GM Service Manual Online
For 1990-2009 cars only

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 Descriptor

DTC P2227 : Barometric Pressure (BARO) Sensor Performance

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

5-Volt Reference Circuit

P0641, P2228

P0069

P0069, P2228

P0069, P0641

P2227

BARO Sensor Signal Circuit

P2228

P0069

P0069, P2228

P0069, P2229

P2227

Low Reference Circuit

--

P0069

P0069, P2227, P2229

--

P2227

Typical Scan Tool Data

BARO Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: The Ignition is ON

Parameter Normal Range: BARO

5-Volt Reference Circuit

8-10 kPa

8-10 kPa

200-208 kPa

BARO Sensor Signal Circuit

8-10 kPa

8-10 kPa

200-208 kPa

Low Reference Circuit

--

191 kPa

--

Circuit/System Description

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 diaphragm action into the voltage signal input that is used by the engine control module (ECM) for diagnostics, emissions control, and to calculate fuel delivery.

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 104 kPa at or below sea level. The BARO sensor has a 5-volt reference circuit, a low reference circuit and a signal circuit. The BARO sensor provides a voltage signal to the ECM on a signal circuit relative to barometric pressure changes.

Conditions for Running the DTC

    • DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0128, P0220, P0502, P0503, P2135, P2228, P2229 are not set.
    • The engine run time is greater than 10 seconds.

Conditions for Setting the DTC

The ECM detects that 80 out of 100 consecutive BARO sensor samples vary greater than 10 kPa between each sample, for 10 seconds.

Action Taken When the DTC Sets

DTC P2227 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P2227 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

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 35555 Metal Mityvac

Circuit/System Verification

  1. Ignition ON, observe the scan tool MAP, SC Inlet Pressure, and BARO sensor parameters. The readings should be within 5 kPa of each other and also the current BARO for your location. Refer to Altitude Versus Barometric Pressure.
  2. Operate the vehicle within the Conditions for Running the DTC to verify that 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

Engine running, monitor the BARO parameter with the scan tool for a steady value.

If the BARO parameter is not a steady value, test the BARO circuit for an intermittent short or open. If all circuits test normal, replace the BARO sensor.

Component Testing

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

  1. Ignition ON, engine OFF, 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.
  7. If the voltage is not within the specified range or 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
    •  Barometric Pressure Sensor Replacement