P0301 on 2015-2020 Ram 3500: Cylinder 1 Misfire Causes and Fixes (HEMI & Cummins)

What's Unique About the 2015-2020 Ram 3500

For the Ram 3500, the cause of a P0301 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 a simple ignition component, but it can be a symptom of a more serious internal engine problem like a failed lifter, known as the 'Hemi tick'. For the Cummins, the problem is almost always fuel-related, pointing directly to the high-pressure fuel injector for cylinder 1. In some cases for the Cummins, multiple TSBs indicate the code can be triggered by a software anomaly that requires a PCM reflash to fix. The provided NHTSA TSBs #1800824, #1800724, and others confirm that P0301 can be set along with a host of other codes, which can sometimes be resolved with a software update.

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 fourth generation (2015-2018) and the redesigned fifth generation (2019-2020) Ram 3500. While the primary causes for P0301 are consistent, the 2019-2020 6.7L Cummins models use a Bosch CP4.2 high-pressure fuel pump which was subject to a safety recall (NHTSA 21V-880) as it is known to be failure-prone and can send debris into the fuel system, causing injector damage.

Symptoms You May Notice

• Check Engine Light is on or flashing
• Rough or shaking engine at idle
• Hesitation or stumbling during acceleration
• Loss of engine power
• Increased fuel consumption
• Hard starting or extended crank time
• White or black smoke from the exhaust (more common on Cummins)
• Loud, rhythmic ticking or clattering noise from the engine (potential lifter failure on HEMI)

Most Likely Causes

1. Faulty Ignition Coil (6.4L HEMI Only) 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are exposed to extreme engine heat and vibration, leading to eventual failure of the internal windings. Moisture intrusion from engine washing or rain can also cause the coil to short out.
   How to confirm: Swap the ignition coil from cylinder #1 with another cylinder (e.g., cylinder #3). Clear the codes. If the misfire code changes to P0303, the coil is faulty.
   Typical fix: Replace the failed ignition coil. It is recommended to apply dielectric grease to the new coil boot.
   Est. part cost: $40-$90
2. Faulty Fuel Injector (6.7L Cummins Only) 🔴 High Probability → Shop Fuel Injector The high-pressure common rail fuel system operates under extreme pressure, making injectors a common wear item sensitive to fuel quality. Debris from a failing CP4.2 fuel pump (2019-2020 models) is a known cause of injector failure.
   How to confirm: A professional scan tool can perform an injector contribution test or check injector balance rates to identify the faulty injector. A user on Reddit reported a P0301 code immediately after a fuel filter change, suggesting air in the lines can temporarily trigger the code. An injector return flow test can also be performed; any single injector contributing more than 40 mL of return fuel is considered excessive.
   Typical fix: Replace the faulty fuel injector and the high-pressure connector tube. This is an involved repair that may require professional service. The new injector's IQA code must be programmed into the ECM.
   Est. part cost: $350-$700
3. Worn or Fouled Spark Plugs (6.4L HEMI Only) 🔴 High Probability → Shop Spark Plug The 6.4L HEMI uses two spark plugs per cylinder (16 total), which are a routine maintenance item with a 100,000-mile service interval. An oil leak from a valve cover gasket can also foul the plugs, causing a misfire.
   How to confirm: After ruling out the ignition coil, remove and inspect both spark plugs from cylinder #1. Look for a worn electrode, cracks, or heavy carbon/oil deposits.
   Typical fix: Replace the spark plugs. It is best practice to replace all 16 plugs if they are near their service interval. Ensure they are gapped correctly (typically .043-.044 inches) and torqued to spec (around 10-15 ft-lbs).
   Est. part cost: $80-$150 for a full set
4. Camshaft/Lifter Failure (6.4L HEMI Only) 🟡 Medium Probability → Shop Engine Camshaft HEMI engines, particularly those with MDS (Multi-Displacement System), are known for a specific type of failure where the roller bearings on a lifter seize. This grinds down the camshaft lobe, causing a persistent misfire. This is often referred to as the 'Hemi tick'.
   How to confirm: A persistent P0301 code that does not resolve after replacing the coil and plugs, accompanied by a loud, rhythmic ticking or clattering noise, is a classic symptom. A mechanic will need to perform a physical inspection of the camshaft and lifters.
   Typical fix: This is a major and expensive repair requiring the replacement of the camshaft, all lifters (MDS and non-MDS), head gaskets, and related components. Some owners on forums report shop quotes of $5,000 or higher for this job.
   Est. part cost: $1500-$2500+ for parts alone.

Rare But Worth Checking

• Low Engine Compression: If ignition and fuel system checks don't find the issue, a mechanical problem like a burnt valve, leaking head gasket, or damaged piston rings could be the cause. This is confirmed with a compression or leak-down test. One forum user with a P0301 on a 6.4L HEMI experienced a seized motor, indicating a catastrophic internal failure.
• Injector Wiring Harness Issue (6.7L Cummins): The injector wiring passes through the valve cover gasket, and the wires can become brittle and break over time from heat and vibration, causing an open circuit to the injector. Pigtail repair harnesses are available (e.g., Fleece Performance FPE-HAR-CUMM-INJ-PT) to fix a broken connector without replacing the entire harness.
• PCM Software Anomaly (6.7L Cummins): Multiple Technical Service Bulletins (TSBs), including #1800824 and #1800724, list P0301 along with many other DTCs that can be resolved by updating the Powertrain Control Module (PCM) software. This suggests the code can sometimes be triggered erroneously by software glitches, especially if seen with codes like P0607 or P20E8.

Diagnosis Steps

1. Identify your engine: 6.4L HEMI (Gas) or 6.7L Cummins (Diesel). The steps are completely different.
2. For 6.4L HEMI: Start by swapping the ignition coil from cylinder #1 (front driver's side) with another cylinder (e.g., #3). Clear the codes and see if the misfire follows the coil (e.g., P0303 appears). If it does, the coil is bad.
3. For 6.4L HEMI: If the coil is good, inspect the two spark plugs from cylinder #1 for wear, damage, or oil fouling. Replace if necessary.
4. For 6.4L HEMI: If plugs and coil are good, listen carefully for a rhythmic ticking noise that could indicate lifter failure. At this point, a compression test is recommended to check for mechanical engine health.
5. For 6.7L Cummins: Diagnosis usually requires a professional scan tool to perform a cylinder contribution test to confirm the misfire is on cylinder #1.
6. For 6.7L Cummins: Inspect the wiring harness and connector for the cylinder #1 fuel injector for any visible damage or corrosion. Check for continuity if damage is suspected.
7. For 6.7L Cummins: If wiring is intact and tests point to the injector, it will likely need to be replaced. Check vehicle history for TSBs related to PCM updates, as a reflash may solve the issue.

Parts You'll Likely Need

• Ignition Coil (6.4L HEMI) (OEM #5149199AA) — This is the most common failure point for a single-cylinder misfire on the HEMI engine.
  Trusted brands: Mopar, NGK, Delphi
  OEM price range: $60-$100
  Aftermarket price range: $40-$75
• Fuel Injector (6.7L Cummins, 2013-2018) (OEM #Mopar R8210512AA / Bosch 0445120342) — This is the most probable cause of a P0301 on the Cummins diesel engine. Part numbers differ for pickup vs. cab & chassis models.
  Trusted brands: Bosch, Mopar
  OEM price range: $450-$700
  Aftermarket price range: $350-$550
• Spark Plugs (6.4L HEMI) (OEM #NGK LZTR6AP11EG) — Worn or fouled spark plugs are a common maintenance item and a frequent cause of misfires. The 6.4L HEMI requires 16 plugs.
  Trusted brands: NGK, Champion
  OEM price range: $10-$15 per plug
  Aftermarket price range: $5-$10 per plug

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or affects other cylinders, the PCM may log a P0300 (Random/Multiple Cylinder Misfire) code.
• P0201 — This code indicates a fault in the fuel injector circuit for cylinder 1. If seen with P0301, it strongly points to a problem with the injector or its wiring, not compression.
• P0302, P0303, P0304, etc. — The provided NHTSA Technical Service Bulletins list multiple cylinder misfire codes together, suggesting a systemic issue like a PCM software fault could trigger multiple codes at once.

Technical Service Bulletins (TSBs) & Recalls

• TSB #1800824 (January 25, 2024): For 2020 Ram 3500/4500/5500 with 6.7L Cummins, addresses a MIL with numerous DTCs including P0301-P0306. The fix is a PCM software update to improve engine performance, idle stability, and correct false DTCs.
• TSB #1800724 (January 25, 2024): Similar to the above TSB, but for 2019 models with the 6.7L Cummins, also recommending a PCM reflash to address a list of codes including P0301.
• NHTSA Recall 21V-880 (Y78): Affects 2019-2020 Ram 2500/3500 trucks with the 6.7L Cummins. The high-pressure CP4.2 fuel pump can fail, sending debris through the fuel system and causing injector failure and engine stalls.

Platform-Specific Known Issues

• The 'Hemi Tick' leading to P0301: On the 6.4L HEMI, a P0301 code combined with a distinct ticking sound is a strong indicator of a failed lifter that is damaging the camshaft. This is a well-documented, widespread issue. A user on RamForum.com described having a P0301 and a 'clatter' sound, with another user replying that their truck with the same symptoms ended up with a seized engine. This is not a normal engine noise and requires immediate attention to avoid catastrophic engine failure.
• Cummins Injector Failure vs. Wiring: For the 6.7L Cummins, P0301 almost always points to the #1 fuel injector. However, before spending hundreds on a new injector, it's worth inspecting the injector wiring harness where it passes through the valve cover gasket. These wires can become brittle and break, causing an identical code. A pigtail repair kit is a much cheaper fix if a broken wire is found.
• False Misfire Codes from PCM Software: For 2019 and 2020 Cummins models, in particular, Ram has issued TSBs (like 18-008-24) that address a list of fault codes, including P0301, that may be set incorrectly. The prescribed fix is a PCM software update, which can only be performed by a dealer. This should be considered if no obvious mechanical or fuel system fault can be found.

Mechanic-Grade Diagnostic Values

• 6.4L HEMI Ignition Coil Primary Resistance — expected: 0.49 - 0.57 Ohms. Failure: A reading outside this range indicates a faulty primary winding.
• 6.4L HEMI Ignition Coil Secondary Resistance — expected: 9.5 - 11.1 kOhms. Failure: A reading outside this range indicates a faulty secondary winding.
• 6.7L Cummins Injector Return Flow (Running Test) — expected: Less than 210 mL in 30 seconds. Failure: Total return flow greater than 210 mL indicates excessive leakage from one or more injectors.
• 6.7L Cummins Injector Return Flow (Cranking/No-Start Test) — expected: Less than 40 mL in 10 seconds. Failure: Return flow greater than 40 mL indicates an injector is leaking badly enough to prevent starting.
• 6.7L Cummins Individual Injector Contribution to Return Flow — expected: Should not drop total return by more than ~40 mL when isolated. Failure: If blocking off a single injector reduces total return flow by more than 40 mL, that specific injector is faulty.

Scan Tool Commands That Help

• wiTECH or equivalent professional scanner: Cylinder Contribution / Power Balance Test — Used on both HEMI and Cummins engines to electronically disable individual cylinders. If disabling cylinder #1 causes no change in engine RPM or smoothness, it confirms cylinder #1 was not contributing power, verifying the misfire location.
• wiTECH or equivalent professional scanner: Fuel Pressure Override Test (6.7L Cummins) — This function commands the fuel system to maximum pressure (approx. 26,000 PSI) at a set RPM (1200 RPM) to perform the running injector return flow test under controlled conditions.
• wiTECH or equivalent professional scanner: Program IQA Codes (6.7L Cummins) — After replacing a fuel injector on a 6.7L Cummins, the unique Injector Quantity Adjustment (IQA) code from the new injector must be programmed into the ECM for proper fueling calculations.

Wiring & Ground Locations

• Cummins Injector Harness Connectors — On the 6.7L Cummins, there are two main injector harness connectors located on the driver's side of the valve cover. The front connector serves cylinders 1-3, and the rear connector (towards the firewall) serves cylinders 4-6.. To test the wiring for the cylinder #1 injector, you must access the correct pins on the front harness connector. Knowing which connector is which is critical for electrical diagnosis.
• Main Engine/Body Ground Straps — Key grounds are located near the battery negative terminal, on the passenger side fender/wheel well area, and from the body to the engine block or transmission case.. A poor ground connection can cause erratic behavior in sensors and actuators, including ignition coils and fuel injectors, potentially leading to misfire codes. While less common for a single-cylinder misfire, it should be checked if multiple electrical issues are present.

Real Owner Repair Stories

• RamForum.com user 'Motorhead440' (2016 Ram 5.7L HEMI with 52,000 miles) — Tapping noise, followed by P0301 misfire code.
  ❌ Tried (didn't work) Replaced the internally failed #1 intake lifter (cam was undamaged)., Swapped ignition coils., Swapped fuel injectors.
  ✅ What actually fixed it The P0301 misfire persisted after the lifter was replaced. The final fix was replacing the MDS (Multi-Displacement System) solenoid for cylinder #1. The user suspected the failing solenoid caused the initial lifter failure.
• Reddit user 'Cecil_808' (2012 Ram 2500 6.7L Cummins (relevant diagnostic principle)) — P0301 code appeared the morning after changing the engine compartment fuel filter.
  ✅ What actually fixed it The user cleared the code and it did not return. The likely cause was a small amount of air entering the fuel lines during the filter change, which caused a temporary misfire on startup before the system self-bled.
• RamForum.com user 'Gerald Sheppard' (2008 Ram 1500 5.7L HEMI (relevant cause)) — P0301 misfire code.
  ❌ Tried (didn't work) Repaired a single chewed injector wire.
  ✅ What actually fixed it A squirrel had chewed the injector wire. After one repair, the rodent chewed both wires off the next day. The final fix was replacing the injector connector with a new pigtail and applying pepper spray to the wiring to deter the rodent.

OEM Part Supersession History

• 5149199AA (Ignition Coil, 6.4L HEMI) → 68320417AA — Standard part revision and supplier change over time.
  Heads up: The parts are generally cross-compatible for the specified applications.
• Multiple (Injector, 2019+ 6.7L Cummins) → Bosch 0445124047 (Standard Output), Mopar 68444791AA — Introduction of the 5th generation Ram with an updated Cummins engine and CP4.2 fuel system.
  Heads up: Injectors for 2019+ trucks are not compatible with 2018 and older models. There are also different part numbers for Standard Output and High Output engines.

Model Year Variations Within This Range

• 2019-2020: The 6.7L Cummins engine was updated for the 5th generation Ram. It uses a different high-pressure fuel pump (Bosch CP4.2) and corresponding fuel injectors (e.g., Bosch 0445124047) that are not interchangeable with 2015-2018 models.