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Tahoe / Yukon Service Manual

DTC P140B or P140C

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5504350 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 P140B Exhaust Gas Recirculation Valve Slow Response - Increasing Flow DTC P140C Exhaust Gas Recirculation Valve Slow Response - Decreasing Flow Circuit/System Description For an overview of the component/system, refer to: Exhaust Gas Recirculation (EGR) System Description

Component Description
Q14A Exhaust Gas Recirculation Valve 1 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.
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.

Conditions for Running the DTC DTCs related to the following system/component = Not Set – B17 Barometric Pressure Sensor – B34 Engine Coolant Temperature Sensor – B66 Intake Air Temperature Sensor – B74 Manifold Absolute Pressure Sensor – B75C Multifunction Intake Air Sensor – B115 Vehicle Speed Sensor – B130 Exhaust Gas Recirculation Temperature Sensor – B131 Exhaust Temperature Sensor No other DTCs related to the concerned component are set. Ambient Air Temperature = Greater than −20°C (−4°F) Barometric Pressure = Greater than 69.6 kPa (10.1 PSI) Desired EGR Position = Greater than 0% Engine = Running Engine Coolant Temperature = 70 to 129°C (158 to 264°F) Fuel Control Loop Status = Closed Loop Ignition and Start Switch Signal = Greater than 11 V Throttle Position = Greater than 85% Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC Exhaust Gas Recirculation Valve = Low/Insufficient Flow — For greater than 5 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type B Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type B 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: – B17 Barometric Pressure Sensor – B34 Engine Coolant Temperature Sensor – B66 Intake Air Temperature Sensor – B74 Manifold Absolute Pressure Sensor – B75C Multifunction Intake Air Sensor – B115 Vehicle Speed Sensor – B130 Exhaust Gas Recirculation Temperature Sensor – B131 Exhaust Temperature Sensor – Q14 Exhaust Gas Recirculation Valve – Q17 Fuel Injector ⇒ If a related DTC is set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If a related DTC is not set
  3. Verify the condition does not exist: Air Cleaner Element — Saturated with water / Restricted Exhaust System — Leaking / Missing components / Restricted » Refer to: Symptoms - Engine Exhaust Induction System — Leaking / Restricted Q20 Intake Air Flow Valve — Binding or Sticking / Restricted ⇒ If a condition exists Repair or replace as necessary ⇓ If no condition exists
  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. 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
  5. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Exhaust Gas Recirculation Valve Replacement - Exhaust Manifold For control module replacement, programming, and setup refer to: Control Module References