P0308 on 2011-2018 Ram 1500 5.7L HEMI: Cylinder 8 Misfire Causes and Fixes

What's Unique About the 2011-2018 Ram 1500

For the 2011-2018 Ram 1500 with the 5.7L HEMI, a P0308 code must be taken very seriously. While it can be caused by simple ignition parts, it is also a well-documented symptom of a deeper mechanical problem specific to this engine: camshaft and lifter failure. The lifters, particularly those associated with the Multi-Displacement System (MDS), can fail due to wear or lubrication issues. This causes the roller on the lifter to seize, stop spinning, and grind down the camshaft lobe. This results in a permanent misfire that won't be fixed by replacing ignition or fuel parts. A video from a user with a high-mileage Ram shows a rocker arm that has completely fallen off due to a failed lifter on cylinder 8, directly causing a P0308 code.

Symptoms You May Notice

• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Solid or flashing Check Engine Light
• Fuel smell from the exhaust
• Audible ticking noise from the engine, often called the 'Hemi Tick'

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Coil-on-plug systems are common failure points due to heat and vibration. It's the easiest component to test and a frequent cause of single-cylinder misfires.
   How to confirm: Swap the ignition coil from cylinder 8 with another cylinder (e.g., cylinder 6, which is next to it on the passenger side bank). Clear the codes and drive. If the code changes to P0306, the coil is faulty.
   Typical fix: Replace the faulty ignition coil. Consider replacing all 8 if they are original and the vehicle has high mileage.
   Est. part cost: $30-$75
2. Worn or Fouled Spark Plugs 🔴 High Probability The 5.7L HEMI uses two spark plugs per cylinder (16 total), increasing the chances of a failure. They are a regular maintenance item and can wear out, causing a weak spark. Oil leaking from a valve cover gasket can also foul the plugs in the spark plug tubes.
   How to confirm: After ruling out the coil, remove the two spark plugs from cylinder 8. Inspect them for wear (worn electrode), carbon buildup, or oil fouling. Compare them to plugs from a working cylinder. The recommended gap is 0.044 inches.
   Typical fix: Replace the spark plugs. It is recommended to replace all 16 plugs at the same time for consistent performance using OEM-spec plugs. Torque new plugs to 13 ft-lbs.
   Est. part cost: $50-$150 for a full set of 16
3. Failed Camshaft and/or Lifter(s) 🟡 Medium Probability This is a widely known issue on 5.7L HEMI engines, often called 'Hemi Tick'. The MDS lifters can fail, leading to the destruction of the camshaft lobe for that cylinder. This can happen even on well-maintained trucks, and cylinder 8 is a common point of failure.
   How to confirm: If swapping the coil and plugs does not resolve the P0308 code, this is the next logical suspect. A persistent ticking noise from the engine is a strong indicator. A compression test will likely show low compression on cylinder 8. Definitive confirmation requires removing the passenger side valve cover to inspect the rocker arms and valve springs. A dislodged rocker arm is a clear sign of a collapsed lifter and subsequent cam lobe damage.
   Typical fix: This is a major engine repair requiring replacement of the camshaft, all 16 lifters, head gaskets, and other related components. Many owners and shops opt to install a non-MDS camshaft and lifter kit to prevent recurrence, which requires disabling the MDS system in the PCM 🎬 Watch: A walkthrough of the camshaft and lifter replacement process. via a tuner.
   Est. part cost: $800-$2000 for parts alone.
4. Faulty Fuel Injector ⚪ Low Probability
   How to confirm: If ignition components are good, you can swap the fuel injector from cylinder 8 with another cylinder. This is more involved than swapping a coil. If the misfire code follows the injector, the injector is the problem. You can also test the injector's resistance, which should be around 10 - 18 Ohms. A 2020 model showed a reading of 11.5 Ohms.
   Typical fix: Replace the faulty fuel injector.
   Est. part cost: $50-$120

Rare But Worth Checking

• Leaking Valve Cover Gasket: The spark plug tubes can fill with oil from a leaking valve cover gasket, which can short out the ignition coil and foul the spark plugs, causing a misfire. This should be checked when inspecting the spark plugs.
• Broken Exhaust Manifold Bolts: The exhaust manifold bolts on HEMI engines are known to break due to heat cycles, causing an exhaust leak. The resulting ticking sound can sometimes be confused with the 'Hemi Tick' of a failing lifter. An exhaust leak near the cylinder 8 oxygen sensor could potentially affect its readings and contribute to a misfire code, though this is less common.
• PCM Software Issue: While less common for this specific generation, some Chrysler TSBs for similar platforms address misfire codes being falsely triggered by overly sensitive PCM logic. TSB 18-022-21 for the 2020 Ram mentions a software update to fix P0300-P0308 codes. It's worth checking if any updates are available for your specific VIN. Manufacturer TSB Bulletin #18-093-15 notes that P0300 through P0308 misfires can occur when the vehicle is started cold and the driver immediately places the vehicle in drive.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0308.
2. Check for a flashing Check Engine Light. If flashing, avoid driving to prevent catalytic converter damage.
3. Listen for a distinct ticking sound from the passenger side of the engine, which could indicate lifter/cam failure.
4. Locate cylinder 8 (passenger side, rearmost cylinder, near the firewall).
5. Swap the ignition coil from cylinder 8 with the coil from cylinder 6 (the one in front of it). Clear codes and test drive. If the code changes to P0306, replace the ignition coil.
6. If the code remains P0308, inspect the spark plug tube for oil (indicating a valve cover gasket leak). Then, remove and inspect the two spark plugs in cylinder 8 for wear, damage, or fouling. If they are worn, replace them. It's best practice to replace all 16.
7. If the code persists, the problem is likely not a simple ignition issue. A Reddit user with a 2011 Ram 1500 reported swapping plugs, coil, and injector with no success, pointing towards a deeper mechanical or wiring issue.
8. Perform a compression test on cylinder 8. A reading significantly lower than other cylinders points to a mechanical problem.
9. If compression is low, the next step is to remove the valve cover for a visual inspection of the valvetrain (rocker arms, springs). A dislodged rocker arm is a definitive sign of a collapsed lifter and damaged camshaft.
10. If all else fails, consider a potential wiring issue to the coil or injector, or a rare PCM fault. Rodent damage to wiring harnesses has been reported as a final cause after all other parts were checked.

Parts You'll Likely Need

• Ignition Coil (OEM #56029129AF) — This is one of the most common failure items for a single-cylinder misfire and is the first part to check.
  Trusted brands: Mopar, NGK, Denso
  OEM price range: $45-$70
  Aftermarket price range: $30-$55
• Spark Plugs (Set of 16) (OEM #SP143877AB (for 2014+ models, supersedes older numbers)) — Worn spark plugs are a common cause of misfires. The 5.7L HEMI has two per cylinder. The OEM Mopar plug is often a re-branded NGK Iridium plug.
  Trusted brands: NGK (LZFR5C-11 or 92145 Laser Iridium), Champion
  OEM price range: $100-$180
  Aftermarket price range: $50-$120
• Camshaft and Lifter Kit (Non-MDS Conversion) — For a persistent P0308 not caused by ignition or fuel parts, this is the likely mechanical failure point specific to the 5.7L HEMI. Converting to non-MDS lifters is a common, more durable repair.
  Trusted brands: Mopar (using non-MDS components, e.g., P/N 5038784AD), Texas Speed & Performance, Melling
  OEM price range: $1200-$2000
  Aftermarket price range: $800-$1500

Related Codes That Often Appear With This One

• P0300 — If the misfire is severe or affects multiple cylinders, a P0300 (Random/Multiple Cylinder Misfire) may be stored alongside P0308.
• P2099 — A rich condition on bank 2 (P2099) can sometimes be seen with misfires on that bank, including P0308, as reported by a forum user.

Technical Service Bulletins (TSBs) & Recalls

• TSB #18-022-21: While for a newer model year (2020), this TSB shows that Chrysler has addressed P0300-P0308 misfire codes via PCM software updates, indicating a history of software sensitivity.
• TSB #09-002-14 REV. B: Although for the 3.6L Pentastar, this TSB highlights Chrysler's methodology for diagnosing internal engine misfires (leak-down tests), which is relevant for confirming a mechanical P0308 on a HEMI.
• TSB Bulletin #1800624: This bulletin involves reprogramming the PCM with the latest software to address engine misfires, including P0308.
• TSB Bulletin #1814522: Notes that customers may experience an engine misfire and provides guidance for P0308 and other cylinder-specific codes.
• TSB Bulletin #18-093-15: Identifies that P0300 through P0308 misfire conditions can occur during cold starts followed by immediate engagement of the transmission.

Platform-Specific Known Issues

• Camshaft/Lifter Failure: The most significant issue for this platform. A P0308 code that persists after basic ignition and fuel component swaps is highly suspect for this mechanical failure. The failure is often attributed to the MDS (Multi-Displacement System) lifters, whose roller bearings can seize and destroy the camshaft lobe.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.558 - 0.682 Ohms at 70-80°F. Failure: A reading outside this range indicates a faulty coil winding.
• Fuel Injector Resistance — expected: 10 - 18 Ohms. Failure: A reading significantly higher or lower than other injectors, or an open/zero reading, indicates a bad injector. A 2020 model showed 11.5 Ohms as a good reading.
• Fuel Pressure (at fuel rail) — expected: 58 psi +/- 5 psi. Failure: Significantly lower pressure points to a failing fuel pump or regulator.
• Cylinder 8 Coil Connector Voltage (Key On, Engine Off) — expected: One wire should have battery voltage (approx. 12V).. Failure: No voltage on the power feed wire points to an issue with the ASD relay or its circuit.

Hidden / Shadow Codes Worth Checking

• Mode 6, Test ID $82, Comp ID $08: This is not a formal code, but a diagnostic data monitor for misfire counts on cylinder 8. It allows a technician to see raw misfire data, even if the count is not yet high enough to trigger a P0308 trouble code. (see via An advanced OBD-II scan tool capable of displaying Mode 6 data.)

Scan Tool Commands That Help

• wiTECH or high-end aftermarket scanner: Injector Balance Test / Cylinder Contribution Test — This function deactivates injectors one by one and monitors the corresponding drop in engine RPM. If deactivating the cylinder 8 injector causes no change in RPM, it confirms that cylinder was not contributing power in the first place, helping to isolate the fault.

Wiring & Ground Locations

• Engine Ground Strap — A ground strap is located at the rear of the driver's side cylinder head, attaching to the firewall.. A poor or broken engine ground can cause a wide range of electrical issues, including erratic behavior from ignition and fuel components that could lead to a misfire.
• Main Chassis Ground — A common ground point is located on the driver's side wheel well, forward of the upper control arm.. This is a primary ground for multiple engine components. A loose or corroded connection here could cause issues for components on the passenger side bank where cylinder 8 is located.
• Engine Harness Chafe Points — Visually inspect the main wiring harness where it may rub against the shock tower, upper control arm, or engine brackets. The harness leading to the rearmost cylinders is also susceptible to heat damage from the exhaust manifold.. Vibration and heat can cause wires to chafe or melt, creating a short or open circuit for the cylinder 8 ignition coil or fuel injector, leading to a persistent misfire.

Real Owner Repair Stories

• YouTube user 'Sean's DIY & Reviews' (2006 Ram 1500 5.7L with 245,000 miles (Note: older generation but identical P0308 cause)) — P0308 code, check engine light, audible engine tick.
  ❌ Tried (didn't work) Replacing the spark plug on cylinder 8, Swapping ignition coils between cylinders
  ✅ What actually fixed it Upon removing the valve cover, the rocker arm for cylinder 8 had completely fallen off and was lying in the head. This was caused by a failed lifter, which prevented the valve from opening and created the misfire. The fix required replacing the lifters and reinstalling the valvetrain.
• Reddit user 'coffeedrinker2018' and commenter 'BinkyBass' (2011 Dodge Ram 1500 5.7L with 357,000 km) — Rough running, P0308 code.
  ❌ Tried (didn't work) New spark plugs, Swapping the coil pack with cylinder 6, New fuel injector on cylinder 8
  ✅ What actually fixed it The original poster did not provide the final fix, but another user commented that they had identical symptoms that were ultimately resolved by finding an injector wire that had been chewed by a rodent. The damage was subtle and only found after a very close inspection of the wiring harness.
• RamForum.com user (2015 Ram 1500 5.7L with 98k miles) — Intermittent P0308 code, sometimes causing the engine to shut off after remote start.
  ❌ Tried (didn't work) Replacing all spark plugs, Swapping coils between cylinders 7 and 8
  ✅ What actually fixed it Another user with a similar multi-year intermittent misfire issue reported that the final solution was three consecutive treatments with Red Line SI-1 fuel system cleaner, which restored fuel mileage and eliminated the misfire code.

"I Checked Everything" — The Actual Cause

• In a case where ignition parts (plugs, coil) and fuel parts (injector) were all replaced without fixing the P0308, the root cause was found to be a rodent-chewed wire in the injector harness. This type of fault would not be found by a smoke test and requires a meticulous visual inspection of the wiring loom leading to the affected cylinder.

OEM Part Supersession History

• 5038785AA, 5038785AB, 5038785AC → 5038785AD — These are the part numbers for the MDS-style hydraulic lifters. The numbers have been revised over the years due to design updates intended to improve durability and address failure rates.
  Heads up: When replacing lifters due to failure, many mechanics recommend converting to the more robust non-MDS lifters (Mopar P/N 5038784AD) from the 6.4L or Hellcat engines and disabling the MDS system in the PCM.

Diagnostic Flowchart

Real Owner Stories

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

Related OBD-II Codes

• P0306 — Cylinder 6 Misfire Detected. This code will appear during diagnosis if you swap a faulty ignition coil from cylinder 8 to cylinder 6 (the adjacent cylinder on the passenger side bank) and the misfire follows the coil.
• P0300 — Random/Multiple Cylinder Misfire Detected. Often appears alongside P0308, and is specifically noted in Chrysler TSB #18-022-21 regarding PCM software sensitivity to misfire detection.
• P0420 — Catalyst System Efficiency Below Threshold. A severe, flashing-CEL misfire on cylinder 8 dumps unburned fuel into the exhaust, which can quickly damage the catalytic converter and trigger this companion code.
• P0208 — Injector Circuit/Open - Cylinder 8. If the P0308 is caused by a faulty fuel injector or rodent damage to the injector wiring harness (as noted in owner reports), this circuit code may appear alongside the misfire code.

Frequently Asked Questions