P0308 on 2018-2022 Cadillac Escalade: Cylinder 8 Misfire Causes and Fixes

What's Unique About the 2018-2022 Cadillac ESCALADE

The 6.2L V8 engines (L86 and L87) in this generation of Cadillac Escalade are equipped with Active or Dynamic Fuel Management (AFM/DFM). These systems are designed to improve fuel economy by deactivating cylinders, but they are a known weak point. The complex hydraulic lifters used in this system are prone to failure, where they can become stuck, collapse, or have their internal locking pins fail. This failure can lead to a misfire, a bent pushrod, and subsequent damage to the camshaft lobe, triggering code P0308. Numerous manufacturer Technical Service Bulletins (TSBs) have been issued that directly link misfire codes to these lifter, pushrod, and camshaft issues.

Diagnostic Flowchart

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

Generation note: This range covers two Escalade generations: the fourth (2018-2020) with the 6.2L L86 V8, and the fifth (2021-2022) with the 6.2L L87 V8. Both engines feature direct injection and advanced fuel management (AFM/DFM) and are highly susceptible to the valvetrain issues that can cause a P0308 code. The problem is widely reported across all GM trucks and SUVs using these engines.

Symptoms You May Notice

• Rough or shaking idle.
• Hesitation or stumbling during acceleration.
• Noticeable loss of engine power.
• Flashing or solid Check Engine Light.
• Reduced fuel economy.
• A distinct ticking or tapping noise from the engine, which strongly indicates a lifter, pushrod, or camshaft problem.
🎬 Watch: Hear what a failing L86 lifter sounds like

Most Likely Causes

1. Faulty Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a routine wear item. Carbon fouling, coolant contamination from a separate issue, or a cracked insulator can easily cause a misfire.
   How to confirm: Remove the spark plug from cylinder 8 (the rearmost cylinder on the passenger side) and inspect it for wear, damage, or heavy deposits. You can also swap it with a plug from another cylinder (e.g., cylinder 6) to see if the misfire code follows to P0306.
   Typical fix: Replace the spark plug. It is recommended to replace all 8 plugs at the same time for even performance. Use the specified gap, typically 0.040 inches for these engines.
   Est. part cost: $10-$25 per plug
2. Failed Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are reliable, but individual coils can fail from heat and vibration over time, leading to a weak or absent spark.
   How to confirm: Swap the ignition coil from cylinder 8 with one from an adjacent cylinder on the same bank (e.g., cylinder 6). Clear the codes and drive. If the code changes to P0306, the ignition coil is faulty.
   Typical fix: Replace the failed ignition coil.
   Est. part cost: $40-$90
3. Collapsed or Stuck Valve Lifter 🔴 High Probability This is a widespread and well-documented issue on GM's AFM/DFM V8s. TSBs #PIP5861, #23-NA-043, and #19-NA-219 all confirm that lifters can collapse, get stuck, or come apart, causing a misfire. The failure is often in the complex lifters used for cylinder deactivation.
   How to confirm: This requires advanced diagnosis. After ruling out ignition and fuel, listen for a distinct ticking/tapping noise. A mechanic will remove the valve cover to inspect the valvetrain for lack of movement at the rocker arm for cylinder 8. Confirmation often finds a collapsed lifter and a bent pushrod together.
   Typical fix: Requires replacing the failed lifter, the lifter guide, and often the camshaft if it has been damaged. TSB #PIP5861 recommends replacing all four lifters and the guide on the affected bank. Many owners opt to perform an 'AFM/DFM delete' at this time to prevent recurrence.
   Est. part cost: $500-$1,200 for parts (lifters, gaskets, bolts, camshaft)
4. Bent Pushrod 🔴 High Probability Often occurs as a direct result of a failed/collapsed lifter. TSB #23-NA-043 directly addresses misfires caused by bent pushrods. The force of the valvetrain acting on a stuck lifter can easily bend the pushrod, causing the valve to no longer open.
   How to confirm: After removing the valve cover for cylinder 8, the pushrod can be removed and inspected. It will often have a visible bend. A Reddit thread with a video shows a classic example on a '21 Escalade with a P0308 code.
   Typical fix: Replace the bent pushrod. However, the root cause (almost always a failed lifter) MUST be addressed. Simply replacing the pushrod without replacing the faulty lifter will result in another failure. The camshaft should also be inspected for damage.
   Est. part cost: $15-$40 for a single pushrod, but this is always part of a larger lifter repair job.
5. Loose or Damaged Spark Plug Wire 🟡 Medium Probability → Shop Spark Plug TSB #PIP5159C specifically notes that spark plug wires can become loose due to a missing 'C' clip on the wire end, leading to misfires. The connection can feel secure but may not have full electrical contact.
   How to confirm: Visually inspect and physically check the spark plug wire for cylinder 8. Ensure it is securely connected at both the ignition coil and the spark plug. A definitive 'click' should be felt.
   Typical fix: Reseat the wire securely or replace it if it's damaged or the clip is missing.
   Est. part cost: $15-$30 for a single wire
6. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector Direct injection injectors operate under high pressure and can become clogged or fail electronically. GM issued a special coverage program (N182202781) for injectors on some 2016-2017 models, indicating a known issue. A stuck-open injector can also wash out the cylinder, leading to damage.
   How to confirm: A mechanic can perform a fuel injector balance test with a scan tool. Swapping injectors is more labor-intensive than coils or plugs, so it's usually done after ruling out other causes. A forum user on Tahoe Yukon Forum confirmed a bad injector was their cause for P0308 after seeing raw fuel in the exhaust.
   Typical fix: Replace the faulty fuel injector. TSB 20-NA-098 warns to use the exact correct part number when replacing, as multiple versions exist.
   Est. part cost: $70-$150

Rare But Worth Checking

• Worn Camshaft Lobe: → Shop Engine Camshaft TSB #19-NA-219 mentions this as a possible cause alongside lifter issues. A failed lifter roller can quickly destroy the camshaft lobe, requiring both to be replaced. Diagnosis requires measuring valve lift or direct visual inspection.
🎬 Watch: Full teardown of a 6.2L engine with camshaft damage
• Broken Valve Spring: Also mentioned in TSB #19-NA-219 as a potential cause of a misfire and ticking noise. A broken spring may not be obvious and can sometimes pass a compression test, but will fail to control the valve at higher RPMs.
• Bad Ground for Ignition Coils: → Shop Ignition Coil A poor ground connection for the entire passenger-side bank of ignition coils (Bank 2) can cause multiple, intermittent misfires on that side, including on cylinder 8.
• Low Compression / Internal Engine Damage: Caused by more severe internal engine problems like a damaged piston, rings, or a leaking head gasket. A compression test and cylinder leak-down test will confirm this.

Diagnosis Steps

1. Read the code with an OBD-II scanner and confirm P0308 is present. Note any other codes like P0300 or P050D.
2. Check if the Check Engine Light is flashing. If so, minimize driving to prevent catalytic converter damage.
3. Locate cylinder 8. On the GM V8, cylinders are numbered 1-3-5-7 on the driver's side (front to back) and 2-4-6-8 on the passenger side. Cylinder 8 is the rearmost cylinder on the passenger side.
4. Inspect the spark plug wire for cylinder 8. Ensure it is clicked securely onto the coil and the spark plug, per TSB #PIP5159C.
5. Swap the ignition coil from cylinder 8 with the coil from cylinder 6. Clear the codes and run the engine. If the code changes to P0306, the coil is bad.
6. If the code remains P0308, move the spark plug from cylinder 8 to cylinder 6. If the code changes to P0306, the spark plug is bad.
7. If the code persists on cylinder 8, listen for a loud, consistent ticking noise from the passenger side valve cover area. This is a strong indicator of a mechanical valvetrain problem.
8. If a ticking noise is present, the next step is professional diagnosis involving removal of the valve cover to inspect the rocker arms, pushrods, and valve springs for cylinder 8. A bent pushrod or a rocker arm that is not moving are definitive signs of a lifter/cam issue.
9. If no obvious valvetrain issue is seen, perform a compression test and a cylinder leak-down test on cylinder 8 to check for internal engine health (rings, valves, head gasket).
10. If a lifter failure is confirmed, professional service is required for disassembly and repair. This involves replacing the failed lifter, the lifter guide, and often the camshaft if it has been damaged. TSB #PIP5861 recommends replacing all four lifters and the guide on the affected bank.

Parts You'll Likely Need

• Iridium Spark Plug (OEM #41-162) — This is the most common wear item that causes a single-cylinder misfire. It's the first and cheapest part to check.
  Trusted brands: ACDelco, NGK
  OEM price range: $15-$25
  Aftermarket price range: $10-$20
• Ignition Coil (OEM #12674754) — A common failure point that is easily diagnosed by swapping its position.
  Trusted brands: ACDelco, Delphi
  OEM price range: $60-$90
  Aftermarket price range: $35-$60
• Valve Lifter (AFM/DFM) (OEM #12698945) — The primary culprit in the majority of serious P0308 cases on this platform. A known major failure point documented by multiple TSBs.
  Trusted brands: ACDelco, General Motors
  OEM price range: $30-$50 per lifter
  Aftermarket price range: $20-$40 per lifter
• Valve Lifter Guide (OEM #12681273 or 12669185) — Always replaced when replacing lifters, as recommended by GM TSBs like PIP5861. They prevent the lifters from rotating in their bores.
  Trusted brands: ACDelco, General Motors
  OEM price range: $20-$30
  Aftermarket price range: $10-$20
• Camshaft (OEM #12689035) — Often required if a failed lifter's roller has damaged the corresponding lobe on the camshaft. TSB 19-NA-219 notes this possibility. Inspection is mandatory during a lifter replacement job.
  Trusted brands: General Motors
  OEM price range: $250-$400
  Aftermarket price range: $200-$350

Related Codes That Often Appear With This One

• P0300 — This code for 'Random Misfire' often appears with a specific cylinder misfire code like P0308, especially in the early stages of a component failure or if the issue is intermittent. All cited TSBs for lifter issues list P0300 along with the specific cylinder codes.
• P050D — This code for 'Cold Start Rough Idle' is frequently associated with valvetrain issues like sticking lifters, as noted in TSB #PIP5628G.

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-043: Addresses misfires (P0300-P0308) caused by bent pushrods and collapsed lifters, providing replacement guidelines based on vehicle mileage.
• 19-NA-219: Supersedes PIP4138R. Provides diagnostic tips for misfires and engine noises, identifying worn cam lobes, sticking valves, broken valve springs, and collapsed AFM lifters as potential causes.
• PIP5861: Preliminary information about misfires (P0300-P0308) where a lifter has come apart. Recommends replacing the lifter guide and all four lifters on the affected bank.
• PIP5628G: Information for diagnosing misfire DTCs P0300-P0308 and/or P050D (Cold Start Rough Idle).
• PIP5159C: Notes that a loose spark plug wire, potentially from a missing 'C' clip, can cause misfire codes P0300-P0308.
• 20-NA-098: Warns technicians to use the correct part number when replacing fuel injectors to avoid fuel trim issues and misfires.

Platform-Specific Known Issues

• AFM/DFM Lifter Failure: The most significant issue for this platform. The lifters used for cylinder deactivation can become stuck or collapse, preventing the valve from opening correctly and causing a misfire. TSB #PIP5861 recommends replacing the lifter, guide, and all four lifters on the affected bank if one fails. [Bulletin #PIP5861, 1, 29]
• Worn Camshaft Lobes: Often a direct result of a failed lifter. The roller on the lifter can seize and grind down the corresponding lobe on the camshaft, requiring camshaft replacement. [Bulletin #PIP4138R, 27]
• Loose Spark Plug Wires: TSB #PIP5159C points out that a missing 'C' clip on the spark plug wire can cause a loose connection and intermittent misfires.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: ~0.450 - 0.660 ohms. Failure: A reading significantly outside this range indicates a faulty coil winding.
• Ignition Coil Secondary Resistance — expected: ~6.1K - 8.22K ohms. Failure: A reading significantly outside this range suggests a failure in the secondary coil windings.
• High Pressure Fuel System (Direct Injection) — expected: Over 2,100 PSI (150 bar / 15 MPa). Can range from ~4352 PSI at startup to over 20,000 PSI under load.. Failure: Pressure that is significantly below commanded pressure on a scan tool indicates a problem with the high-pressure fuel pump or sensor.
• Low Pressure Fuel System (Lift Pump) — expected: ~51-87 PSI (3.5-6.0 bar). Failure: Low pressure from the in-tank pump will starve the high-pressure pump, causing misfires and other codes.

Scan Tool Commands That Help

• GDS2 (or other professional scan tool): Cylinder Power Balance Test — This is a primary diagnostic step after checking for spark and codes. The test disables one fuel injector at a time and measures the corresponding drop in engine RPM. A cylinder that shows little or no RPM drop when disabled is not contributing power, confirming the misfire location without swapping parts. It is preferred over disabling the ignition coil to avoid sending raw fuel to the catalytic converter.
• GDS2 (or other professional scan tool): AFM/DFM System Tests — To check the functionality of the cylinder deactivation system. A technician can command the system on and off to monitor the response of solenoids and lifters, which can help diagnose a stuck or malfunctioning component related to the valvetrain.

Wiring & Ground Locations

• G102 — Located at the left rear of the engine block/cylinder head.. This is a primary ground point for all 8 ignition coils. A loose or corroded connection here can cause weak spark and intermittent misfires on any cylinder, including cylinder 8.
• G103 / G104 — Located on the rear of the cylinder heads (one on each side). G103 is typically on the passenger (right) side, G104 on the driver (left) side.. These are major engine grounds. A poor connection on G103 (passenger side) could affect sensors and actuators on Bank 2 (which includes cylinder 8), leading to erratic behavior and misfires.
• Engine Control Module (ECM) Connector — Typically mounted on the driver's side of the engine bay.. All signals for the ignition coil and fuel injector for cylinder 8 originate here. A visual inspection for corrosion or pushed-out pins at the main harness connector is a valid diagnostic step if direct testing of the components shows no faults.

Real Owner Repair Stories

• Reddit user in r/gmcsierra (2020 GMC with 6.2L engine, 84,000 miles) — Check engine light with code P0308.
  ❌ Tried (didn't work) The user did not specify preliminary steps, but the diagnosis quickly pointed to an internal issue.
  ✅ What actually fixed it The #8 lifter failed and subsequently damaged the camshaft. The repair involved replacing the lifters and the camshaft. The repair was covered by an extended warranty.

OEM Part Supersession History

• Various, including 12571595, 12619820, 12639516 (AFM Lifters) → GM 12698946 (Elgin HL-7025) — The newer DFM (Dynamic Fuel Management) lifter was introduced and is backward-compatible with older AFM (Active Fuel Management) applications.
  Heads up: The new DFM lifter (12698946) WILL work in older AFM engines, but the original AFM-only lifters will NOT work in the newer DFM engines.
• N/A (AFM/DFM Camshaft) → GM 12689035 — This is not a supersession, but the standard non-AFM/DFM camshaft used in factory engines and is the go-to part for owners performing an 'AFM/DFM delete' to prevent lifter failure.
  Heads up: Using this camshaft requires reprogramming the ECM to disable the AFM/DFM system to prevent severe engine running issues.
• 12576400, 12648846 (Standard Lifter) → GM 12698945 — Updated part for the standard (non-deactivating) hydraulic roller lifter.

Model Year Variations Within This Range

• 2018-2020 (L86 Engine): These model years use the 6.2L L86 V8 with Active Fuel Management (AFM). AFM deactivates a fixed set of four cylinders (1, 4, 6, and 7) to save fuel. Therefore, a P0308 misfire on an L86 engine is NOT caused by a failure of a special deactivating lifter, but rather a standard lifter or other common causes (spark, fuel, coil).
• 2021-2022 (L87 Engine): These model years use the 6.2L L87 V8 with Dynamic Fuel Management (DFM). DFM is more advanced and can deactivate any of the 8 cylinders individually. This means that on an L87, a P0308 misfire CAN be caused by the failure of a DFM deactivating lifter, in addition to all other common causes.