P0308 on 2021 Cadillac Escalade 6.2L V8: Cylinder 8 Misfire Causes and Fixes

What's Unique About the 2021-2021 Cadillac ESCALADE NA

The 2021 Escalade's 6.2L L87 V8 engine uses a Dynamic Fuel Management (DFM) system to improve fuel economy by deactivating cylinders. Unfortunately, the complex hydraulic valve lifters used for this system are a well-documented weak point and are prone to premature failure, often due to a broken internal locking pin spring. A collapsed or stuck lifter is a very common cause for a P0308 misfire on this specific engine, making diagnosis more critical as it's a major internal engine repair, not a simple tune-up. This issue is so common it has led to GM service updates (N212353840) and class-action lawsuits. 🎬 Watch: Learn more about the DFM lifter class action lawsuit. Additionally, some 2021 models built between June and October 2020 were subject to a service bulletin for faulty valve springs which could also cause misfires.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Flashing or solid Check Engine Light
• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• A distinct ticking or knocking noise from the engine, especially from the passenger side.
• Service StabiliTrak message on the dashboard.
• Fuel smell from the exhaust.

Most Likely Causes

1. Failed Valve Lifter 🔴 High Probability The 6.2L L87 engine has a widely documented issue with its Dynamic Fuel Management (DFM) lifters. The internal locking pin spring can break, causing the lifter to collapse or become stuck, leading to a misfire. This is addressed in GM Technical Service Bulletin #23-NA-043 and Service Update #N212353840.
   How to confirm: Listen for a distinct ticking or knocking noise from the top of the engine. A professional diagnosis involves removing the valve covers to inspect the valve train components, specifically looking for a rocker arm on cylinder 8 that is not moving. A compression test will likely show low or zero compression on cylinder 8. A borescope can also be used to inspect the lifter and camshaft lobe for damage.
   Typical fix: This is a significant repair. Per TSB #23-NA-043, if the vehicle has under 16,000 miles, GM recommends replacing all lifters and guides on both banks. For vehicles over 16,000 miles, the recommendation is to replace them on the affected bank only. The repair requires removing the cylinder head and also replacing the head gasket, head bolts, intake gaskets, and often the bent pushrod associated with the failed lifter. If the camshaft is damaged, it must also be replaced.
   Est. part cost: $500-$1600
2. Faulty Ignition Coil 🟡 Medium Probability → Shop Ignition Coil
   How to confirm: Swap the ignition coil from cylinder 8 with another cylinder (e.g., cylinder 6, which is next to it on the same bank). Clear the codes and drive the vehicle. If the misfire code changes to P0306, the ignition coil is faulty. Resistance can also be checked: primary resistance should be ~0.450 - 0.660 ohms and secondary resistance should be ~6.1K - 8.22K ohms.
   Typical fix: Replace the faulty ignition coil (OEM Part #12658183). It is often recommended to replace the corresponding spark plug at the same time.
   Est. part cost: $45-$90
3. Worn or Fouled Spark Plug 🟡 Medium Probability → Shop Spark Plug
   How to confirm: After confirming the coil is good, remove the spark plug from cylinder 8. Inspect it for signs of wear, carbon fouling, oil, or coolant. A damaged, wet, or worn plug can't produce a strong spark. The specified gap is typically 0.040 inches.
   Typical fix: Replace the spark plug. It's best practice to replace all 8 spark plugs at the same time for balanced engine performance. The OEM recommended part is an ACDelco Iridium plug, part number 41-114 (GM #12622441).
   Est. part cost: $8-$25
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector The L87 uses a direct injection system, and injectors can fail, though it's less common than lifter or ignition issues.
   How to confirm: A fuel injector balance test can be performed with a professional scan tool (like GM's GDS2) to see if the injector is flowing correctly. You can also listen to the injector with a mechanic's stethoscope; it should have a consistent clicking sound. Swapping injectors is a complex job on this direct-injected engine.
   Typical fix: Replace the fuel injector for cylinder 8. This is a more involved job than on port-injected engines as it requires removing the intake manifold.
   Est. part cost: $70-$150

Rare But Worth Checking

• Internal Coolant Leak (Head Gasket): A leaking heater hose connection located directly above the cylinder 8 ignition coil can cause coolant to seep into the spark plug well, shorting the connection. More seriously, a failed head gasket can cause coolant to enter the cylinder, fouling the spark plug and causing a misfire, which would be confirmed with a cylinder leak-down test.
• Bent Pushrod: A failed lifter almost always results in a bent pushrod for that cylinder, as the collapsed lifter creates excessive slack in the valvetrain. TSB #23-NA-043 mentions this as a related failure. This is discovered during the inspection for a failed lifter.
• Connecting Rod Bearing Failure: A major recall (N252494001) was issued for 2021-2024 L87 engines due to manufacturing defects in the connecting rod bearings that can lead to engine seizure. While the primary symptom is often catastrophic failure, early stages of bearing wear could potentially cause crankshaft speed variations that might be interpreted as a misfire.
• Broken Valve Spring: A GM service bulletin was issued for 2021 L87 engines built between June 1, 2020, and October 7, 2020, for faulty valve springs. A broken spring will cause a persistent misfire, ticking noise, and a loss of compression in the affected cylinder.

Diagnosis Steps

1. Read the code with an OBD-II scanner and confirm P0308 is present. Note any other codes (like P0300 or P050D) and review freeze-frame data.
2. Listen carefully for any ticking or knocking noises from the engine bay, particularly from the passenger side valve cover area. A distinct tick strongly points towards a mechanical issue like a failed lifter.
3. If no noise is present, perform a simple diagnostic swap. Switch the ignition coil from cylinder 8 with cylinder 6. Clear the codes and see if the misfire moves to P0306. If it does, the coil is bad.
4. If the misfire stays on cylinder 8, inspect and then swap the spark plug from cylinder 8 with another cylinder. If the code moves, the spark plug is bad.
5. If the misfire remains on cylinder 8, use a scan tool with Mode $06 data to monitor live misfire counts to confirm the fault is still present.
6. If ignition components are ruled out, a mechanical or fuel issue is likely. Perform a compression test on cylinder 8. A low or zero reading strongly suggests a mechanical fault like a failed lifter or bent pushrod.
7. If compression is good, the issue could be fuel-related. A professional can perform a fuel injector balance test.
8. Given the high probability of lifter failure, if a mechanical fault is suspected (ticking noise or low compression), the next step is professional diagnosis involving removal of the valve cover to inspect the pushrods, rocker arms, and valve springs for cylinder 8.

Parts You'll Likely Need

• Valve Lifter Kit (DFM) (OEM #12710735 (Kit for one bank), 12698945 (Superseded lifter part number)) — This is the most probable serious failure on the 6.2L L87 engine causing a P0308. The repair involves replacing all lifters on at least one bank.
  Trusted brands: ACDelco, General Motors
  OEM price range: $400-$800
  Aftermarket price range: $300-$600
• Ignition Coil (OEM #12658183) — An ignition coil is a common failure point for single-cylinder misfires and an easy diagnostic swap.
  Trusted brands: ACDelco, NGK, Delphi
  OEM price range: $60-$90
  Aftermarket price range: $45-$70
• Spark Plug (OEM #41-114 (GM #12622441)) — A worn or fouled spark plug is a common and simple cause of a misfire.
  Trusted brands: ACDelco, NGK
  OEM price range: $12-$20
  Aftermarket price range: $8-$15
• Head Gasket & Bolt Set — Required for the lifter replacement job, as the cylinder head must be removed.
  Trusted brands: ACDelco, Fel-Pro
  OEM price range: $150-$250
  Aftermarket price range: $100-$200

Related Codes That Often Appear With This One

• P0300 — This is a code for random or multiple misfires. It often appears alongside a specific cylinder misfire code like P0308, especially if the underlying cause (like a failing lifter) is beginning to affect other cylinders or cause general engine instability.
• P050D — This code indicates a rough idle during a cold start. TSB #PIP5628G directly links this code with misfires (P0300-P0308) on this platform, suggesting a common root cause, often related to cold engine operation and potential lifter issues.

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-043: Acknowledges that an internal lifter concern can cause misfire codes P0300-P0308 and provides repair guidance, including replacing lifters on one or both banks depending on mileage.
• PIP5628G: A diagnostic aid for technicians encountering misfire codes P0300-P0308 and/or cold start rough idle code P050D, guiding them through a checklist of potential causes.
• N212353840: A GM Service Update specifically for 2021 models addressing broken valve lifter lock pin springs, a direct cause of lifter failure and misfires.

Platform-Specific Known Issues

• Widespread DFM Lifter Failure: → Shop Engine Valve Lifter The 2021 Escalade with the 6.2L L87 V8 is subject to a well-documented, widespread issue with failed Dynamic Fuel Management (DFM) valve lifters. GM has issued multiple Technical Service Bulletins, including #23-NA-043, and a service update (#N212353840) for broken valve lifter lock pin springs, which cause misfire codes P0300-P0308. This issue is so common it has led to class-action lawsuits and is frequently discussed in owner forums. Symptoms often include a distinct engine tick that precedes the check engine light.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.450 - 0.660 ohms. Failure: A reading significantly outside this range.
• Ignition Coil Secondary Resistance — expected: 6.1K - 8.22K ohms. Failure: A reading significantly outside this range.
• High Pressure Fuel System (Direct Injection) — expected: Ranges from ~435 PSI at startup to over 2,100 PSI under load.. Failure: Significantly lower pressure than specified, especially under load.
• Low Pressure Fuel System (Lift Pump) — expected: 51 - 87 PSI. Failure: Pressure dropping below 51 PSI.

Scan Tool Commands That Help

• GM GDS2: Cylinder Power Balance Test — To graphically display the power contribution of each cylinder in real-time. A significant drop or inconsistent reading for cylinder 8 helps confirm the misfire electronically, even if it's intermittent.
• GM GDS2: Fuel Injector Balance Test — To command the injector for cylinder 8 to flow for a specific duration and measure the corresponding pressure drop, comparing it against other cylinders to identify a clogged or failing injector.
• PicoScope (with knock sensor): Engine Bearing Defect Test (per recall N252494001) — This is a dealer-level procedure used to identify defective connecting rod bearings by analyzing engine vibrations at 2,000 RPM. While for a different recall, it demonstrates an advanced diagnostic capability for internal engine issues.

Wiring & Ground Locations

• G102 — Located at the left rear of the engine.. This is the primary ground for all 8 ignition coils. A poor connection here could cause weak spark or intermittent misfires on multiple cylinders, including cylinder 8.
• G103 — Located at the left rear of the engine compartment on the cowl, above the brake booster.. This is a main ground for the Engine Control Module (ECM). A faulty ground here can cause a wide range of erratic engine behavior and codes, including misfire detection errors.
• ECM Connector X3, Pins 48 & 68 — On the X3 connector at the Engine Control Module (ECM).. These are the specific control wires for the cylinder 8 fuel injector. Pin 48 is the low side and Pin 68 is the high side. They can be tested for resistance or shorts to rule out a wiring fault between the ECM and the injector.

Real Owner Repair Stories

• Chevy Trail Boss Forum user 'Pointman921' (2021 6.2L Trail Boss (L87 Engine), 10,310 miles) — Loss of power, check engine light, audible valve tick from passenger side bank, smoke from exhaust.
  ❌ Tried (didn't work) Initial dealer diagnosis suspected a broken valve spring.
  ✅ What actually fixed it The final diagnosis was a bent pushrod and a collapsed lifter on cylinder 4 (passenger side). The dealer replaced all lifters and guides on the passenger side bank (bank 2) per bulletin PIP5776.

OEM Part Supersession History

• AFM Lifter (e.g., HL-7011) → DFM Lifter (e.g., HL-7025, GM #12698946) — The newer DFM (Dynamic Fuel Management) lifter design was introduced for 2019+ L87 engines. This new lifter is backwards compatible with older AFM (Active Fuel Management) engines.
  Heads up: The newer DFM lifter (HL-7025) can be used in older AFM applications, but the original AFM lifter (HL-7011) CANNOT be used in a DFM engine like the 2021 L87.
• Unknown → Valve Spring (P/N 12691120) — A bad batch of valve springs was identified on engines built between June and October 2020.
  Heads up: For 6.2L L87 engines built in this timeframe, GM's bulletin instructed technicians to replace all valve springs on both banks, not just the failed one, indicating a potential quality issue with the entire set from that period.

Model Year Variations Within This Range

• 2021 models built between June 1, 2020 and October 7, 2020: These vehicles may have been built with a bad batch of valve springs, making a broken spring a more likely cause for a misfire compared to vehicles built outside this window. A specific GM service bulletin addresses this issue.