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Tahoe / Yukon Service Manual

DTC P034F, P0404, or P042E

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5905749 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 P034F Cold Start Exhaust Gas Recirculation Valve Open Position Performance DTC P0404 Exhaust Gas Recirculation Valve Open Position Performance DTC P042E Exhaust Gas Recirculation Valve Closed Position Performance Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Control — Terminal 4 P0404 P0403 P0490 —
Control — Terminal 5 P0404 P0403 P0490 —

Circuit/System Description For an overview of the component/system, refer to: Exhaust Gas Recirculation (EGR) System Description

Circuit Description
Control — Terminal 4 The output circuit is switched from ground to 12 V to activate the component.
Control — Terminal 5 The output circuit is switched from ground to 12 V to activate the component.
Component Description
Q14 Exhaust Gas Recirculation Valve 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
Component Description
resistance proportionally with the position of the component/system: EGR Valve
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.

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 P034F DTCs related to the following system/component = Not Set – B9 Ambient Air Temperature Sensor – B34 Engine Coolant Temperature Sensor – Q14 Exhaust Gas Recirculation Valve — Circuit DTCs – Exhaust Gas Recirculation Valve Position Sensor ECT Sensor = Warmer than 0°C (32°F) Engine = Running Ignition and Start Signal = Greater than 11 V P0404, P042E DTC P262B = Not set DTCs related to the following system/component = Not Set – B34 Engine Coolant Temperature Sensor – Q14 Exhaust Gas Recirculation Valve — Circuit DTCs Ambient Air Temperature = Warmer than -60°C (-76°F) Engine = Running Engine Coolant Temperature = Warmer than 60°C (140°F) Ignition and Start Signal = Greater than 11 V Frequency the DTC runs = Continuously — After the running conditions are met — For greater than 7.5 s Conditions for Setting the DTC Exhaust Gas Recirculation Valve = Commanded state does not match the actual state — For greater than 2.5 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC — Exceptions listed below Warning Message = Service Emission System / Service Exhaust Fluid System Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC — Exceptions listed below DTC P034F = Type B DTC 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 the scan tool parameter: Exhaust Gas Recirculation Valve = 5 to 95% ⇒ If not in the specified range Refer to: DTC P0405, P0406, or U0651 ⇓ If in the specified range
  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 Refer to: Circuit/System Testing ⇓ If the DTC does not set
  4. All OK. Circuit/System Testing
  5. Verify a condition does not exist with the component: Q14A Exhaust Gas Recirculation Valve 1 Stuck Debris on the component. Coking ⇒ If a condition exists Repair or replace as necessary ⇓ If no condition exists
  6. Ignition/Vehicle & All vehicle systems » Off
  7. Disconnect the electrical connector: Q14A Exhaust Gas Recirculation Valve 1
  8. Disconnect the electrical connector: K20 Engine Control Module
  9. Ignition » On / Vehicle » In Service Mode
  10. Test for less than 1 V between the test points: Control circuit terminal 5 @ Component harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇓ If less than 1 V
  11. Test for infinite resistance between the test points: Control circuit terminal 5 @ Component harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If infinite resistance
  12. Test for less than 2 Ω between the test points: Control circuit terminal 5 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇓ If less than 2 Ω
  13. Test for less than 1 V between the test points: Control circuit terminal 4 @ Component harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇓ If less than 1 V
  14. Test for infinite resistance between the test points: Control circuit terminal 4 @ Component harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If infinite resistance
  15. Test for less than 2 Ω between the test points: Control circuit terminal 4 @ Component harness & The other end of the circuit k@ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇓ If less than 2 Ω
  16. Replace the component: Q14A Exhaust Gas Recirculation Valve 1
  17. 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: K20 Engine Control Module ⇓ If the DTC is not set
  18. 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