P0303 on 2019-2025 Ram 1500: Cylinder 3 Misfire Causes and Fixes

What's Unique About the 2019-2025 Ram 1500

For the 2019-2025 Ram 1500, a P0303 code can point to more than just a simple tune-up part. On the 5.7L HEMI, a misfire on a single cylinder is often an early symptom of a collapsed lifter roller, which then damages the camshaft lobe—a well-documented and serious mechanical issue often called the 'Hemi tick'. Several owners have reported this exact failure sequence, starting with a P0303 code. 🎬 Watch: Real-world diagnosis of a P0303 misfire on a 5.7L Hemi. Additionally, several Technical Service Bulletins (TSBs) have been issued for misfires during cold starts, which may be resolved with a PCM software update rather than a part replacement. On the 3.6L Pentastar V6, cylinder 3 is on the passenger's side bank (front to back: 1, 3, 5), making it relatively easy to access for diagnosis and repair.

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 vibrating idle
• Hesitation or stumbling during acceleration
• Flashing or solid Check Engine Light
• Noticeable loss of engine power
• Decreased fuel economy
• Engine stalling
• Popping sound from engine/exhaust under load

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Ignition coils are a common wear item. Heat and vibration lead to failure over time. Water intrusion from washing the truck has also been reported as a cause of failure for the cylinder 3 coil due to its location near the cowl.
   How to confirm: Swap the ignition coil from cylinder 3 with another cylinder (e.g., cylinder 1). Clear the codes and drive. If the code changes to P0301, the coil is bad. This is the standard first diagnostic step.
   Typical fix: Replace the faulty ignition coil. 🎬 See this walkthrough for replacing ignition coils on your Ram. It is often recommended to replace all spark plugs at the same time.
   Est. part cost: $30-$70 per coil
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Ram specifies long-life iridium spark plugs, but they still wear out or can become fouled by oil or fuel issues. A cracked ceramic insulator from a previous installation can also cause a misfire.
   How to confirm: After confirming the coil is good, inspect the spark plug(s) for wear, fouling (black, oily, or white deposits), or damage to the electrode or ceramic insulator. The 5.7L HEMI uses two plugs per cylinder.
   Typical fix: Replace the spark plug(s) for cylinder 3. It is best practice to replace all 16 spark plugs (on a HEMI) or all 6 (on a V6) at the same time to maintain even performance.
   Est. part cost: $10-$25 per plug
3. PCM Software Update Needed 🟡 Medium Probability Manufacturer TSBs #18-031-25 REV. A and #18-021-26 specifically mention misfire codes (including P0303) occurring during cold start catalyst heating, which can be fixed by reprogramming the PCM.
   How to confirm: This issue typically only occurs during a cold start and may not be present once the engine is warm. A dealership or qualified shop can check if your vehicle's VIN is eligible for the software update mentioned in the TSBs by referencing the bulletin number.
   Typical fix: Reprogramming the Powertrain Control Module (PCM) with the updated software.
   Est. part cost: $0-$200 (dealer labor)
4. Faulty Fuel Injector 🟡 Medium Probability → Shop Fuel Injector
   How to confirm: If swapping the coil and plug doesn't resolve the issue, the fuel injector is the next likely cause. An advanced diagnostic step is to swap the fuel injector from cylinder 3 with another cylinder, but this is a more labor-intensive job. Some owners report this as the fix after ignition parts fail to solve the problem.
   Typical fix: Replace the faulty fuel injector. It's recommended to replace the O-rings and lubricate them upon installation.
   Est. part cost: $50-$120

Rare But Worth Checking

• Failed Lifter / Worn Camshaft Lobe (5.7L HEMI): → Shop Engine Camshaft This is a significant and well-documented issue on HEMI engines, often referred to as the 'Hemi tick'. A P0303 code accompanied by a ticking noise from the engine bay is a strong indicator of this mechanical failure. Multiple owners on forums for 5th Gen Rams have confirmed this failure mode, starting with P0303 and ending with a camshaft and lifter replacement under warranty. A standard compression test may not reveal the issue; a dynamic compression test using an oscilloscope or physical inspection by removing the valve cover is required to see the loss of valve lift.
• Intake Manifold Gasket Leak: → Shop Engine Intake Manifold A vacuum leak near the cylinder 3 intake runner can lean out the air/fuel mixture and cause a misfire. This is more common on higher mileage vehicles and may be accompanied by lean codes like P0171 or P0174.

Diagnosis Steps

1. Read the code with an OBD-II scanner and check for any other stored codes, like P0300 or P219A.
2. Determine your engine (3.6L V6 or 5.7L V8) to locate cylinder 3. On the 5.7L HEMI, it's the second cylinder back on the driver's side. On the 3.6L Pentastar, it's the middle cylinder on the passenger side (front to back: 1-3-5).
3. Swap the ignition coil from cylinder 3 with an easily accessible cylinder (like cylinder 1). Clear the codes and run the engine. If the code moves (e.g., to P0301), the coil is faulty.
4. If the code remains P0303, inspect the spark plug(s) for cylinder 3. Look for wear, damage, or fouling. Replace if necessary.
5. If the coil and plug are good, check the wiring and connector to the coil and fuel injector for any damage or loose connections. Water intrusion has been reported to cause this issue.
6. If the misfire only occurs on cold starts, consult a dealer about TSBs #18-031-25 REV. A and #18-021-26 for a potential PCM update.
7. For 5.7L HEMI engines, listen carefully for a persistent ticking sound, which could indicate the more serious camshaft/lifter failure. This may require removing the valve cover for visual inspection of valve movement.
8. If all else fails, a professional diagnosis involving a fuel pressure test, and dynamic compression/leak-down test may be needed to check for a bad injector or internal engine problem.

Parts You'll Likely Need

• Ignition Coil (5.7L HEMI) (OEM #68238603AA) — This is the most common electrical component to fail and cause a single-cylinder misfire. This part number supersedes 56029129AA, 56029129AB, 56029129AF, and 68060346AA.
  Trusted brands: Mopar, NGK, Denso
  OEM price range: $50-$80
  Aftermarket price range: $30-$60
• Spark Plug (3.6L V6) (OEM #SP149125AF) — Spark plugs are a routine maintenance item. This part number supersedes SP149125AD.
  Trusted brands: NGK, Champion
  OEM price range: $15-$25
  Aftermarket price range: $8-$15
• Spark Plug (5.7L HEMI) (OEM #SP149125AD) — Spark plugs are a routine maintenance item and a primary cause of misfires. The 5.7L HEMI has two per cylinder (16 total). Champion RER8ZWYCB4 is a compatible alternative.
  Trusted brands: Mopar, NGK, Champion
  OEM price range: $15-$25
  Aftermarket price range: $8-$15
• Fuel Injector (3.6L V6) (OEM #05184085AD) — If ignition components are confirmed good, a clogged or failed fuel injector is the next most likely part. This part fits a wide range of 3.6L engines from 2011-2020.
  Trusted brands: Mopar, Bosch, Standard Motor Products
  OEM price range: $80-$150
  Aftermarket price range: $50-$100
• Upper Intake Manifold Gaskets (3.6L V6) — Required when replacing the ignition coils or spark plugs on the driver's side bank (cylinders 2, 4, 6) of the 3.6L Pentastar. Not required for cylinder 3 work alone, but necessary if performing a full tune-up.
  Trusted brands: Mopar, Fel-Pro
  OEM price range: $20-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or affects other cylinders, a P0300 (Random/Multiple Cylinder Misfire) may be stored alongside P0303.
• P0171 / P0174 — If a vacuum leak (like a bad intake gasket) is the cause, lean codes for one or both engine banks may appear with the misfire code.
• P219A — This code for 'Bank 1 Air-Fuel Ratio Imbalance' often appears with a single cylinder misfire on that bank, including P0303, pointing towards a fuel delivery or mechanical issue on that side of the engine.

Technical Service Bulletins (TSBs) & Recalls

• 18-031-25 REV. A: Addresses cold start misfires (including P0303) on 2025 models via a PCM software update.
• 18-021-26: Addresses misfire codes set during cold start catalyst heating, fixable with a PCM reprogram. [NHTSA Data]
• 18-046-24: Mentions multiple cylinder misfire DTCs, including P0303, as part of a list of codes addressed by a software update. [NHTSA Data]
• 09-011-25: Acknowledges P0303 among other misfire codes for 2020 models. [NHTSA Data]

Platform-Specific Known Issues

• Cold Start Misfires: TSB #18-031-25 REV. A and #18-021-26 address misfire codes, including P0303, that can occur during cold start catalyst heating. The fix is a PCM software update, not a hardware replacement.
• 5.7L HEMI Cam/Lifter Failure: A P0303 code, especially when accompanied by a ticking noise, is a very common early symptom of a failed lifter and subsequent camshaft lobe damage. This is a major mechanical repair.
• Water Intrusion: The location of cylinder 3 on the 5.7L HEMI is near the cowl at the back of the engine bay, making its ignition coil connector susceptible to water intrusion after heavy rain or engine washing, which can cause a misfire.

Mechanic-Grade Diagnostic Values

• 3.6L Pentastar Fuel Injector Resistance — expected: 12-14 Ohms (12-12.4 Ohms is common, up to 14 Ohms when warm).. Failure: A significantly higher reading (e.g., 65 Ohms), an open circuit (infinite resistance), or a short (near zero resistance).
• 5.7L HEMI Ignition Coil Primary Resistance — expected: 0.558 - 0.682 Ohms at 70-80°F.. Failure: A reading outside of this specific range indicates a faulty coil winding.
• Ignition Coil Mounting Bolt Torque (5.7L) — expected: 106 In-Lbs (12 N.m).. Failure: Over or under-tightening can lead to improper seating or damage.
• Mode $06 Misfire Counts — expected: Zero or very low counts per cylinder during a drive cycle.. Failure: A high number of misfire counts logged for cylinder 3 (e.g., TID $A5, CID $03) even before the check engine light is triggered, confirms it as the problem cylinder.

Scan Tool Commands That Help

• wiTECH, Snap-on, Autel (professional grade): Cylinder Power Balance Test — This is a crucial diagnostic step when the engine is running. The tool deactivates one cylinder at a time (either by cutting fuel or spark) and measures the drop in engine RPM. A cylinder that causes little or no RPM drop when deactivated is not contributing power and is the source of the misfire. This can quickly confirm the issue is with cylinder 3 before swapping parts.

Wiring & Ground Locations

• Ignition Coil Capacitor — Typically located in the right-rear section of the engine compartment on a mounting stud.. This capacitor dampens electrical noise on the 12V supply wire to the ignition coils. While a failure is rare, a faulty capacitor could introduce electrical interference that might affect coil performance or related sensor readings.
• Main Engine & Body Grounds — The main battery negative cable connects directly to the body and the engine block. Additional ground straps exist between the engine and chassis.. A poor or corroded engine ground can cause a weak spark across all cylinders, but can sometimes manifest intermittently or affect one cylinder more than others due to resistance, leading to a misdiagnosis. Verifying the main grounds are clean and tight is a fundamental step.

Real Owner Repair Stories

• 5thGenRams Forum user 'ITGuy2020' (2019 Ram 1500, 5.7L HEMI, 38,000 miles) — Check engine light with code P0303 that would not clear.
  ❌ Tried (didn't work) Clearing the code with a scanner.
  ✅ What actually fixed it Dealer diagnosed and replaced the camshaft under the powertrain warranty. The user noted that the repair order did not mention lifter replacement, only the camshaft, gaskets, and bolts.
• 5thGenRams Forum user (Ram 1500 Longhorn, 5.7L HEMI, 41,000 miles) — P0303 misfire code.
  ❌ Tried (didn't work) Initial diagnosis was unclear.
  ✅ What actually fixed it The dealership determined the cause was a bad fuel injector. They replaced the injector for cylinder 3, which resolved the misfire.
• RamForum.com user (2010 Ram 1500, 5.7L HEMI) — P0303, rough idle, lurching, poor fuel economy.
  ❌ Tried (didn't work) Fuel additives (Seafoam)., Swapping coil pack from cylinder 3 to 1 (code remained P0303)., Standard compression test (showed 210 PSI, consistent with other cylinders).
  ✅ What actually fixed it A mechanic used an oscilloscope to perform a dynamic compression test, which showed cylinder 3 was losing pressure. The root cause was a failed lifter on cylinder 3 which had destroyed the corresponding camshaft lobe. Replacing all lifters and the camshaft fixed the issue.
• Reddit user r/ram_trucks (2019 Ram 1500 Laramie, 5.7L HEMI) — P0303, very rough idle, and vibration immediately after a thorough truck wash.
  ❌ Tried (didn't work) Swapping the ignition coil with another cylinder; the misfire remained on cylinder 3.
  ✅ What actually fixed it The strong implication, though not explicitly confirmed with a final repair, was water intrusion into the cylinder 3 ignition coil electrical connector. The connector is located near the cowl where water can run off, and the problem started immediately after washing. The fix would be to disconnect, dry with compressed air, apply dielectric grease, and reconnect.

When the Usual Fixes Don't Work

• While ignition coils and spark plugs are the most common culprits for a P0303, multiple owner accounts for the 5.7L HEMI show that these are often replaced needlessly when the true cause is mechanical. In one case, a 2019 Ram with only 38,000 miles required a full camshaft replacement to fix a P0303 code. In another, a bad fuel injector was the final fix after ignition components were suspected. A critical takeaway for HEMI owners is that if swapping the coil and plug doesn't resolve the P0303, the next steps should include listening for engine ticking and considering a faulty fuel injector before assuming it's a simple tune-up issue.

Model Year Variations Within This Range

• 2019-2025: The presence of the 5.7L HEMI with eTorque mild-hybrid system became more common. For a P0303 diagnosis, it's important to know that the eTorque system's 48V belt-starter generator is used for auto start/stop restarts, but a conventional 12V starter is still used for initial cold starts. Therefore, a starting issue on a cold engine is unlikely to be related to the eTorque MGU itself.
• 2019-2025: As shown in the provided TSBs, the PCM software has been revised multiple times to address misfires during specific conditions like cold start catalyst heating. A 2020 model may have different software from a 2024 model, making a dealer software update a necessary diagnostic step, especially for cold-start-only misfires.