than 15 kPa.

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

5. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify the scan tool BARO sensor parameter is greater than 190 kPa.

⇒	If less than the specified range, test the sensor signal circuit for an open/high resistance or a short to ground.

6. If all circuits test normal, test the sensor. Refer to Component Testing.

Important: You must perform the Circuit/System Testing before proceeding with the Component Test.

1. Turn ON the ignition with the engine OFF and remove the BARO sensor.
2. Install a 3A fused jumper wire between the 5-volt reference terminal C of the sensor and 5-volt reference.
3. Install a jumper wire between the low reference terminal A of the sensor and ground.
4. Install a jumper wire at the signal terminal B of the BARO sensor.
5. Connect a DMM between the jumper wire from terminal B of the sensor and ground.
6. Install the J 35555 to the BARO sensor vacuum port. Slowly apply vacuum to the sensor while monitoring the voltage on the DMM. The voltage should vary between 5.2-0 volts, without any spikes or dropouts.

⇒	If the voltage is not within the specified range or is erratic, replace the BARO sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.