GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LF8) 🢒 DTC P2228 or P2229

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 provide 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

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 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.

Conditions for Running the DTC

P2228

    • DTC P2229 is not set.
    • The battery voltage is more than 7 volts.
    • The engine is running.
    • The engine run time is more than 1 second.
    • The key switch is ON for longer than 2 seconds.

P2229

    • DTC P2228 is not set.
    • The battery voltage is between 10-16 volts.
    • The key switch is ON for longer than 2 seconds.
    • The engine is running.
    • The engine run time is more than 1 second.

Conditions for Setting the DTC

P2228

The barometric pressure sensor voltage is less than 1.5 volts.

P2229

The barometric pressure sensor voltage is more than 4.5 volts.

Action Taken When the DTC Sets

DTCs P2228 and P2229 are a Type B DTC.

Conditions for Clearing the DTC

DTCs P2228 and P2229 are 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

Circuit/System Verification

Important: 

   • If DTC P0652 or P0653 are set, diagnose those DTCs first. Refer to DTC P0642 or P0643 .
   • If you cannot duplicate the condition, 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.

  1. Turn ON the ignition with the engine OFF.
  2. 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. ⇒The BARO parameter should be within the range specified in the Altitude vs. Barometric Pressure table.

Circuit/System Testing
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the BARO parameter with a scan tool.
  3. Compare the BARO parameter to the range specified in the Altitude vs. Barometric Pressure table.
    4. ⇒If the BARO parameter is outside the range specified, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming