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Tahoe / Yukon Service Manual

Cylinder Power Balance Test

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5427453 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 Circuit/System Description This procedure allows the technician to turned off each fuel injector using a scan tool. The change in engine speed or sound, when an injector is turned off, is an indicator how much power that cylinder contributes. If a cylinder generates less power than the others, that indicates a problem with either the compression or the injector. The scan tool control function can also be used to find the cause of a misfire, engine knock, excessive smoke or rough running condition when no relevant DTCs are set. Reference Information Special Tools CH-51450-A Oscilloscope Diagnostic Kit CH-51450-LEAD-A Oscilloscope Basic Lead Kit Equivalent regional tools: Special Tools Circuit/System Verification

  1. Ignition » On / Vehicle » In Service Mode
  2. Verify there are no DTCs set, except DTC P0300–P0306, related to the following system/component: 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. Engine » Idling
  4. Perform the scan tool control function: Cylinder Power Balance » Select » Cylinder 1–6 Injector — One at a time Verify the engine speed or sound changes the same way when turning off each fuel injector. ⇒ If the engine sound does not change the same way for one or more cylinders { Tool Available: CH-51450-A Oscilloscope Diagnostic Kit & CH-51450-LEAD-A Oscilloscope Basic Lead Kit } 4.1. Ignition/Vehicle » Off 4.2. Perform the following procedure/test: Relative Engine Compression Test Verify the procedure/test passes. ⇒ If the procedure/test does not pass » Refer to: Symptoms - Engine Mechanical ⇒ If the procedure/test passes » Replace the appropriate component: Q17 Fuel Injector { Tool Not Available: CH-51450-A Oscilloscope Diagnostic Kit & CH-51450-LEAD-A Oscilloscope Basic Lead Kit } 4.1. Ignition/Vehicle » Off 4.2. Perform the following procedure/test: Engine Compression Test Verify the procedure/test passes. ⇒ If the procedure/test does not pass » Refer to: Symptoms - Engine Mechanical ⇒ If the procedure/test passes » Replace the appropriate component: Q17 Fuel Injector ⇓ If the engine sound changes the same way for all cylinders
  5. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification High Pressure Diesel Fuel Injector Replacement