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HOMESERVICE MANUALSGMC2020ACADIA SLE, 2.5L ENG VIN AREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 239 (ENGINE CONTROLS AND FUEL - 2.0L (LSY) - DIAGNOSTIC INFORMATION AND PROCEDURES (2 OF 2))DIAGNOSTIC INFORMATION AND PROCEDURESRELATIVE ENGINE COMPRESSION TESTCIRCUIT/SYSTEM TESTING
2020 GMC Acadia SLE, 2.5L Eng VIN A

Circuit/System Testing

2020 GMC Acadia SLE, 2.5L Eng VIN ASECTION Circuit/System Testing
WARNING: This page is about a different car, the 2021 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle - Off
  2. Apply - Parking Brake
  3. Install - CH-51450-A Oscilloscope Diagnostic Kit & CH-51450-LEAD-A Oscilloscope Basic Lead Kit
    1. Channel A Lead: Blue @ Oscilloscope
    2. Channel A Lead: Blue @ B+ & Ground
      NOTE:

      Hover the mouse cursor over an icon button to display the button's description.

  4. Coupling - DC
  5. Select: Connect Detect

    Verify the following information is correctly displayed: Connected Channels = Green

    • If the information is not correctly displayed 

      Repair the poor connection & Repeat this step

    • Go to next step: If the information is correctly displayed 
  6. Setup - CH-51450-A Oscilloscope Diagnostic Kit & CH-51450-LEAD-A Oscilloscope Basic Lead Kit
    1. Select: Automotive
    2. Select: Charging and Starting
    3. Select: Relative Compression
    4. Select: Voltage
  7. Select: Start Capturing
  8. Perform the following action:
      NOTE:

      Make sure the component is not obstructed: Accelerator Pedal

    1. Fully Applied - Accelerator Pedal - Wide Open Throttle
    2. {Automatic Transmission} Apply & Hold - Brake Pedal

      {Manual Transmission} Apply & Hold - Clutch Pedal

    3. Engine - Cranking - For 5 - 10 s
    4. Select: Stop Capturing

      Verify the following information is correctly displayed: The waveform valleys are all even. Refer to Oscilloscope Waveform Library

    • If the information is not correctly displayed 

      Verify the condition does not exist with the component and repair as necessary:

      NOTE:

      The following are examples of what could cause compression issues. Inspect all mechanical components for the applicable cylinder. The list is not all encompassing. Refer to Symptoms - Engine Mechanical

    • Camshaft Lobe(s) - Visible Damage/Worn
    • Exhaust Valve or Intake Valve - Stuck Open/Visible Damage
    • Exhaust Valve Seat or Intake Valve Seat - Visible Damage
    • Piston - Cracked/Visible Damage
    • Piston Ring - Seized/Visible Damage/Worn
    • Valve Lifter - Visible Damage/Worn
    • Valve Spring - Visible Damage/Worn
    • Valve Rocker Arm - Visible Damage/Worn
    • Go to next step: If the information is correctly displayed 
  9. All OK.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.