P0305 on 2015-2020 Ram 3500: Cylinder 5 Misfire Causes and Fixes (Hemi & Cummins)

What's Unique About the 2015-2020 Ram 3500

For the Ram 3500, the cause of a P0305 code is entirely dependent on which engine you have. The diagnostic path for the 6.4L Hemi V8 (gasoline) is completely different from that of the 6.7L Cummins (diesel). For the Hemi, the issue is typically spark-related (plugs, coils), but can be a sign of a serious internal engine problem like a failed lifter, which is a well-documented issue. For the Cummins, the misfire is almost always fuel-related, with a faulty fuel injector or its wiring being the prime suspect.

Diagnostic Flowchart

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

Generation note: This range covers the end of the fourth generation (2015-2018) and the start of the fifth generation (2019-2020) Ram Heavy Duty trucks. For the 6.7L Cummins, a significant change occurred in 2019 with the introduction of a new compacted graphite iron block and a switch to hydraulic lifters, which have become a known failure point. Additionally, 6.7L Cummins engines from 2007-2012 require injector trim codes to be programmed, while models from 2013-2018 do not. Always verify procedures for your specific model year.

Symptoms You May Notice

• Rough or shaky idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Flashing Check Engine Light (indicates a severe misfire)
• Poor fuel economy
• For 6.7L Cummins: Excessive white or blue-white smoke from the exhaust
• For 6.4L Hemi: A distinct ticking or knocking sound from the engine, which could indicate lifter failure.

Most Likely Causes

1. Failed Ignition Coil (6.4L Hemi) 🔴 High Probability Coil-on-plug ignition systems are common failure points due to constant heat cycles. It's the most frequent cause of a single-cylinder misfire on modern gasoline engines and a very common first step in diagnosis on owner forums.
   How to confirm: Swap the ignition coil from cylinder 5 with another cylinder (e.g., cylinder 1). Cylinder 5 is the third cylinder back on the driver's side. Clear the codes and drive the truck. If the code changes to P0301, the coil is faulty.
   Typical fix: Replace the faulty ignition coil. It is held on by a single 10mm bolt. The OEM Mopar part number is 68238603AA.
   Est. part cost: $40-$80 per OEM coil
2. Failed Fuel Injector (6.7L Cummins) 🔴 High Probability The high-pressure common rail fuel system is sensitive to fuel quality and contamination. Water or debris in the fuel can damage the precise internal components of the injector, making it the most common cause of a misfire on the Cummins.
   How to confirm: A professional diagnosis using a scan tool (like wiTECH or AlfaOBD) to perform a cylinder contribution test is the most accurate method. One can also perform an injector return flow test; the maximum allowable leakage for all injectors combined is 210 mL in 30 seconds. Before replacement, inspect the wiring harness for issues.
   Typical fix: Replace the fuel injector for cylinder 5. This is a complex job that may require programming the new injector's IQA/trim code into the ECM, particularly on 2007-2012 models.
   Est. part cost: $300-$600 for a new Bosch injector
3. Worn Spark Plugs (6.4L Hemi) 🟡 Medium Probability The 6.4L Hemi engine uses two spark plugs per cylinder (16 total). While the recommended change interval is long (up to 100,000 miles), heavy use, towing, or long idle times can shorten their life, leading to a weak spark and misfires.
   How to confirm: After ruling out the ignition coil, remove and inspect the two spark plugs from cylinder 5. Look for a worn electrode, heavy carbon deposits, oil fouling, or an incorrect gap.
   Typical fix: Replace the spark plugs. It is highly recommended to replace all 16 plugs at the same time to ensure even performance.
   Est. part cost: $100-$200 for a full set of 16 plugs
4. Failed Camshaft and Lifters (6.4L Hemi) ⚪ Low Probability The Hemi engines of this era are known to have issues with the hydraulic roller lifters, where the needle bearings can fail. This causes the lifter to seize and grind down the corresponding camshaft lobe, leading to a persistent misfire and a characteristic ticking sound. This is a widely documented failure in owner forums.
   How to confirm: Listen for a loud, rhythmic ticking noise from the engine bay, often called the 'Hemi tick'. A compression test on cylinder 5 will likely show low readings; a healthy cylinder should be around 165-180 PSI, while a failed one might be as low as 40 PSI. Visual inspection requires removing the valve cover to observe rocker arm movement; a lack of movement on an intake or exhaust valve points to this failure.
   Typical fix: This is a major and expensive engine repair that involves replacing the camshaft, all lifters, head gaskets, and related components.
   Est. part cost: $1500-$2500+

Rare But Worth Checking

• Injector Wiring Harness Issue (6.7L Cummins): The injector wiring passes through the valve cover gasket. Over time, heat and vibration can cause the wires to become brittle and break, creating an open circuit for a specific injector. The pass-through connector on the valve cover is a known failure point. This can mimic a failed injector and is worth inspecting before replacing the expensive part.
• Vacuum Leak (6.4L Hemi): A leak in the intake manifold gasket or a vacuum hose near cylinder 5 can lean out the air/fuel mixture enough to cause a misfire. This is less common for a single-cylinder misfire but possible.
• PCM Software Issue: Multiple TSBs, including #1800824 and #1800724, list misfire codes (including P0305) as being potentially resolved by a PCM software update. The TSB indicates the flash addresses misfire detection logic among other issues. If no mechanical fault is found, checking for available updates with a dealer is a valid step.
• Broken Valve Spring (6.4L Hemi): Though less common than lifter failure, a broken valve spring can cause a sudden and severe misfire. This prevents the valve from closing properly, leading to a complete loss of compression on that cylinder. Diagnosis involves a compression test and visual inspection under the valve cover.

Diagnosis Steps

1. Identify your engine (6.4L Hemi or 6.7L Cummins) as the diagnostic path differs completely.
2. For 6.4L Hemi: Start with the ignition system. Swap the ignition coil from cylinder 5 with another cylinder (e.g., cylinder 1). Cylinder 5 is the third cylinder back on the driver's side. Clear the codes and run the engine. If the code changes to P0301, you have a bad coil.
3. For 6.4L Hemi: If the code remains P0305 after the coil swap, inspect the two spark plugs for cylinder 5. Check for wear, damage, or fouling. If they are old or in poor condition, replace all 16.
4. For 6.4L Hemi: If ignition components are good, listen carefully for a 'Hemi tick'. Perform a compression test on cylinder 5. A low reading (e.g., 40 PSI vs. a healthy 165-180 PSI) points towards a mechanical issue like the common cam/lifter failure or a broken valve spring.
5. For 6.7L Cummins: The most likely cause is the fuel injector. Before replacing it, inspect the wiring harness connector at the valve cover for any damage or loose connections. The rear connector serves cylinders 4-6. Consider checking the injector wiring continuity through the valve cover gasket, as this is a known failure point.
6. For 6.7L Cummins: To definitively confirm a bad injector, have a professional perform a cylinder contribution test with a capable scan tool (like wiTECH) or an injector return flow test.
7. For Both Engines: Check for any available Powertrain Control Module (PCM) software updates with a dealership or capable shop, as TSBs indicate this can sometimes resolve misfire detection issues.

Parts You'll Likely Need

• Ignition Coil (6.4L Hemi) (OEM #68238603AA) — This is the most common failure part for a single-cylinder misfire on the Hemi engine.
  Trusted brands: Mopar, NGK, Delphi
  OEM price range: $50-$90
  Aftermarket price range: $30-$75
• Fuel Injector (6.7L Cummins) (OEM #68444791AA (Bosch 0445124047)) — The most probable cause of a P0305 on the Cummins diesel, often due to fuel contamination or high mileage.
  Trusted brands: Bosch (OEM), Mopar, XDP (Reman)
  OEM price range: $450-$700
  Aftermarket price range: $300-$500
• Camshaft and Lifter Kit (6.4L Hemi) — Required for the common 'Hemi tick' failure, where a seized lifter destroys the camshaft lobe. This is a major repair.
  Trusted brands: Mopar, Comp Cams, Texas Speed
  OEM price range: $1000-$1500 (parts only)
  Aftermarket price range: $800-$1200 (parts only)

Related Codes That Often Appear With This One

• P0205 — This code means 'Injector Circuit/Open - Cylinder 5'. Seeing it with P0305 strongly suggests the fuel injector or its wiring is the root cause on either engine.
• P0300 — If the misfire is intermittent or starting to affect other cylinders, the PCM may log P0300 (Random/Multiple Cylinder Misfire) alongside the specific P0305 code.

Technical Service Bulletins (TSBs) & Recalls

• 1800824: Lists P0305-00 - Cylinder 5 Misfire among other codes for 2020 models.
• 1800724: Lists P0305-00 - Cylinder 5 Misfire among other codes for 2019 models.
• 1806623: Lists P0305-00 - Cylinder 5 Misfire among other codes for 2019 models.
• 1810122REVA: Lists P0305-00 - Cylinder 5 Misfire among other codes for 2019 models.
• 18-055-22: Supersedes an earlier TSB for 2020 Ram 3500/4500/5500 models with the 6.7L Cummins, involving a PCM flash to address multiple DTCs, including P0305.

Platform-Specific Known Issues

• Cylinder Location and Firing Order: For diagnosing a P0305, you must correctly identify cylinder 5. On both the 6.4L Hemi and 6.7L Cummins, the cylinders are numbered from front to back. Cylinder 5 is the third cylinder back on the driver's side (left bank). The 6.4L Hemi firing order is 1-8-4-3-6-5-7-2. The 6.7L Cummins I6 firing order is 1-5-3-6-2-4.
• The 'Hemi Tick' and Cam/Lifter Failure: The characteristic 'Hemi tick' is a widely discussed issue in the Ram community. It's a rhythmic ticking or tapping sound from the engine, often more pronounced at idle. While sometimes benign, it is frequently an early warning sign of a failing hydraulic roller lifter. The needle bearings in the lifter can fail, causing the roller to seize and grind a flat spot on the camshaft lobe. This leads to a loss of valve lift, causing a persistent misfire (like P0305) that cannot be fixed by replacing ignition components. This is a major engine repair.

Mechanic-Grade Diagnostic Values

• 6.4L Hemi Ignition Coil Primary Resistance — expected: 0.49 - 0.57 Ohms. Failure: A reading outside this range suggests a faulty primary winding.
• 6.4L Hemi Ignition Coil Secondary Resistance — expected: 9.5 - 11.1 kOhms. Failure: A reading outside this range suggests a faulty secondary winding.
• 6.4L Hemi Engine Compression — expected: 165-180 PSI per cylinder. Failure: A significantly lower reading, like 40 PSI, points to a severe mechanical issue (e.g., cam/lifter failure, broken valve spring).
• 6.7L Cummins Fuel Injector Solenoid Resistance — expected: Less than 5 Ohms, typically 1.5-3.5 Ohms. Failure: High resistance or an open circuit indicates a failed injector solenoid.
• 6.7L Cummins Total Injector Return Flow (Running Test) — expected: Less than 210 mL in 30 seconds at 1,200 RPM and ~26,000 PSI rail pressure.. Failure: Flow greater than 210 mL indicates excessive leakage from one or more injectors.
• 6.7L Cummins Individual Injector Contribution to Return Flow — expected: Isolating one injector should not drop total return flow significantly.. Failure: If blocking off one injector reduces total leakage by more than 40 mL, that injector has excessive leakage.

Scan Tool Commands That Help

• wiTECH or equivalent bidirectional scanner: Cylinder Power Balance Test — For the 6.4L Hemi, this test can confirm cylinder 5 is not contributing power by individually shutting off cylinders and observing RPM drop. Little to no RPM drop when cylinder 5 is deactivated confirms the misfire location electronically.
• wiTECH, AlfaOBD, or other advanced diesel scanner: Cylinder Contribution Test / Injector Kill Test — For the 6.7L Cummins, this function deactivates one injector at a time to see how it affects engine smoothness. It's a primary method for identifying a specific faulty injector electronically.
• wiTECH, Autel, Snap-on, or other professional scan tool: Injector Quantity Adjustment (IQA) / Trim Code Programming — For 2007-2012 6.7L Cummins engines, this is required after replacing a fuel injector. The unique code from the new injector must be entered into the ECM to ensure correct fuel calibration.
• wiTECH or equivalent: Fuel Pressure Override Test — For the 6.7L Cummins, this command forces the fuel rail pressure to a specific high value (e.g., 26,107 PSI) at a set RPM, which is necessary to perform an accurate, by-the-book injector return flow test.

Wiring & Ground Locations

• Cylinder 5 Ignition Coil Connector (6.4L Hemi) — The 3-pin connector on the third ignition coil from the front on the driver's side.. This is the direct connection for the cylinder 5 coil. A damaged connector or wire at this point (for 12V supply, PCM signal, or ground) will cause a P0305.
• Bank 2 Injector Harness Connector (6.7L Cummins) — The rear of the two large electrical connectors on the driver's side of the valve cover.. This single connector provides the electrical connection for injectors 4, 5, and 6. It is a common failure point for corrosion or damage, and a fault here can cause a P0305 or P0205.
• PCM Connector A, Pin 60 (6.7L Cummins) — Pin A60 on the Powertrain Control Module (PCM) harness connector.. This specific pin is the 'INJECTOR 5 CONTROL' wire (Light Blue/Brown). Testing for a signal here can determine if the PCM is commanding the injector to fire, helping to isolate a wiring issue from a faulty PCM driver.
• G105 Ground — Located on the left rear of the cylinder head.. This is a primary engine ground. While a poor connection here would likely cause multiple codes, it can sometimes manifest as a single cylinder misfire due to erratic electrical signals. It's an often-overlooked basic check.

Real Owner Repair Stories

• RamForum.com user (2014 Ram 3500 6.4L Hemi) — Check engine light with a misfire code.
  ✅ What actually fixed it The misfire was caused by a failed lifter. This required a major engine repair to replace the camshaft and lifters.
• YouTube video by 'GQ Auto Diagnostics' (2016 Ram 1500 5.7L Hemi (similar engine architecture)) — Engine runs rough, code P0305.
  ❌ Tried (didn't work) Replacing spark plugs, Verifying ignition coil was good, Verifying injector was working
  ✅ What actually fixed it A compression test showed only 40 PSI on cylinder 5. Removing the valve cover revealed the intake valve was not opening due to a wiped camshaft lobe, caused by a failed lifter.
• RamForum.com user 'quipstad' (6.7L Cummins (year not specified)) — User was installing a tuner and needed to identify injector wiring.
  ✅ What actually fixed it It was confirmed that for the two main injector harness plugs on the driver's side valve cover, the rear connector serves cylinders 4, 5, and 6, while the front connector serves cylinders 1, 2, and 3. This is critical information for diagnosing a wiring fault for P0305.

Model Year Variations Within This Range

• 2019-2020: The 6.7L Cummins engine was significantly updated for the 2019 model year, including a new compacted graphite iron block and a switch from solid tappets to hydraulic roller lifters. This introduced a new potential failure point (lifter failure) that does not exist on the 2015-2018 models.
• 2013-2018: Unlike the earlier 2007-2012 models, 6.7L Cummins engines in this year range do not require injector trim codes (IQA codes) to be programmed into the ECM after an injector replacement.