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Tahoe / Yukon Service Manual

DTC P25BD

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5442984 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 P25BD Unmetered Fuel - Forced Engine Shutdown Circuit/System Description This DTC sets when the control module detects the engine speed increased beyond the desired control limits when no fuel is being delivered. Conditions for Running the DTC Engine Speed = Greater than 1,500 RPM Frequency the DTC runs = Continuously — After the running conditions are met — For greater than 10 s Conditions for Setting the DTC Engine Speed = Greater than 5,200 RPM & Fuel Pressure Regulator = Off — For greater than 1 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC Q17 Fuel Injector — All = Commanded Off Q20 Intake Air Flow Valve = Closed Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC Diagnostic Aids The following condition(s) could cause the DTC to set: Aftermarket equipment/accessories: Exhaust System / Fuel System / Induction System Engine oil overfilled Engine oil sludge build-up. Starting fluid use or alternative fuel added to the engine such as ether. Reference Information DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions 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: B23 Camshaft Position Sensor B26 Crankshaft Position Sensor Q17 Fuel Injector Fuel System ⇒ 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: Engine Oil — Fill Level = Overfull ⇒ If the condition exists 3.1. Ignition/Vehicle » Off 3.2. Verify the following conditions do not exist: Q17 Fuel Injector — Leaking Aftermarket equipment/accessories: Calibration/Software / Fuel System Engine Oil — Contaminated Fuel System — Modified ⇒ If a condition exists » Repair or replace as necessary ⇒ If no condition exists » Refer to: Diagnostic Aids ⇓ If no condition exists
  4. Verify the following conditions do not exist: Positive Crankcase Ventilation Pipe or Positive Crankcase Ventilation Tube — Blocked / Ice / Kinked / Leaking / Restricted / Visible Damage Positive Crankcase Ventilation Valve Orifice — Blocked / Restricted / Visible Damage Positive Crankcase Ventilation Oil Separator — Blocked / Kinked / Leaking / Restricted / Visible Damage ⇒ If a condition exists Repair or replace as necessary ⇓ If no condition exists
  5. Engine » Running
  6. Verify there is no abnormal noise from the component: Engine ⇒ If an abnormal noise is present Refer to: Symptoms - Engine Mechanical ⇓ If no abnormal noise is present
  7. Verify the following conditions do not exist: Excessive engine oil @ Charge Air Cooler Excessive engine oil or Excessive Smoke @ Exhaust System Excessive engine oil @ Induction System / Intake Runners ⇒ If a condition exists Replace the component: Turbocharger ⇓ If no condition exists
  8. 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 Repeat the procedure starting at step 1 ⇓ If the DTC does not set
  9. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification For control module replacement, programming, and setup refer to: Control Module References