P0308 on 2019-2025 Chevy Silverado: Cylinder 8 Misfire Causes & Fixes

What's Unique About the 2019-2025 Chevrolet Silverado 1500

The 5.3L L84 and 6.2L L87 V8 engines in this generation of Silverado use Dynamic Fuel Management (DFM), an advanced version of Active Fuel Management (AFM), to improve fuel economy by deactivating cylinders. Unlike the older AFM system that deactivated a fixed set of cylinders, DFM can deactivate any combination of cylinders, meaning all 16 lifters are the complex, failure-prone type. These specialized hydraulic lifters are a well-documented, widespread failure point, often collapsing or having their internal locking pin break. These lifter failures are a primary cause of misfire codes, including P0308, and are the subject of multiple Technical Service Bulletins (TSBs) and class-action lawsuits from GM.

Symptoms You May Notice

• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Reduced engine power and entering 'limp mode'
• Flashing or solid Check Engine Light
• Engine noise (ticking, chirping, or knocking) that may be more pronounced on startup or off-idle
• Service StabiliTrak warning light may appear with the check engine light

Most Likely Causes

1. Failed DFM/AFM Lifter or Valvetrain Component 🔴 High Probability → Shop Engine Valve Lifter The L84 and L87 engines use a complex Dynamic Fuel Management (DFM) system. The specialized lifters for this system are a known, widespread failure point, often collapsing or having their roller get stuck. This issue is so common it has prompted multiple GM Technical Service Bulletins (TSBs) and class-action lawsuits. Failures have been reported at very low mileage, sometimes under 10,000 miles.
   How to confirm: After ruling out ignition/fuel issues, a distinct ticking/tapping noise from the upper engine is a strong indicator. 🎬 Watch: How to diagnose lifter tick vs other engine noises. A technician will confirm by removing the valve cover for cylinder 8 to observe the rocker arm for lack of movement while cranking the engine. A compression test may show low compression, and a cylinder leak-down test can help pinpoint a valve sealing issue, which is often a consequence of the lifter failure.
   Typical fix: Replace all 16 lifters, lifter guides, and often the camshaft, which gets damaged by the failed lifter. This is a labor-intensive repair requiring removal of the cylinder heads, intake manifold, and front engine cover. 🎬 See this full repair guide for replacing collapsed lifters. Due to the high failure rate, many owners opt for an aftermarket 'AFM/DFM Delete Kit' which replaces the complex lifters with standard ones and requires an ECU tune to disable the system.
   Est. part cost: $500-$1800
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 on the same passenger side bank). Clear the codes and run the engine. If the misfire code changes to P0306, the ignition coil is faulty. This is a very common and simple diagnostic step.
   Typical fix: Replace the faulty ignition coil. This is a simple repair, as the coil is located directly on top of the valve cover, held by a single bolt.
   Est. part cost: $40-$100
3. Worn or Fouled Spark Plug / Faulty Wire 🟡 Medium Probability → Shop Spark Plug
   How to confirm: Remove the spark plug from cylinder 8 and inspect it for wear, oil/carbon fouling, or damage to the porcelain insulator. Inspect the spark plug wire for damage, corrosion, or a loose connection. TSB PIP5159C specifically notes a loose wire can cause misfires.
   Typical fix: Replace the spark plug and/or wire. If plugs are near their 100,000-mile service interval, it is best practice to replace all 8.
   Est. part cost: $10-$25 for a single plug/wire, $80-$200 for a full set.
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector
   How to confirm: After ruling out ignition issues, a technician can test the injector's function using a specialized scan tool (like the AFIT tool mentioned in TSB PIP5628G) or by checking its resistance. Leaking injectors on these engines are a known issue that can cause various misfires and rough running.
   Typical fix: Replace the clogged or failed fuel injector.
   Est. part cost: $70-$150

Rare But Worth Checking

• Coolant Leak onto Spark Plug Wire: → Shop Spark Plug A known issue on GM trucks involves a leak from the heater core quick-connect hoses on the firewall. These hoses are located directly above the cylinder 8 position, and dripping coolant can short out the spark plug wire, causing a P0308. A user on GM-Trucks.com reported this exact scenario resolving their P0308.
🎬 Watch: How to find and fix this common heater hose leak.
• Bent Pushrod or Broken Valve Spring: These are often secondary damage resulting from a collapsed lifter. TSB 19-NA-219 mentions these as possible causes for misfire codes accompanied by engine noise. A Reddit user's video of a failed L84 lifter also showed a bent exhaust pushrod as a result.

Diagnosis Steps

1. Check for other stored diagnostic trouble codes (DTCs) that could provide more clues.
2. Perform a visual inspection of the cylinder 8 area (rear passenger side). Look for loose electrical connectors, damaged wiring, or signs of coolant leaks from the heater hoses on the firewall above.
3. Swap the ignition coil from cylinder 8 with another cylinder (e.g., cylinder 6). Clear the codes and see if the misfire moves to the new cylinder (P0306). If it does, the coil is bad.
4. If the misfire remains on cylinder 8, swap the spark plug with another cylinder. If the misfire moves, the plug is bad. Inspect the old plug for signs of oil, fuel, or coolant fouling.
5. If ignition components are good, listen for a distinct ticking or tapping sound from the engine, which strongly suggests a valvetrain problem like a failed lifter.
6. If a mechanical issue is suspected, perform a cylinder compression test and a cylinder leak-down test to assess the mechanical health of cylinder 8.
7. If compression is low or leak-down test indicates a valve issue, remove the valve cover to visually inspect the valve springs, pushrods, and rocker arms for proper movement while the engine is manually cranked. A rocker arm that isn't moving indicates a collapsed lifter.

Parts You'll Likely Need

• Engine Valve Lifter Kit (DFM) (OEM #12698945) — This is the most probable serious failure causing a P0308 code on these engines due to the high failure rate of DFM lifters. A complete kit including all 16 lifters, guides, head gaskets, and head bolts is required for the repair.
  Trusted brands: ACDelco, General Motors
  OEM price range: $400-$800
  Aftermarket price range: $250-$500
• Ignition Coil (OEM #12619161) — An ignition coil provides the high voltage to the spark plug. They are a common failure point and a primary cause of single-cylinder misfires.
  Trusted brands: ACDelco, NGK, Delphi
  OEM price range: $70-$120
  Aftermarket price range: $40-$80
• Spark Plug (OEM #12622441 (ACDelco Iridium)) — Spark plugs are a standard maintenance item that wear out over time. A fouled or worn plug is a simple and common cause for a misfire.
  Trusted brands: ACDelco, NGK
  OEM price range: $15-$25
  Aftermarket price range: $8-$15

Related Codes That Often Appear With This One

• P0300 — If the lifter issue is severe or other problems are present (like widespread fuel injector issues), the misfire may become random or affect multiple cylinders, triggering a P0300 (Random/Multiple Cylinder Misfire) code.
• P050D — This code for "Cold Start Rough Idle" is often seen alongside misfire codes when the root cause is related to valvetrain or fuel injector issues, as noted in TSB PIP5628G.

Technical Service Bulletins (TSBs) & Recalls

• 19-NA-219: Diagnostic aid for engine

Platform-Specific Known Issues

• Widespread DFM/AFM Lifter Failure: The most significant issue for the L84/L87 engines. Failures are common and can occur at low mileage, leading to misfire codes and costly engine repairs.
• Coolant Leak from Heater Hose Connectors: The plastic connectors on the firewall can degrade and leak coolant directly onto the cylinder 8 ignition components, causing a misfire.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.4 to 2 ohms. Failure: A reading of 0 ohms (short) or infinite/OL (open circuit) indicates a failed coil.
• Ignition Coil Secondary Resistance — expected: 6,000 to 10,000 ohms. Failure: A reading significantly outside this range, or OL (open circuit), indicates a failed coil.
• Fuel Injector Coil Resistance (Direct Injection) — expected: Approximately 12-15 ohms. Failure: A reading significantly outside this range suggests a faulty injector coil.
• Low-Pressure Fuel System (Key On, Engine Off) — expected: 55 to 62 PSI. Failure: Pressure below 55 PSI can indicate a weak in-tank fuel pump or clogged filter, starving the high-pressure pump.
• Engine Compression — expected: 120 to 150 PSI per cylinder. Failure: A reading below 120 PSI, or a variation of more than 15-20% between cylinders, points to mechanical engine damage such as worn piston rings or a poor valve seal, often a consequence of lifter failure.

Hidden / Shadow Codes Worth Checking

• Misfire History Counter (Per Cylinder): This is not a DTC but a live data parameter (PID) that shows the number of misfire events counted for each specific cylinder over a drive cycle. A high count on cylinder 8, even if a P0308 has not yet set, can confirm an intermittent issue before it becomes a constant fault. (see via Requires a professional-grade scan tool like the GM GDS2 or an advanced aftermarket scanner with access to GM-specific PIDs.)

Scan Tool Commands That Help

• GM GDS2 (or equivalent): Cylinder Power Balance Test — This active test helps confirm a P0308. The tool disables each cylinder one by one and measures the RPM drop. A smaller RPM drop for cylinder 8 confirms it is contributing less power than the others.
• GM GDS2 (or equivalent): Fuel Injector Balance Test — This test fires each injector for a set duration and measures the corresponding fuel pressure drop. If the pressure drop for cylinder 8 is significantly different from the others, it points to a clogged or failing injector. This is a definitive test before replacing the part.

Wiring & Ground Locations

• ECM Connector X1, Pin 66 (L84) — At the Engine Control Module (ECM).. This specific pin is the Ignition Control (IC) signal for the cylinder 8 ignition coil. A wiring issue (short/open) on this circuit (typically a Dark Blue wire) between the ECM and the coil will cause a P0308.
• ECM Connector X3, Pin 42 (L83 - older but relevant) — At the Engine Control Module (ECM).. On some engine variants, this pin (typically a Dark Green/White wire) serves as the control for the cylinder 8 fuel injector. A fault in this circuit can cause the injector to stop firing, leading to a misfire.
• G110 / G114 — These are key engine and body ground points. Their exact location can vary but are typically found on the engine block, cylinder heads, or frame rails near the front of the engine bay.. A loose or corroded main engine ground can cause numerous electrical issues, including weak spark or erratic sensor readings that can lead to misfire codes. While not specific to cylinder 8, it's a foundational check for any electrical diagnosis.

Real Owner Repair Stories

• Forum user on ChevyTrucks.org, cited in Go-Parts article (GMT800/900 Truck (Slightly older but same root cause)) — Persistent P0308 code.
  ❌ Tried (didn't work) Standard diagnostics (plugs, coils, wires)
  ✅ What actually fixed it The owner discovered a coolant leak from a heater core quick-connect fitting on the firewall. The coolant was dripping directly onto the cylinder 8 spark plug wire, causing it to short out. Replacing the leaking fitting and the damaged wire resolved the code.
• GM-Trucks.com forum user (2025 Silverado 1500 5.3L L84 with 2,800 miles) — Engine knocking noise, dealer acknowledged issue.
  ✅ What actually fixed it Vehicle was diagnosed with failed lifters, requiring replacement under warranty. This story highlights that the DFM lifter issue persists even on the latest model years and at extremely low mileage.
• Forum user on various GM truck forums (Various GM trucks/SUVs with 5.3L V8) — Persistent P0308 after replacing plug and coil.
  ❌ Tried (didn't work) Spark plug replacement, Ignition coil replacement
  ✅ What actually fixed it A leaking valve cover gasket allowed engine oil to pool in the spark plug well for cylinder 8. This saturated the spark plug boot and fouled the plug. Replacing the valve cover gasket and cleaning the oil out of the well was the final fix.

OEM Part Supersession History

• 12648846, 12576400 → 12698945 — This is the service part number for the DFM/AFM valve lifter. While GM does not officially state the reason for supersession, it is common for part numbers to be updated to reflect design revisions or supplier changes aimed at improving reliability.
  Heads up: Despite part number changes, forum users report that the fundamental design and failure mode remain similar across revisions. A user on GM-Trucks.com noted that the same service part number (12698945) is used for repairs on models from 2006 to 2026, indicating a lack of a fundamental redesign in the service part.

Model Year Variations Within This Range

• 2021-2022: Due to the global microchip shortage, some 2021 and 2022 Silverado/Sierra 1500 models equipped with the 5.3L L84 V8 were built without the Dynamic Fuel Management (DFM) system. These trucks received a credit on the window sticker and are not susceptible to DFM-related lifter failures. However, the majority of trucks still included the system.
• 2022.5+: The 2022 model year had a mid-cycle refresh (often called 2022.5). While the L84/L87 engines were carried over, there were significant changes to the truck's interior and electronics. However, the DFM system and its potential for lifter failure remained unchanged from a mechanical standpoint.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• 8-Speed & 10-Speed Transmission Issues (Shudder/Hard Shifting) 🔴 High — Widespread on 2019+ models. The 8-speed is known for shuddering, while the 10-speed has had recalls for valve body issues that can cause harsh shifts or even wheel lock-up. (Ref: Multiple TSBs and recalls exist, including NHTSA Campaign Number 24V-433 for the 10-speed transmission control module software.)
• DFM/AFM Lifter Failure 🔴 High → Shop Engine Valve Lifter — Very common across all 2019+ V8 models. Failures can occur at any mileage, but a notable number of failures happen early, under 50,000 miles. (Ref: TSB 19-NA-219, 21-NA-173, and others address diagnosis. Subject of multiple class-action lawsuits.)
• Infotainment System Glitches 🟠 Medium — Commonly reported across 2019-2024 models. Issues include black/unresponsive screens, Bluetooth connectivity problems, and random volume spikes. (Ref: Software updates have been released to address some, but not all, of the reported problems.)
• Power Sliding Rear Window Leaks 🟠 Medium — Frequently reported on 2019-2023 models equipped with this option. Leaks occur around the window frame, leading to water stains on the headliner and potential mold. (Ref: GM has issued service bulletins to address the seal design.)
• 6.2L L87 Engine Bearing Failure 🔴 High — Affects a subset of 2021-2024 models with the 6.2L L87 engine, leading to sudden engine seizure. Less common than lifter failure but catastrophic when it occurs. (Ref: Subject of NHTSA investigation and GM Safety Recall N232413400.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this specific P0308 repair, used parts are generally not recommended for core components. A used ignition coil or a wiring harness pigtail from a low-mileage donor vehicle could be a cost-effective choice for diagnosis or a quick fix. Avoid all used internal engine components.

Donor-vehicle mileage cap: roughly under 50000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For an ignition coil, check for cracks in the housing or corrosion on the connector pins.
• For a wiring pigtail, ensure the plastic connector is not brittle and the locking tab is intact. Check for at least 6 inches of clean, undamaged wire.
• Verify the donor vehicle was not involved in a front-end collision or engine fire.

OEM-only on this vehicle (don't cheap out):

• Engine Valve Lifters: NEVER use used DFM lifters. The failure rate is extremely high even on new parts; installing used ones is guaranteeing a repeat failure. Always buy new OEM (ACDelco/GM) or a reputable full AFM/DFM delete kit.
• Head Gaskets & Head Bolts: These are one-time-use parts and must be purchased new for a lifter repair job.

Aftermarket brands forum-validated for this vehicle:

• Range Technology / Pulsar: For OBD-II plug-in AFM/DFM Disablers, which can help prevent lifter failure by keeping the engine in V8 mode.
• Texas Speed & Performance: For full mechanical AFM/DFM Delete Kits that replace the camshaft and lifters.
• NGK / ACDelco: For spark plugs and ignition coils, these are trusted OEM-quality brands.

Brands owners have reported issues with on this vehicle:

• No-name or unbranded DFM lifter kits from online marketplaces. The quality control on these critical components is often poor, leading to premature and catastrophic failure. Stick to OEM or well-known performance brands for internal engine parts.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0300 — Random or multiple cylinder misfire code; often accompanies P0308 if the DFM failure affects multiple cylinders or if the fuel/ignition issue is not isolated.
• P0306 — Cylinder 6 misfire; used during the diagnostic 'swap test' where the cylinder 8 coil is moved to cylinder 6 to see if the misfire follows the part.
• PIP5159C — While not a DTC, this TSB is frequently associated with P0308 as it identifies loose spark plug wires as a primary cause for misfires on this engine family.
• PIP5628G — A technical service bulletin related to diagnosing fuel injector failures which can cause the P0308 code.

Frequently Asked Questions