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Tahoe / Yukon Service Manual

DTC P131D, P131E, P1385, or P1386

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5504345 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 P131D Exhaust Pressure Regulator Valve Control At Limit – High Pressure DTC P131E Exhaust Pressure Regulator Valve Control At Limit – Low Pressure DTC P1385 Exhaust Pressure Control Valve Control At Limit - Pressure Too High During Cold Start DTC P1386 Exhaust Pressure Control Valve Control At Limit - Pressure Too Low During Cold Start Circuit/System Description The engine control module can not directly measure the amount of recirculated exhaust gases. To verify the correct operation of the recirculation system, it uses a compare between the fresh air that was measured by the mass air flow sensor and the calculated amount that the engine is expected to suck in. The difference is the amount of recirculated exhaust. For an overview of the component/system, refer to: Exhaust Gas Recirculation (EGR) System Description Conditions for Running the DTC P131D, P131E Engine = Running Ignition and Start Switch Signal = Greater than 11 V Frequency the DTC runs = Continuously — After the running conditions are met — For greater than 12 s P1385, P1386 DTCs related to the following system/component = Not Set B34 Engine Coolant Temperature Sensor Ambient Air Temperature = Warmer than -7°C (19°F) Barometric Pressure = Greater than 76 kPa (11 PSI) Engine = Running Ignition and Start Switch Signal = Greater than 11 V Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC EGR Differential Pressure Sensor = Not within a calibrated range — For greater than 12 s A ti T k Wh th DTC S t Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type B DTC Conditions for Clearing the DTC P0401 DTCs listed in the DTC Descriptor category = Type B DTC Reference Information DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Circuit/System Verification

  1. Verify there are no DTCs set related to the following component/system: B34 Engine Coolant Temperature Sensor ⇒ If a related DTC is set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If a related DTC is not set
  2. Verify the following conditions do not exist: Exhaust Gas Recirculation Valve Cooler — Restricted Exhaust Gas Recirculation Valve 2 — Binding or Sticking / Restricted / Visible Damage Exhaust Pressure Control Valve — Binding or Sticking / Restricted Exhaust Gas Recirculation System — Leaking / Restricted ⇒ If a condition exists Repair or replace as necessary ⇓ If no condition exists
  3. Clear the DTCs.
  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.
  5. Verify the DTC does not set. ⇒ If the DTC sets Replace the component: M122 Exhaust Pressure Regulator Valve ⇓ If no DTC is set
  6. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Exhaust Back Pressure Valve Replacement — M122 Exhaust Pressure Regulator Valve