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P2229




DTC P2228 or P2229

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.

DTC Descriptors
DTC P2228
- Barometric Pressure (BARO) Sensor Circuit Low Voltage

DTC P2229
- Barometric Pressure (BARO) Sensor Circuit High Voltage

Diagnostic Fault Information





Typical Scan Tool Data





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 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. 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 0-128 kPa.

Conditions for Running the DTC

* The ignition is ON.
* DTCs P2228 and P2229 run continuously when the above condition is met.

Conditions for Setting the DTC

P2228

The BARO is less than 60 kPa for 1 second.

P2229

The ECM detects that the BARO is greater than 120 kPa for greater than 1 second.

Action Taken When the DTC Sets

DTCs P2228 and P2229 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P2228 and P2229 are Type B DTCs.

Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information
Special Tools

* J 23738-A Mityvac
* J 35555 Metal Mityvac

Circuit/System Verification

1. Verify that the following DTCs are not set: P0641 or P0651.

• If any of the DTCs are set, refer to DTC P0641 or P0651 (Set in ECM) (P0641).

2. Ignition ON, observe the BARO parameter with a scan tool.
3. Compare the BARO value to the range specified in the Altitude vs. Barometric Pressure table.
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.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the BARO sensor.
2. Ignition OFF for 90 seconds, 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.

3. 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.

4. Verify the scan tool BARO sensor voltage parameter is less than 2 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.

5. 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 for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.

6. If all circuits test normal, test or replace the BARO sensor.

Component Testing

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


1. Ignition OFF, remove the BARO sensor.
2. Install a 3A fused jumper wire between the 5-volt reference circuit terminal C and the corresponding terminal of the BARO sensor.
3. Install a jumper wire between the low reference circuit terminal A of the BARO sensor and ground.
4. Install a jumper wire at terminal B of the BARO sensor.
5. Connect a DMM between the jumper wire from terminal B of the BARO sensor and ground.
6. Ignition ON, with the J 23738-A or 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 (Verification Tests) after completing the diagnostic procedure.

* Barometric Pressure Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming

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