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Tahoe / Yukon Service Manual

DTC P049D

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5471221 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P049D Exhaust Gas Recirculation Valve Position Not Learned Circuit/System Description For an overview of the component/system, refer to: Exhaust Gas Recirculation (EGR) System Description

Component Description
K20 Engine Control Module The control module contains a microprocessor used to process input data to control outputs. The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.
Q14A Exhaust Gas Recirculation Valve 1 The assembly has several functions: Exhaust Gas Recirculation Valve — A solenoid valve is an electro-mechanically operated valve. The valve is controlled by an electric current through the solenoid. EGR Position Sensor — The component contains 1 potentiometer(s) that varies its resistance proportionally with the position of the component/system: EGR Valve

Redirecting the exhaust gas back into the intake system aids in reducing the amount of oxygen that enters the cylinders. This reduces the amount of nitrogen oxide (NOx) that is produced during combustion. The component is actuated by a bidirectional DC motor. Conditions for Running the DTC DTC P262B = Not set DTCs related to the following system/component = Not Set – B34 Engine Coolant Temperature Sensor – B75C Multifunction Intake Air Sensor – B115 Vehicle Speed Sensor No other DTCs related to the concerned component are set. Engine Coolant Temperature Sensor = 30 to 150°C (86 to 302°F) Ignition and Start Signal = Greater than 9.5 V Frequency the DTC runs = Once — Per ignition cycle — After ignition Off Conditions for Setting the DTC Exhaust Gas Recirculation Valve = Commanded state does not match the actual state Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List 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 Circuit/System Verification

  1. Ignition » On / Vehicle » In Service Mode
  2. Verify there are no DTCs set related to the following component/system: B34 Engine Coolant Temperature Sensor B75 Mass Airflow Sensor B115 Vehicle Speed Sensor Q14A Exhaust Gas Recirculation Valve 1 ⇒ If a related DTC is set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If a related DTC is not set
  3. 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. Verify the DTC does not set. ⇒ If the DTC sets Replace the component: Q14A Exhaust Gas Recirculation Valve 1 ⇓ If the DTC does not set
  4. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Exhaust Gas Recirculation Valve Replacement - Exhaust Manifold — Q14A Exhaust Gas Recirculation Valve 1 For control module replacement, programming, and setup refer to: Control Module References