P0305 on 2019-2025 Ram 1500: Cylinder 5 Misfire Causes and Fixes

What's Unique About the 2019-2025 Ram 1500

On the 2019-2025 Ram 1500, a P0305 code can range from a simple fix to a significant engine problem. While standard ignition component failures are common, these trucks are also subject to specific issues. Several Technical Service Bulletins (TSBs) address software glitches that can cause misfires during cold starts, requiring a PCM update. [18-031-25 REV. A, 18-021-26] More seriously, the 5.7L HEMI has a known weakness in its valvetrain, where a failed MDS lifter can damage the camshaft, 🎬 See how a failed lifter damages the Hemi camshaft. leading to a persistent misfire that isn't fixed by new plugs or coils. Similarly, the 3.6L Pentastar V6 is known for rocker arm bearing failures that can score the camshaft and cause a misfire on a specific cylinder.

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 shaky idle
• Hesitation or stumbling during acceleration
• Flashing or solid Check Engine Light
• Noticeable loss of power
• Engine ticking or valvetrain noise, especially from the driver's side of the engine [09-011-25, 16]
• Reduced fuel economy

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Coil-on-plug systems are common failure points due to engine heat and vibration. Aftermarket coils can also be unreliable, with many owners recommending sticking with genuine Mopar parts.
   How to confirm: Swap the ignition coil from cylinder 5 with another cylinder (e.g., cylinder 3). Clear the codes and drive. If the code changes to P0303, the coil is bad.
   Typical fix: Replace the faulty ignition coil.
   Est. part cost: $40-$80
2. Worn Spark Plugs 🔴 High Probability The 5.7L HEMI uses two spark plugs per cylinder, increasing the chance of a failure. Plugs wear over time, especially past the recommended 100,000-mile service interval. Incorrectly gapped or fouled plugs are a common cause.
   How to confirm: After confirming the coil is good, inspect the spark plugs for cylinder 5. Look for wear, fouling, oil, coolant, or an incorrect gap.
   Typical fix: Replace the spark plugs. It's recommended to replace all plugs at the same time.
   Est. part cost: $50-$150 for a full set
3. Faulty Fuel Injector 🟡 Medium Probability Injectors can become clogged with deposits or fail electronically, preventing the correct amount of fuel from reaching cylinder 5.
   How to confirm: If swapping the coil and plug doesn't work, you can swap the fuel injector from cylinder 5 with another cylinder. This is more involved. If the misfire code moves, the injector is the cause.
   Typical fix: Replace the faulty fuel injector.
   Est. part cost: $70-$150
4. PCM Software Update Needed 🟡 Medium Probability Manufacturer TSBs #18-031-25 REV. A and #18-021-26 specifically mention that misfire codes, including P0305, can be set during cold starts due to software calibration. This is a documented issue that a dealer must address.
   How to confirm: A dealership or qualified shop with access to OEM software (wiTECH) can check if your vehicle's PCM has the latest updates by referencing the TSBs.
   Typical fix: Reprogram the Powertrain Control Module (PCM) with the latest software.
   Est. part cost: $0-$200 (labor cost)
5. Failed Lifter / Worn Camshaft (5.7L HEMI) ⚪ Low Probability The MDS (Multi-Displacement System) lifters in the 5.7L HEMI are a known weak point. Insufficient oiling, especially with extended idling, can cause the lifter's roller to seize and fail, which then grinds down the corresponding camshaft lobe.
   How to confirm: This is often accompanied by a persistent ticking noise ('Hemi Tick') from the driver's side. A compression test and leak-down test are necessary. A visual inspection by removing the valve cover can show if a rocker arm has reduced movement compared to others.
   Typical fix: Requires extensive engine work: replacing the camshaft, all lifters (often with an MDS delete kit), head gaskets, and related components.
   Est. part cost: $800-$2000+
6. Failed Rocker Arm / Worn Camshaft (3.6L Pentastar) ⚪ Low Probability The 3.6L Pentastar engine is known for failures of the rocker arm needle bearings. The bearings fall out, causing the rocker arm to collapse and damage the camshaft lobe, resulting in a misfire and ticking noise.
   How to confirm: A distinct ticking or tapping noise from the top of the engine is the primary symptom. Diagnosis requires removing the valve cover to inspect the rocker arms and camshaft lobes for visible damage and excessive play.
   Typical fix: Replace all rocker arms on the affected cylinder head, the damaged camshaft, and often the lifters as a preventative measure.
   Est. part cost: $500-$1500

Rare But Worth Checking

• Intake Manifold Gasket Leak: A vacuum leak near the cylinder 5 intake runner can lean out the air/fuel mixture, causing a misfire. Forum users suggest checking intake manifold bolt torque, as they can loosen over time. A smoke test is the best way to confirm a leak.
• Cracked Exhaust Manifold: A common issue on Ram 1500s is a cracked exhaust manifold or broken manifold bolts, which can cause a ticking noise on cold starts that might be mistaken for a lifter tick. In some cases, the resulting change in exhaust pressure can be misinterpreted by sensors and contribute to a misfire code.
• Damaged Valve Seat: In some cases, the valve seat in the cylinder head can deteriorate, causing a loss of compression and a persistent misfire that isn't resolved by replacing ignition or fuel parts. A leak-down test will confirm this. A borescope inspection may reveal visible damage to the valve seat.

Diagnosis Steps

1. Read the code with an OBD-II scanner and confirm P0305 is present. Note if the check engine light is steady or flashing.
2. Check for any applicable TSBs, especially related to cold start misfires. [18-031-25 REV. A, 18-021-26]
3. Locate cylinder 5 (on the 5.7L HEMI, it's the third cylinder from the front on the driver's side; on the 3.6L V6, it's the middle cylinder on the driver's side).
4. Swap the ignition coil from cylinder 5 with an adjacent, easy-to-access cylinder (like cylinder 3).
5. Clear the codes, start the engine, and drive until the check engine light returns. If the code is now P0303, the ignition coil is bad. Replace it.
6. If the code remains P0305, inspect and/or swap the spark plug(s) from cylinder 5 with the other cylinder. Repeat the test. If the code moves, the spark plug was the issue.
7. If the code still remains P0305, listen carefully to the engine at idle. Use a mechanic's stethoscope or a long screwdriver near the cylinder 5 valve cover to listen for a distinct ticking sound, which could indicate a valvetrain problem.
8. If ignition parts are ruled out and a tick is present, the next step is a mechanical evaluation. Perform a compression test and a leak-down test on cylinder 5 to check for bad rings, valves, or a failed lifter/cam.
9. If tests point to a mechanical issue, remove the valve cover for a visual inspection of the rocker arms, valve springs, and camshaft lobes for wear or damage.

Parts You'll Likely Need

• Ignition Coil (OEM #68238603AA) — This is the most common and easiest-to-diagnose cause of a single-cylinder misfire.
  Trusted brands: Mopar, NGK, Denso
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Spark Plugs (OEM #SP143877AA (Champion Copper for 5.7L)) — Spark plugs are a routine maintenance item and a frequent cause of misfires as they wear out.
  Trusted brands: Champion, NGK
  OEM price range: $8-$12 per plug
  Aftermarket price range: $4-$8 per plug
• Camshaft and Lifter Kit (5.7L HEMI) — Required when the 'Hemi tick' is diagnosed as a failed lifter and worn camshaft lobe, a known issue on the 5.7L engine.
  Trusted brands: Mopar, Sealed Power, Melling
  OEM price range: $1200-$1800
  Aftermarket price range: $600-$1000

Related Codes That Often Appear With This One

• P0300 — If the misfire becomes more widespread due to a systemic issue like a major vacuum leak, failing fuel pump, or significant valvetrain damage, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0305.
• P219A — Air-Fuel Ratio Imbalance. This code can appear with a P0305 if a mechanical failure (like a bad cam/lifter) causes low compression, leading to unburnt fuel in the exhaust that the PCM interprets as an imbalance.

Technical Service Bulletins (TSBs) & Recalls

• 18-031-25 REV. A: Addresses cold start misfire codes P0300-P0306 and recommends a PCM reprogram.
• 18-021-26: Also relates to cold start misfires and recommends a PCM software update.
• 09-011-25: Connects valvetrain noise complaints with misfire DTCs, pointing towards mechanical issues.
• 18-006-24: Lists P0305 among other misfire codes that may be addressed by software updates or diagnostics.
• 08-087-25: Notes that P0305 can be set along with catalyst efficiency codes (P0420/P0430), indicating a severe misfire may be damaging the catalytic converter.

Platform-Specific Known Issues

• Cold Start Misfires: TSB #18-031-25 REV. A and #18-021-26 specifically note that software improvements are available to address misfire faults (P0300-P0306) that occur during the cold start catalyst heating phase. The fix is a PCM reprogram.
• HEMI Lifter/Cam Failure: A persistent P0305, often accompanied by a ticking sound, can be a symptom of the notorious 'Hemi tick,' which is a failing MDS lifter destroying the camshaft. This is a major engine repair. TSB #09-011-25 also notes that misfire codes can be associated with customer complaints of valvetrain noise.
• Pentastar Rocker Arm Failure: On the 3.6L V6, a P0305 code accompanied by a ticking noise is very often caused by a failed rocker arm bearing on cylinder 5, which in turn damages the camshaft.

Mechanic-Grade Diagnostic Values

• Fuel Pressure (Key On, Engine Off) — expected: Approximately 58-60 PSI.. Failure: Significantly lower pressure can indicate a weak fuel pump. Pressure that doesn't hold could be a leak.
• Engine Compression (5.7L HEMI) — expected: A healthy cylinder should show 110-150 PSI or higher.. Failure: A reading of 40 PSI, as noted in one diagnostic case, points to a major mechanical issue like a stuck valve or failed lifter/cam lobe. The key is consistency; readings should be close across all cylinders.
• Ignition Coil Primary/Secondary Resistance — expected: While specific OEM values are not published for technicians, a common check is to compare the resistance of the suspected bad coil with a known good coil. A significant deviation indicates a faulty coil.. Failure: An open circuit (infinite resistance) or a reading that is substantially different from other coils on the engine.

Scan Tool Commands That Help

• wiTECH or high-end bidirectional scanner: Cylinder Power Balance Test — This test allows the technician to disable one cylinder at a time and observe the corresponding drop in RPM. If disabling cylinder 5 results in little or no change in RPM, it confirms that cylinder is not contributing power, pinpointing the misfire without having to swap parts initially.
• wiTECH or high-end bidirectional scanner: View Misfire Counters — Live data can show misfire counts for each cylinder in real-time. This is useful to confirm the misfire is actively occurring on cylinder 5 and to see if other cylinders are misfiring intermittently, which might suggest a more systemic problem than a single bad coil.

Wiring & Ground Locations

• Engine to Body/Frame Ground Strap — A primary ground strap typically connects from the back of the cylinder head to the firewall or frame rail.. A corroded or loose main engine ground can cause erratic electrical behavior, including weak spark. While it usually causes multiple random misfires (P0300), it can sometimes manifest as a single-cylinder misfire initially. Ensuring this connection is clean and tight is a crucial, often overlooked, electrical check.
• Cylinder 5 Ignition Coil Connector — On the 5.7L HEMI, it's the 3-pin connector on the third ignition coil from the front on the driver's side.. This is the point for testing voltage and ground signals to the coil. The pins are typically: 1) 12V+ from the ASD relay, 2) Coil driver signal from the PCM, and 3) Ground. A faulty connection or damaged wire here will directly cause a P0305.

Real Owner Repair Stories

• Video Service Information YouTube Channel (2012 Ram 1500 5.7L HEMI with 105,000 miles) — Check engine light on with a P0305 code and an audible engine tick noise from the cylinder 5 area.
  ❌ Tried (didn't work) The diagnosis immediately pointed to a mechanical issue due to the ticking noise.
  ✅ What actually fixed it The root cause was a failed lifter on cylinder 5 (non-MDS cylinder), which had a scored roller with flat spots. This failure subsequently destroyed the corresponding lobe on the camshaft. The recommended fix was a new engine due to additional wear found on the cam bearings.
• GQ Auto Diagnostics YouTube Channel (2016 Ram 1500 5.7L HEMI) — Engine runs rough, P0305 code present.
  ❌ Tried (didn't work) Replaced spark plugs (they were filthy but not the cause)., Confirmed ignition coil was good., Confirmed fuel injector was working.
  ✅ What actually fixed it A compression test showed very low compression (40 PSI) on cylinder 5. Removing the valve cover revealed the intake valve rocker arm for cylinder 5 was not moving, while the exhaust was. This confirmed a collapsed lifter and/or a wiped camshaft lobe. The fix requires head removal to replace the lifters and camshaft.
• RamForum.com user (2012 Ram 1500 Sport 5.7L HEMI with 145,000 miles) — P0305, more noticeable under load.
  ❌ Tried (didn't work) A local shop misdiagnosed it as bad rings and quoted a $14,000 engine replacement., Owner performed his own compression test and got a healthy 180 PSI, ruling out rings., Coil pack, spark plugs, and fuel injector were swapped and tested good.
  ✅ What actually fixed it The user suspected a cam/lifter issue, which is the next logical step after ruling out compression, spark, and fuel. The thread points towards this being the final diagnosis, a common outcome for these symptoms on HEMI engines.
• Video Service Information YouTube Channel (2016 Ram 1500 5.7L HEMI) — P0305 misfire, audible ticking noise from the left bank.
  ❌ Tried (didn't work) Initial diagnosis focused on the misfire code.
  ✅ What actually fixed it A leak-down test showed 60% leakage through the intake side. A borescope inspection revealed the intake valve seat for cylinder 5 was deteriorated and delaminating. The fix required removing the cylinder head to be machined or replaced. The technician also noted that with the head off, it's the perfect time to inspect the known-to-fail lifters and camshaft.

OEM Part Supersession History

• 56029129AF, 68060346AA → 68238603AA — Standard part evolution for improved reliability or manufacturing efficiency.
  Heads up: The newer part number 68238603AA is the correct, backward-compatible replacement. Using older stock is not recommended.

Model Year Variations Within This Range

• 2019+: The introduction of the 5.7L HEMI with eTorque adds a layer of complexity. While the fundamental causes of P0305 (spark, fuel, compression) remain the same, the eTorque system's 48V battery and motor-generator unit can introduce unique electrical issues. TSB #18-031-25 REV. A, which addresses cold start misfires, is particularly relevant to these newer models. [18-031-25 REV. A]