GMC Yukon 2000–2006

▸Known issuesSingle-cylinder misfire (P0300-P0308) and/or chirp, squeak or tick at camshaft speed: worn cam lobe / lifter, valve or valve spring1

1. Manufacturer communication2002–2006 GMC YUKON DENALI ・ 2023-05-06

   Diagnostic tip: valve, lifter or camshaft issue

   1. 1Fault

      • Noise
      • Warning light
      • P0300
      • P0301
      • P0302
      • P0303
      • P0304
      • P0305
      • Misfire, chirp, squeak, squeal or tick noise, or MIL illuminated.
      • DTCs P0300 (engine misfire detected) and P0301 through P0308 (misfire detected on cylinders 1 through 8) are listed.
      ↓→

   2. 2Finding the cause

      Possible causes

      • Possible causes: worn camshaft lobe and/or lifter roller, a sticking valve, valve leakage, a broken valve spring, or a collapsed AFM lifter.

      Steps to confirm (in the document’s order)

      1. A verified noise is not eliminated by canceling fuel injectors and occurs at camshaft speed (half of crankshaft speed).
      2. If applying pressure to the valve side of the rocker changes the noise, a lifter and/or cam lobe concern on that cylinder is most likely.
      3. Disconnect the coils and injectors on one bank, run the engine with that valve cover removed, back off the rocker arm a couple of turns and listen for a change in the noise.
      4. Measure cam lobe lift at the pushrod side of the rocker arm and compare with other rockers on the same bank; the misfiring or ticking cylinder should have clearly less lift.
      5. A good indicator of a sticking valve is misfires that keep counting on an aggressive deceleration with engine braking.

      1 more points
      ↓→

   3. 3Correction

      Repair

      • If a worn camshaft lobe or lifter roller is found, replace the camshaft and all lifters, and the plastic lifter guide for the affected lifter.

      Caution

      • A damaged cam lobe is easy to overlook through the lifter bores, and unworn lifter rollers do not mean the cam lobes are okay; inspect both carefully.
   Read the sentences of the record

   From the manufacturer’s document

   • Applies to：Applies to GM passenger cars and trucks, 2002 through 2023, with V6/V8 pushrod engines.
   • Condition：Misfire, chirp, squeak, squeal or tick noise, or MIL illuminated.
   • Condition：DTCs P0300 (engine misfire detected) and P0301 through P0308 (misfire detected on cylinders 1 through 8) are listed.
   • Confirm：A verified noise is not eliminated by canceling fuel injectors and occurs at camshaft speed (half of crankshaft speed).
   • Cause：Possible causes: worn camshaft lobe and/or lifter roller, a sticking valve, valve leakage, a broken valve spring, or a collapsed AFM lifter.
   • Confirm：If applying pressure to the valve side of the rocker changes the noise, a lifter and/or cam lobe concern on that cylinder is most likely.
   • Confirm：Disconnect the coils and injectors on one bank, run the engine with that valve cover removed, back off the rocker arm a couple of turns and listen for a change in the noise.
   • Confirm：Measure cam lobe lift at the pushrod side of the rocker arm and compare with other rockers on the same bank; the misfiring or ticking cylinder should have clearly less lift.
   • Caution：A damaged cam lobe is easy to overlook through the lifter bores, and unworn lifter rollers do not mean the cam lobes are okay; inspect both carefully.
   • Repair：If a worn camshaft lobe or lifter roller is found, replace the camshaft and all lifters, and the plastic lifter guide for the affected lifter.
   • Confirm：A good indicator of a sticking valve is misfires that keep counting on an aggressive deceleration with engine braking.
   • Confirm：A broken valve spring may stay stacked together and be hard to see; lightly push on different places on the springs with a small hammer handle.

   Open the manufacturer’s document (PDF) ↗ The points above were read from this document.

   Remedy

   This diagnostic tip bulletin provides additional information on how to diagnose a possible valve, lifter or camshaft issue.