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 seriously. While it can be caused by simple ignition parts, it is also a very common 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 lubrication issues or wear. This causes the roller on the lifter to seize and grind down the camshaft lobe, preventing the valve from opening properly and resulting in a permanent misfire. Cylinder 8, being at the rear of the engine, is one of the cylinders sometimes cited as being prone to these oiling-related failures. Ignoring the initial ticking sound that often accompanies lifter wear can lead to a P0308 code and significant engine damage.

Diagnostic Flowchart

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

Symptoms You May Notice

• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Flashing or solid Check Engine Light
• Noticeable loss of engine power
• Engine may disable the MDS (Multi-Displacement System) and remote start feature.
• A ticking or fluttering noise from the engine bay, which could indicate a mechanical valvetrain problem. This is often called the 'Hemi tick' and may be more pronounced at idle when the engine is warm.
• An exhaust leak sound, which can be confused with the 'Hemi tick' but is often caused by broken exhaust manifold bolts, another common issue.

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Heat and vibration in the engine bay can cause ignition coils to fail over time. It's a common wear-and-tear item and a frequent cause of a single-cylinder misfire.
   How to confirm: Swap the ignition coil from cylinder 8 with another cylinder (e.g., cylinder 6, which is easier to access on the same passenger-side bank). Clear the codes and drive the truck. If the code changes to P0306, the ignition coil is the culprit.
   Typical fix: Replace the faulty ignition coil. Many owners choose to replace all 8 coils at the same time as preventative maintenance, especially on higher mileage vehicles.
   Est. part cost: $25-$60 per coil
2. Worn Spark Plugs 🔴 High Probability The 5.7L HEMI uses two spark plugs per cylinder (16 total). Worn, fouled, or improperly gapped plugs are a very common cause of misfires. The recommended service interval should be followed closely.
   How to confirm: After ruling out the coil, remove the two spark plugs from cylinder 8. Inspect them for wear, oil fouling, or damage. A cracked porcelain insulator can also cause a misfire.
   Typical fix: Replace the spark plugs. It is highly recommended to replace all 16 spark plugs at the same time to ensure balanced engine performance.
   Est. part cost: $50-$150 for a set of 16
3. Failed Lifter and/or Damaged Camshaft 🟡 Medium Probability The 5.7L HEMI from this era is notorious for lifter failures, especially on the MDS cylinders. Insufficient lubrication at idle and low RPMs, combined with the complexity of the MDS lifters, can cause the lifter's roller bearing to fail. The seized roller then grinds away the camshaft lobe, leading to a loss of valve lift and a persistent misfire.
   How to confirm: If swapping the coil, plug, and injector does not resolve the P0308 code, this is the next logical suspect, especially if a ticking noise is present. A definitive diagnosis involves removing the passenger-side valve cover to inspect the rocker arms and pushrods for cylinder 8. A loose or dislodged rocker arm is a clear sign of a collapsed lifter.
   Typical fix: This is a major engine repair that involves replacing the camshaft, all 16 lifters, head gaskets, and other related components. Many owners and shops opt to install an MDS delete kit, which uses simpler, more robust non-MDS lifters (like those from the 6.4L or Hellcat engines) and requires a PCM tune to disable the MDS function.
   Est. part cost: $800-$2500 for a complete cam and lifter kit
🎬 Watch: A 30-minute walkthrough of the camshaft and lifter replacement.
4. Faulty Fuel Injector ⚪ Low Probability
   How to confirm: If the coil and plug are good, you can swap the fuel injector from cylinder 8 with another cylinder. If the misfire code follows the injector, the injector is faulty. You can also listen to the injector with a mechanic's stethoscope to ensure it's clicking like the others.
   Typical fix: Replace the clogged or failed fuel injector. Some owners have had success with using a strong fuel system cleaner as a first step for an intermittent misfire.
   Est. part cost: $40-$100

Rare But Worth Checking

• Intake Manifold Gasket Leak: A vacuum leak near the intake runner for cylinder 8 can lean out the air/fuel mixture and cause a misfire. This can sometimes be detected by spraying brake cleaner near the gasket with the engine running and listening for a change in idle speed. A smoke test is a more definitive way to find a leak.
• Wiring Harness Issue: Rodents can chew through wires, or wires can become chafed and shorted, interrupting the signal to the ignition coil or fuel injector for cylinder 8. There is a known TSB for other GM vehicles regarding harness chafe against the shock tower, control arm, or brackets, which is a plausible issue on Rams as well.
• PCM (Powertrain Control Module) Issue: As mentioned in TSBs for other model years (#1800624, #1814522), a software update may be needed to address misfire detection logic. TSB #18-093-15 also notes a specific condition where a misfire can be set on a cold start if the vehicle is immediately put in drive. In very rare cases, the driver circuit within the PCM itself can fail.
• Valve Cover Gasket Leak: A leaking valve cover gasket can allow oil to pool in the spark plug tube for cylinder 8, fouling the spark plugs and causing the ignition coil boot to degrade, leading to a misfire.

Diagnosis Steps

1. Verify the code is P0308 using an OBD-II scanner. Note if the check engine light is solid or flashing.
2. Check the engine oil level and condition. Low or dirty oil can contribute to lifter issues.
3. Locate cylinder 8. On the 5.7L HEMI, it is the rearmost cylinder on the passenger side of the engine (front to back: 2, 4, 6, 8).
4. Swap the ignition coil from cylinder 8 with the coil from cylinder 6 (the next one forward on the same bank). Clear the codes and drive the vehicle. If the code returns as P0306, you have a bad ignition coil.
5. If the code remains P0308, inspect the spark plug tube for oil. If oil is present, the valve cover gasket is leaking. Then, swap the two spark plugs from cylinder 8 with those from cylinder 6. If the code moves to P0306, you had bad spark plugs.
6. If the code remains P0308, inspect the wiring and connector for the ignition coil and fuel injector on cylinder 8 for any damage, corrosion, or signs of rodents.
7. The next step is to test the fuel injector. This can be done by swapping it with another cylinder, similar to the coil test, or by listening to it with a stethoscope to confirm it is clicking.
8. If all ignition and fuel components test good, the cause is likely mechanical. Listen carefully for a persistent ticking sound (the 'Hemi tick'), especially at idle.
9. Perform a compression test on cylinder 8 and compare it to other cylinders. A significantly lower reading points towards a valvetrain or internal engine problem.
10. If compression is low or a tick is present, the final step is to remove the passenger-side valve cover and visually inspect the valve springs and rocker arms for cylinder 8 as the engine is slowly rotated by hand. A loose, dislodged, or stationary rocker arm indicates a collapsed lifter and wiped camshaft lobe.

Parts You'll Likely Need

• Ignition Coil (OEM #56029129AF)

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or starting to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0308. A P0300 code appearing with a single cylinder misfire is a strong indicator of a potential lifter/camshaft issue.

Technical Service Bulletins (TSBs) & Recalls

• TSB #1800624 / #1814522: Relates to newer models but indicates that PCM software updates can be issued to refine misfire detection logic.
• TSB #18-093-15: Notes that on some models, a misfire code (P0300-P0308) can be set during a cold start if the driver immediately shifts into drive.
• TSB #21-NA-149 (Referenced for GM, but relevant concept): Describes engine wire harness chafing against chassis components like the control arm and shock tower, which can cause shorts leading to various issues, including misfires.

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 attributed to a combination of oil starvation to the lifters at low RPM/idle and the mechanical complexity of the MDS lifters. Preventative measures discussed by owners include more frequent oil changes with high-quality 5W-20 synthetic oil, avoiding excessive idling, and electronically disabling the MDS system.
• Broken Exhaust Manifold Bolts: The heat cycles of the HEMI engine often cause the exhaust manifold bolts to break, creating an exhaust leak. The resulting ticking sound is frequently confused for lifter tick. An exhaust leak is typically loudest on a cold start and may diminish as the metal expands, while lifter tick is often constant or worsens as the engine warms up.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.558 - 0.682 Ohms at 70-80°F (21-27°C).. Failure: A reading outside this range indicates a faulty coil winding.
• Fuel Injector Resistance — expected: 10 - 18 Ohms.. Failure: A reading significantly outside this range, or that differs greatly from other injectors, points to a bad injector.
• Fuel Pressure (at fuel rail) — expected: 59 PSI +/- 5 PSI.. Failure: Pressure below 54 PSI indicates a weak fuel pump or leak; pressure above 64 PSI could indicate a regulator problem.
• Spark Plug Gap — expected: 1.1 mm (0.043 in.).. Failure: An incorrect gap can cause weak spark and lead to misfires.

Hidden / Shadow Codes Worth Checking

• Mode 6, Test ID $82, Comp ID $08: This is not a 'code' but a diagnostic mode. On advanced scan tools, accessing Mode 6 data can show raw misfire counts for each cylinder, including cylinder 8 (Comp ID $08). This allows a technician to see if misfires are occurring even if they aren't frequent enough to set a P0308 code yet. (see via An OBD-II scan tool that supports Mode 6 diagnostics.)

Scan Tool Commands That Help

• wiTECH (or equivalent professional scanner): Cylinder Contribution Test / Injector Kill Test — Used to pinpoint a weak cylinder when the cause is not obvious. The tool disables one cylinder at a time and measures the corresponding drop in engine RPM. A cylinder with a smaller RPM drop is not contributing as much power as the others.
• wiTECH (or equivalent professional scanner): Actuate ASD Relay — This command forces the Auto Shutdown (ASD) relay on, allowing a technician to test for power at the ignition coil and fuel injector connectors with a test light, verifying the integrity of the power supply circuit.

Wiring & Ground Locations

• Engine Ground Straps — There is a primary 3-point ground strap located on the rear of the engine block connecting to the firewall. Shorter ground straps are also often found on the valve covers or behind the cylinder heads.. A poor ground connection can introduce electrical noise and cause unstable sensor readings or weak spark, leading to misfire codes.
• Cylinder 8 Ignition Coil Driver — On the PCM connector. The specific pin and wire color can be found in the factory service manual wiring diagrams for the specific model year. For example, on a 2017 model, this is often a specific colored wire leading to a numbered pin on one of the main PCM connectors.. To diagnose a potential PCM or wiring issue, a technician must test for a signal from the PCM to the coil. Knowing the pin location is essential for this test.
• Cylinder 8 Fuel Injector Driver — On the PCM connector. Similar to the coil driver, the exact pin number and wire color are year-specific and must be verified with a wiring diagram.. If the injector is not the issue, testing the control circuit back to the PCM is the next step. This requires knowing the correct pin to test for the injector pulse signal.

Real Owner Repair Stories

• Reddit user 'coffeedrinker2018' and 'BinkyBass' (2011 Dodge Ram 1500 5.7L with 357,000 km) — Rough running, P0308 code.
  ❌ Tried (didn't work) New spark plugs, Swapping coil pack with cylinder 6, New fuel injector on cylinder 8
  ✅ What actually fixed it Another user reported the final fix for a similar scenario was finding and repairing an injector wire that had been chewed by a rodent. The damage was only found after close inspection of the wiring harness.
• RamForum.com user 'kobx02' and 'Wild one' (2015 Ram 1500 5.7L with 98k miles) — Intermittent P0308 code, remote start would shut off.
  ❌ Tried (didn't work) Replacing all spark plugs, Swapping cylinder 8 and 7 components (assumed coil/plug)
  ✅ What actually fixed it A responding user with a similar multi-year issue on cylinders 3 and 7 reported that three consecutive treatments with Red Line SI-1 fuel system cleaner finally resolved their misfire and restored fuel economy.
• YouTube channel 'smoran2006' (2006 Ram 1500 with 245,000 miles (similar engine design and failure mode)) — P0308 code, engine ticking noise.
  ❌ Tried (didn't work) Changing the spark plug, Swapping ignition coils
  ✅ What actually fixed it The owner removed the valve cover and discovered the rocker arm for one of the valves on cylinder 8 had completely fallen off and was lying in the head. This was caused by a collapsed lifter, preventing the valve from opening and causing the misfire.

"I Checked Everything" — The Actual Cause

• A common scenario for P0308 on the 5.7L HEMI is for all basic ignition and fuel tests to check out, leaving the owner confused. Many owners report swapping coils, plugs, and even injectors with no change in the code. This often points to the root cause being mechanical (cam/lifter failure) or a subtle electrical fault (chafed wire), which standard diagnostic procedures like a smoke test for vacuum leaks would not uncover. The diagnosis then requires more advanced steps like a compression test or physically inspecting the valvetrain.

When the Usual Fixes Don't Work

• While the most common fixes for P0308 are ignition-related, many owners find themselves chasing the problem after these parts are replaced. In a Reddit thread, a 2011 Ram owner had already replaced the plug, coil, and injector for cylinder 8, but the misfire persisted, forcing them to look for less common electrical or mechanical causes. Another forum user with an intermittent P0308 on a 2015 model found that after trying part swaps, the issue was ultimately resolved with several rounds of a potent fuel system cleaner, suggesting a stubborn clog in the injector that swapping did not initially fix. These cases highlight that if a tune-up doesn't solve the code, the root cause can range from the severe (camshaft failure) to the subtle (wiring damage or stubborn deposits).

OEM Part Supersession History

• 5038785AA, 5038785AB, 5038785AC → 5038785AD — These are part numbers for the 5.7L HEMI MDS lifters. Later revisions aim to improve the durability of the lifter's needle bearings, which were a known weak point.
  Heads up: When replacing a failed lifter, the camshaft lobe must be inspected for damage. Installing a new lifter on a damaged cam will cause immediate failure of the new part.
• 56029129AA, 56029129AB, 56029129AF, 68060346AA → 68238603AA — Standard part evolution for the ignition coils, aimed at improving reliability and manufacturing consistency.

Model Year Variations Within This Range

• 2013-2018 vs 2011-2012: The 2013 model year marked a significant refresh, introducing the 8-speed automatic transmission and updates to the engine management system. The tone rings on the crankshaft and camshaft, which are critical for ignition and fuel timing, are different between the 2011-2012 and 2013+ models. This means a complete engine from a 2013+ truck is not a direct drop-in replacement for a 2011-2012 truck without also swapping the corresponding electronics or engine components.